3.1. General description and concepts
3.2. Relevance and magnitude
Livestock - environment interactions are caused by direct or indirect effects, either positive or negative. Chapter 1 has already illustrated that indirect effects caused by LLM systems occur as a result of the production of inputs or as a result of the processing of outputs. Direct effects result from the use of inputs in LLM systems themselves (see Figure 2). Accordingly, we will briefly consider the indirect environmental effects occurring before entering or after leaving LLM systems following which direct environmental effects occurring within LLM system will be dealt with more thoroughly. An advantage of this approach is that the environmental effects occurring in the different stages can be clearly linked with certain actors, which may benefit the development of adequate (i.e. efficient and effective) policies (see Chapter 4).
As stated in Chapter 1, there are a number of issues that although typically related to LLM systems do not directly cause environmental problems. These issues (the possible contribution of LLM systems to genetic erosion, the induced competition between food and feed, food safety problems and problems associated with animal welfare and high consumption levels of livestock products) are not described in this section but discussed in section 3.2.
Environmental effects occurring before entering LLM systems
Environmental effects occurring before entering LLM systems are related to the production of concentrates: one of the main inputs in LLM systems. The production of concentrates may be divided into four different stages:
- agricultural production of feedstuffs;
- transport of feedstuffs to feed processing industries;
- processing of feedstuffs to concentrates in the feed processing industries; and
- transport of concentrates to the farms.
Each of these four stages has some impact on the environment. A thorough discussion on these impacts is beyond the scope of this study; we refer to Hendy et al. (1995). Only a brief overview is given here. The demand for concentrates in LLM systems induces increases in cropped areas, intensities and yields. The environmental impacts include general effects of increased crop production on changes in land use: increased pressure on other forms of land use, resulting in deforestation, change of habitats and reduced biodiversity. The cultivation of the crops themselves results in effects on soils, water and the atmosphere, caused by the use of e.g. fertilizers and pesticides/herbicides. Environmental effects occurring during the transport and processing stages, mainly concern fossil energy use and some processing wastes and pollutants. The latter are not significant for most feed commodities. Where wastes do constitute a nuisance, they are generally the products of processing of materials for food or industrial uses. Modern processing of compound feeds does not create waste or environmental impacts other than those from fossil energy consumption (Hendy et al., 1995).
Environmental effects occurring within LLM systems
Negative environmental effects occurring within LLM systems are largely related to the use of fossil energy and concentrates. Most effects are caused by various emissions from manure in stables, during storage, after application on soils or when manure is simply disposed of. Below we will deal with various emissions of nitrogen, phosphorus, carbon, and some heavy metals (copper, zinc and cadmium).
Nitrogen and its pathways
Nitrogen enters LLM systems via the use of concentrates. It may leave LLM systems in the form of useful products (eggs, meat) or in the form of emissions. Nitrogen exists in many chemical forms, either in organic compounds (mainly proteins) or in mineral compounds. Organically bound nitrogen is relatively immobile, but mineral nitrogen is very mobile and easily emits to the external environment. Mineral nitrogen may occur as NH4+, NH3, N2, N2O, NO, NO2, NO2- and NO3-.
Volatilization of ammonia
Ammonia (NH4+), abundant in manure, easily converts to the highly volatile NH3. NH3 is emitted when the manure is in contact with air: in stables, in manure storages (upper layer of the manure) and during and after application of manure on soils. For a description of the chemical processes involved, we refer to Brandjes et al. (1995). Emission of NH3 is undesirable because it has toxic, eutrophic and acidifying effects on ecosystems (Wilson & Skeffington, 1994a and 1994b). Because emitted ammonia tends to deposit in the surroundings of its source (i.e. within several kilometres), it is particularly harmful if ecosystems, which are vulnerable to acidification and eutrophication, are located nearby. The possible degradation of such an ecosystem is of course strongly related to total annual ammonia emission, which is dependent on livestock densities in a certain area.
Within closed stables, concentration of ammonia may reach high levels, resulting in toxic effects on the housed animals and the humans working in them.
Volatilization of N2, N2O and NOx
Under aerobic conditions, particularly after application of manure on soils, the ammonia in manure is transformed into nitrate (NO3-) by micro-organisms (nitrification). Under anaerobic conditions (during storage or anaerobic processing of manure), ammonia is transformed to N2 (denitrification). Both during the nitrification and the denitrification process, in addition to the end products (respectively NO3- and N2), also N2O, NO and NO2 are formed. The ratio between the formation of these “by-products” and the formation of the end products is very variable and is dependent on many variables (e.g. temperature, humidity and pH). The emission of N2O is particularly harmful to the environment, it contributes both to global warming and breakdown of the ozone layer.
Runoff and leaching of nitrate and other N compounds
As stated, NO3- is formed out of NH4+ under aerobic conditions, particularly after application of manure. NO3- and NH4+ are highly soluble in water and could be transported in water. There are two transport routes by which both N-compounds may be emitted to the external environment. First route is via runoff. Factors influencing losses by runoff are: rate of manure application, total amount and intensity of precipitation, infiltration capacity of the soil and slope of the soil surface.
Once percolated into the soil, NH4+ is reasonably bound by soil particles, but not NO3-. Thus, if NO3- is not absorbed by plant roots, it may leach to the higher ground water levels and from there be transported to deeper ground water levels or to surface waters. Leaching occurs in cases of a precipitation surplus (i.e. when precipitation is higher than the water holding capacity of the soil plus evapotranspiration by soil and crops). Part of the leached NO3- may be transformed to N2 by the denitrification process (particularly in water saturated soils, under anaerobic conditions). However, in general most of it ends up in ground water.1
1 It has been suggested that aquifers polluted by agricultural, livestock and other effluents may emit large amounts of N2O (Ronen et al., 1988, cited by Chen, 1990).
Manure storage installations may cause nitrogen leaching and run-off as well. Concrete liquid slurry tanks are often not completely waterproof and contact with ground water does occur. Manure stored in lagoons may cause high nitrogen emissions, the extent somewhat depending on the lining of the lagoon.
Run-off and leaching of nitrogen directly lead to eutrophication of surface waters, and via seepage water, to eutrophication of nature reserves. In several countries the NO3- levels in drinking water sources exceed health standards.
Phosphorus
Phosphorus enters LLM systems through the use of concentrates. Unlike nitrogen, phosphorus is not very mobile and is easily bound in soils. Therefore leaching of phosphorus hardly occurs. Emission of P is caused by run-off. Emission of P causes eutrophication of surface waters. Some soils are saturated with P. This saturation is caused by long-term high P-application rates, exceeding crop uptake. In P-saturated soils leaching of P does occur, because the binding capacity of the soil is exceeded.
Odours
Animal manures contain volatile organic compounds, of which a significant proportion is made up of volatile fatty acids. The major constituent of these volatile fatty acids is acetic acid. Other aromatic compounds include phenol, cresol and skatol. Chemical analysis of the constituents of odours from several animal manures, has revealed over a hundred different compounds, which, blended together, produce the typical odour of manure. The concentration of an odour is affected by the number of animals and the handling and storing practices of the manure.
Carbon compounds
Two carbon compounds that are harmful to the environment are emitted in LLM systems. Carbon dioxide (CO2) is emitted through the use of fossil energy (for e.g. heating or mechanical ventilation of stables). Methane (CH4) is emitted from two sources in LLM systems: from digestive processes in animals and from anaerobic decomposition processes of organic matter in manure. In LLM systems the latter source is far more important. Emissions of carbon dioxide and methane both contribute to global warming. Methane also plays a role in the breakdown of the ozone layer. Anaerobic decomposition of manure may be stimulated in manure processing installations to produce methane. The methane produced is used as an energy source.
Heavy metals
Heavy metals of concern in LLM systems are copper, zinc and cadmium. They are introduced in LLM systems through concentrates, but in different ways. Cadmium is a pollutant of phosphate minerals which are added to concentrates as mineral mixtures, in order to meet the phosphate requirements of animals. Copper and zinc are essential minerals for animals and deliberately added to feeds, above the animals’ requirements. Copper is not only an essential mineral, but also has a stimulating effect on growth performance. More than 95% of copper and zinc intake is excreted via the faeces. Heavy metals are generally bound to the soil, but it has been found that continuous loading over a long period will result in a build up to toxic levels.
Environmental effects occurring after leaving LLM systems
Environmental effects occurring after leaving LLM systems are related to the processing of useful outputs from LLM systems: animal products. This processing takes place in slaughterhouses and/or animal processing industries, during which all kinds of waste is produced in the form of solid material, as volatile compounds that are discharged into the air, or, most important, as waste-water.
Waste-water may originate from water used in the processes adopted in slaughterhouses and from water used for general cleaning operations. Waste-water from slaughterhouses again contains a wide variety of compounds, but all of an organic nature and all highly biodegradable. These organic substances in waste-water are subject to degradation by micro-organisms. Most common micro-organisms present in the aquatic environment require oxygen for this degradation process. The amount of oxygen needed for the micro-biological degradation of organic substances is expressed as biological oxygen demand (BOD). In cases where surface waters contain high amounts of easily degradable organic substances, oxygen shortages in the surface water may result. Hence, all biological life in such surface waters is destroyed and purification of organic matter under anaerobic conditions results, causing bad odours as well as sanitary problems. Processes involved in anaerobic breakdown of organic matter in surface water show positive feedback mechanisms, thereby accelerating the process. Discharge of volatile compounds from slaughterhouses causes bad odours in the immediate surroundings. Other forms of air pollution are related to the utilization of fossil energy during processing and transport of products from LLM systems (causing CO2 emission).
Solid waste mainly consists of the discarded parts of animals (heads, combs, hoofs, bones, feathers and organs). The environmental impact of this solid waste depends on the extent to which it is used in e.g. animal feeds or other useful applications.
3.2.1. Introduction and methodology
3.2.2. N and P excretion by pigs and poultry in LLM systems
3.2.3. Manure management systems
3.2.4. Emissions from stables and during storage of manure
3.2.5. Emissions after manure application to land
3.2.6. Fossil energy consumption
3.2.7. Heavy metals in LLM systems
3.2.8. Methane emission from LLM systems
3.2.9. Wastes from animal processing
3.2.10. Competition between food and feed
3.2.11. Food safety
3.2.12. Animal genetic resources and LLM systems
3.2.13. Associated problems: Animal welfare and high consumption levels of livestock products
Proper quantification of livestock - environment interactions should consider (Willeke-Wetstein et al., 1994):
- nutrient cycles with emphasis on potential nutrient losses;
- production processes with possible ecotoxic effects;
- energy flows; and
- resource use and conservation, including soil, water and genetic resources.
Significant problems arising while quantifying the livestock - environment interactions are related to the definition of indicators and the availability and reliability of data. In order to quantify livestock - environment interactions, FAO selected a number of key indicators and their parameters, applied to LLM systems. Distinction is made between direct indicators (either of a physical or biological nature) and indirect indicators (either of an agricultural or socio-economic nature). These indicators and their parameters are listed in Annex 3, on which the assessment of livestock - environment interactions in the rest of this Chapter will be based. We have chosen to deal implicitly with these key indicators and their parameters in the light of the major issues concerning LLM systems and the environment. We divided them into two categories: issues related to N and P emissions from manure, and other issues. Issues belonging to the first category are dealt with as follows. Firstly, a system-wide estimate is made of the total N and P excretion by animals in LLM systems. Then, a system-wide estimate is made of the use of various manure management systems in use throughout the world and a system-wide estimate of the N and P losses occurring from these systems. Thus, some insight can be obtained in total N and P losses (i.e. emissions) before any form of manure application to land. The magnitude of these N and P losses will be related to the fossil energy and monetary costs needed to produce the equivalent amount of artificial fertilizer. Emissions of N and P occurring after manure application to land is only dealt with in a case study approach, because the intensity of manure application, and thus the occurring emissions, are unknown (see section 3.2.5.).
Other issues considered are the use of fossil energy, heavy metals, methane emission, wastes from animal processing, competition between food and feed, food safety problems, LLM systems and animal genetic resources and finally problems related to animal welfare and high consumption levels of livestock products. Owing to a general lack of data, most of these issues are dealt with in a case-study approach (fossil energy use, heavy metals), a semi-quantitatively approach (competition between food and feed), or even in a qualitative approach (animal genetic resources, food safety, animal welfare/high consumption levels). Exceptions are methane emission and wastes from processing, which are estimated system-wide.
The amount of N and P excreted in animal manure depends on the species and age of the animal and the composition of its diet (corresponding with the production level of the animal; Faassen & van Dijk, 1987). Species relevant to LLM systems are pigs, laying hens and broilers. Pigs and laying hens were further categorized into growing pigs and sows, and growing laying hens and productive laying hens respectively. Moreover, a differentiation was made between estimated N and P excreted by pigs in faeces and that excreted in urine, as management for both types of excreta may be very different. For each animal category, three feeding management systems were identified. These three feeding management systems are based on data from Canada, the Netherlands and tropical countries, respectively. The feeding management systems differ with respect to feed composition and, thus, feed conversion and N and P content and digestibility. On the basis of the three identified feeding management systems for each animal category and data on pork, poultry meat and egg production provided by Sere & Steinfeld (1995), average annual N and P excretion in LLM system is calculated. Results are given in Table 3.3. Annex 4 gives all the calculations and the underlying assumptions (with respect to feed composition, feed conversion ratios, feed intake, calculation of parameter world averages, etc.).
Safley et al. (1992) investigated the manure management systems in use in the various regions of the world, for several types of animals, including pigs and poultry. Before quantifying manure management in LLM systems based on their data, a general description of the major pig and poultry manure management systems in use is given below.
- Manure in solid storage systems is managed by collecting only the faeces produced, with or without bedding, by some means such as scraping. The collected faeces is stored in bulk for a long period of time (months) before any disposal. Urine, not collected at all in this system, percolates via run-off into the soil or enters surface waters. Solid storage is particularly common in Asian regions, where the faeces may be dried and collected in bags and sold in markets for e.g. gardening purposes (pers. comm. Gijsberts, 1995). Manure stored in solid storage systems may have a dry matter content of up to 40-50%.- In liquid/slurry systems, the animals are kept with little or no bedding material. Manure is separated from the animals by slatted floors or open channels. Manure in liquid/slurry systems is stored in large concrete-lined tanks beneath the building or outside. It may be stored in the tank for six or even more months until it is applied to fields. In liquid/slurry systems the manure stored usually has a dry matter content of less than 12%. The reason for this low dry matter content is that water is added to the manure, e.g. when stables are flushed or by spilled drinking water. This system is often used for pigs and laying hens.
- Lagoon systems are generally characterized by automated flush systems that use water to transport the manure to treatment lagoons that are usually deeper than six feet. The manure resides in the lagoon for periods ranging from 30 days to over 200 days depending on the lagoon design and other local conditions. The water from the lagoon is often recycled as flush water or may be used for irrigation on fields, then providing fertilizer value. Lagoons may be subject to overloading and periodic odour problems. In lagoons high nitrogen losses occur. Schulte (1993) mentions a total N loss of 70-80% of the total N in manure before any form of application.
- Liquid/slurry manure may be placed in an anaerobic digester for treatment. Although digester designs vary, all have the objective of producing methane for energy and reducing the volume of the waste. The amount of usable methane produced depends on the operating characteristics of the digester and the characteristics of the manure. The digester effluent is often used as a fertilizer.
- The manure of caged laying hens is collected in solid form in deep pit stacks below the cages. The manure in the pits may only be removed once a year. According to Safley et al. (op.cit.), this manure generally stays dry, though not sufficiently dry (over 70% DM) to prevent high ammonia losses (Faassen & van Dijk, 1987).
- Broilers and pigs may be kept on litter (e.g. shavings, sawdust or peanut hulls). The combined manure and litter is allowed to accumulate within the building, only being removed at the end of the production cycle (broilers), or when the layer becomes too thick for the animals.
- Finally, manure may be collected, dried in cakes and burned for fuel, for example for heating and cooking. This system is common in Asia and the Far East.
The estimates for the percentages of total pig and poultry manure managed in each of the different systems, as given by Safley et al., are shown in Table 3.1. It must be emphasized that Safley’s estimates are not necessarily always valid for LLM systems. This is especially true for pigs, because the share of pork produced in LLM systems is only about 40% of total pork production (see Table 2.1). The percentages given by Safley et al. for poultry production will more closely reflect the situation in LLM systems, because the share of poultry meat and eggs produced in LLM systems amounts to 70% of total production (see Tables 2.2 and 2.3). Safley’s estimates form a good basis to make estimates for manure management systems in use for LLM systems. These are also given in Table 3.1. The underlying assumptions are given below.
The following are the assumptions for pig manure management in LLM systems:
1) In some countries manure is not managed at all, but directly discharged into surface water. For example in Hungary, every year 45-50 million cubic metres of liquid pig manure is produced of which 20-22 million cubic metres are applied in agricultural areas. The remainder (of which the fate is unknown) could cause an enormous environmental problem (Wachtler & Turanyik, 1993). It seems reasonable to assume that at least part is directly discharged into surface waters. Vighi & Chiaudani (1985) suspect that in Italy in the seventies up to 10% of the liquid animal manure was directly discharged into surface water. More recent data have not been found. In the Beijing area there are about 3,000 large-scale chicken and pig farms, with on average 49,000 chickens or 22,000 pigs per farm. It is known that 80% of the manure produced on these farms is partly directly spread on fields, but also released into rivers without any treatment, causing serious pollution to the air nearby, to rivers and to underground water (Shaoqi, 1994). One more example is Slovenia in the part which belongs to the Danube catchment. Here, the larger pig farms do not have enough land to apply manure in the recommended time and dose. After primary coarse separation of some solids, manure may end up in streams (Anonymous, 1993b). In cases like this it becomes unclear whether to speak of treated manure or directly discharged manure.Based on the examples given above, we estimate that 1% of pig manure produced in LLM systems is more or less directly discharged into surface waters.
2) We believe that the percentage given by Safley et al. (op.cit.) for solid storage in general is too high, and especially when applied to LLM systems. For example Safley et al estimate that, in most OECD countries, the amount of pig manure managed in the solid storage system is about 25%, but this is much too high. The probability of an overestimation of the solid storage system might also be illustrated by the situation in Lithuania. In this country some 65% of the manure was handled in solid storage systems and 35% in liquid systems. The latter percentage originated mainly from the large pig complexes (Schillhorn van Veen, 1994). It illustrates that with increasing intensity of pig production the system changes from solid manure to a (less time-concerning) liquid system.. We estimate that only 10% of the pig manure produced in LLM systems is treated in solid storage systems.
3) Safley et al. (op.cit.) estimate that on a global level 5% of the pig manure is treated in lagoons. The average percentage given for North America (25%) probably reflects the real situation quite well, because here sufficient data were available. But we expect that this is not the case with the percentages mentioned for important pig producing regions like Eastern Europe and Asia (8 and 5% respectively). In Southeast Asia, storage (or disposal) in lagoons is quite common (pers. comm. Gijsberts, 1995) and its frequency will be higher than 5%. For the situation in EE, we refer to Anonymous (1994a) and related studies (Anonymous, 1993b and Varduca, 1994). They calculated nutrient loads polluting the Danube river from several Eastern European countries. Animal production in these countries accounts for most of the nutrient load. For example in Romania, the large-scale state farms are provided with “waste treatment plants”, i.e. lagoons. The effluent of these lagoons is not used for irrigation, but directly discharged into the surface water. On the smaller (private) animal farms, accounting for 75% of all animal farms, all manure is used for agricultural purposes (Varduca, 1994). In Slovenia the situation is more or less the same. The large-scale pig farms, accounting for 77% of the national pig stock, discharge the effluent of partially treated manure into the surface water (Anonymous, 1993b), thereby assuming that this treatment takes place in lagoons. The overall picture for EE may be summarized as follows. In a number of countries, large-scale livestock farms face problems with disposal of the manure. Manure is still discharged in a more or less pre-treated form (treatment mainly in lagoons) into surface waters (Anonymous, 1994a).
Based on the above we assume that at least 10% of the pig manure produced in LLM system is managed in lagoons.
Table 3.1: Percentages of total pig and poultry manure managed in different manure management systems..1 Percentages of total pig and poultry manure managed in different manure management systems. (Adapted from Safley et al. (1992) and own estimates; explanation: see text)
|
|
lagoons |
liquid systems |
solid storage |
used for fuel1 |
deep pit stacks and litter |
||
|
Safley et al.2 |
|
|
|
|
|
|
|
|
pigs |
5 |
42 |
45 |
3 |
|
53 |
|
|
poultry |
1 |
8 |
<1 |
1 |
|
57 |
|
|
|
lagoons |
liquid systems |
solid storage |
anaerobic digester |
burned for fuel |
deep pit stacks and litter |
directly discharged |
|
Authors’ estimates |
|
|
|
|
|
|
|
|
pigs |
10 |
71 |
10 |
1.5 |
1.5 |
53 |
1 |
|
broilers |
- |
- |
- |
- |
- |
100 |
- |
|
laying hens |
1 |
77 |
<1 |
|
1 |
20 |
- |
1 Includes anaerobic digesters and burned for fuel.2 Both rows containing estimations given by Safley et al. do not add up to 100. Reason is that only estimates are given for manure management systems which are relevant in LLM systems. For example, the percentage Safley et al. give for the daily spread system is not given, because that system is considered not to be relevant LLM system.
3 Concerns pig manure in litter system.
4) The percentages Safley et al. (op.cit.) give for pig manure used for fuel or managed in litter systems are not significant. We did not find data that allow us to make a more accurate estimate for manure managed in these systems, so we adopted Safley’s data for these systems. Of manure used for fuel, it is assumed that half of it is placed in an anaerobic digester and half of it is burned for fuel.
5) The remainder (71%) is assumed to be managed in liquid systems.
For manure from laying hens in LLM systems the assumptions are:
1) Deep pit stacks and litter are significant in OECD countries. Therefore it is assumed that 20% of the manure from laying hens is managed in this system.2) Safley’s percentages for the relatively insignificant manure management systems (lagoons, solid storage and used for fuel) are assumed to be valid for laying hens in LLM systems as well. Additional assumption is that manure from laying hens used for fuel is not placed in anaerobic digesters, but only burned for fuel.
3) The remainder (77%) is assumed to be managed in liquid systems.
For broiler manure management in LLM systems, we assume that only the litter system is used (Smith, 1990 and WUMM, 1994).
Emissions of P from stables and during storage of manure occur when solid storage or lagoon systems are practised, or when manure is burned for fuel. However, data on P emissions from these systems have not been found. We made the following assumptions:
- Emissions of P from poultry manure are negligible in the main manure storage systems. Only P emissions from pig manure have been taken into account.- It is known that lagoon systems may be subject to overloading, for example because of excessive rainfall. Depending on the lining of lagoons, P emission into soils may occur as well. We assume the P emission from lagoon systems to be 10% of the total P excreted in pig manure.
- The P emissions from solid storage systems will mainly be from urine P. Here, we estimate P losses from urine excreted in pig manure managed in solid systems at 100%. Because this is probably an overestimate of real P losses from urine, we compensate this overestimate by not taking into account P losses from faeces.
- If pig manure is burned for fuel, only faeces are used. Like for the solid storage system, we therefore assume that all urine P is emitted to the environment.1
1 If ash is not recycled, P excreted in faeces will be lost as well.
To a large extent, N losses from stables and during storage occur in the form of ammonia. Ammonia formation in manure is determined by the sum of easily available nitrogen (urea, uric acid and ammonia). Next to the ammonia concentration in manure, emission is determined by the contact between manure and air, pH of the manure, and humidity of the manure (Brandjes et al., 1995). These factors vary enormously for each of the different manure management systems. In developed countries, research has been carried out to determine the occurrence of N losses in the form of ammonia in stables and during storage of manure. Some results for liquid systems and deep pit stacks are given in Table 3.2. Based on the emission factors given in Table 3.2, we assume that N losses from pig manure in liquid systems amount to (0.5 * (0.21+0.16) + 0.15) * total N excretion. For manure from laying hens managed in deep pit stacks or litter, the emission factor can directly be derived from Table 3.2, and amounts to 0.5 * total N-excretion. Consequently, we assume that N emission from laying hens in litter equals N-emission from broilers housed in litter systems. For manure from laying hens managed in liquid systems the emission factor is 0.11 * total N excretion.
Losses during the storage phase may not only occur in the form of ammonia. This is especially true for manure in solid storage and lagoon systems and when manure is used for fuel. Data on N losses from solid storage and lagoon systems are also given in Table 3.2 based on NARC (1989) and Schulte (1993). Losses from the solid storage system, other than in the form of ammonia, will mainly be from N in urine,, leaching into soils and surface waters. Just like P, we set N losses from pig manure in solid storage systems at 1.0 * N in urine. Owing to a lack of data and because of its insignificance N losses from manure from laying hens in solid systems are ignored.
For manure from laying hens and from pigs managed in lagoons, we adopt an emission factor of 0.75 * total N excretion. As stated, N losses from lagoons may be due to overloading by an inadequate lining of the lagoon or emitted as NH3, N2, N2O or NOx.
Most of the Nitrogen in liquid pig manure that is treated in anaerobic digesters will be emitted to the environment as N2, because under anaerobic conditions denitrification occurs. By-products will be N2O and NOx. It is assumed that 80% of the N in liquid manure treated in anaerobic digesters will be emitted to the environment. We assume that all N is lost when manure from pigs and laying hens is burned for fuel. Part of the N losses from pig manure will be from urine (which is not collected when manure is burned) and part from faeces, which will be emitted to the atmosphere during the burning process.
Data in Table 3.2 all refer to temperate zones. No data have been found on N losses from stables and during storage in tropical areas. Brandjes et al. (op.cit.) state that emissions are likely to be higher in regions with higher average annual temperatures, not only because of higher temperatures, but also because of more aeration in stables. Thus, the estimates given might underestimate the reality to some extent.
Table 3.2: N losses from stables and storages.2 N losses from stables and storages (as fraction of N excreted by animals)
|
|
pigs |
sows |
layers |
broilers |
not specified |
source |
|
liquid systems |
|
|
|
|
|
|
|
stable |
0.21 |
0.16 |
0.11 |
|
|
Brandjes et al. (1995), based on Monteny
(1991) |
|
storage |
0.15 |
|
|
|
|
id. |
|
placed in anaer. digester |
0.80 |
|
|
|
|
authors’ estimate |
|
deep pit stacks & litter |
|
|
|
|
|
|
|
stable |
|
|
0.50 |
0.10 |
|
Monteny (1991) |
|
storage |
|
|
|
0.40 |
|
id. |
|
solid storage |
|
|
|
|
|
|
|
litter/manure pack |
|
|
|
|
0.20-0.40 |
NRC (1989) |
|
lagoon |
|
|
|
|
0.70-0.80 |
id. and Schulte (1993) |
From Table 3.3 it is obvious that especially N losses from manure before any form of application are high (a calculated 44, 50 and 20% of N excreted by pigs, broilers and laying hens respectively). It must be emphasized that most of these N losses are harmful to the environment, but not all, depending on the form in which the losses occur, which is different for each manure management system. It is clear that N losses due to direct discharge of manure will all have detrimental effects on the environment. Most of the N managed in liquid systems will be emitted in the form of ammonia, and thus, N losses from liquid systems (accounting for some 40% of total N-losses) will also be more or less harmful to the environment. In solid storage systems, N losses from urine occur largely in two forms: as ammonia (to the atmosphere) or as NO3- (to ground water or surface water).
Table 3.3a: Total N and P excretion by pigs in LLM systems and losses occurred before any form of application.3a Total N and P excretion by pigs in LLM systems and losses occurred before any form of application (in ton*yr-1)
|
PIGS |
||||||
|
Nitrogen |
||||||
|
|
Total N excretion |
N excretion in urine |
N excretion in faeces |
managed in: |
adopted emission factor |
N loss |
|
|
354131 |
262544 |
91587 |
lagoons |
0.75*total N |
265599 |
|
|
2514333 |
1864065 |
650268 |
liquid systems |
(0.19+0.15)* total N |
854873 |
|
|
354131 |
262544 |
91587 |
solid storage |
1.0*urine N |
262544 |
|
|
53120 |
39382 |
13738 |
anaerobic digester |
0.8*total N |
42496 |
|
|
53120 |
39382 |
13738 |
burned for fuel |
1.0*total N |
53120 |
|
|
177066 |
131272 |
45794 |
litter |
0.3*total N |
53120 |
|
|
35413 |
26254 |
9159 |
directly discharged |
1.0*total N |
35413 |
|
TOTAL |
3541314 |
2625444 |
915870 |
|
0.44*total N |
1567165 |
|
Phosphorus |
||||||
|
|
Total P excretion (tons P*yr-1) |
P excretion in urine (tons
P*yr-1) |
P excretion in faeces (tons
P*yr-1) |
managed in: |
adopted emission factor |
P loss (tons P*yr-1) |
|
|
92534 |
12866 |
79669 |
lagoons |
0.1*total P |
9253 |
|
|
656994 |
91346 |
565649 |
liquid systems |
- |
- |
|
|
92534 |
12866 |
79669 |
solid storage |
1.0*urine P |
12866 |
|
|
13880 |
1930 |
11950 |
anaerobic digester |
- |
- |
|
|
13880 |
1930 |
11950 |
burned for fuel |
1.0*urine P |
1930 |
|
|
46267 |
6433 |
39834 |
litter |
- |
- |
|
|
9253 |
1287 |
7967 |
directly discharged |
1.0*total P |
9253 |
|
TOTAL |
925343 |
128656 |
796688 |
|
0.036*total P |
33302 |
Table 3.3b: Total N and P excretion by poultry in LLM systems and losses occurring before any form of application.3b Total N and P excretion by poultry in LLM systems and losses occurring before any form of application
|
BROILERS |
|||||
|
Nitrogen + phosphorus |
|||||
|
|
Total N excretion (tons N*yr-1) |
Total P excretion (ton P*yr-1) |
managed in: |
adopted N emission factor |
N loss (tons N*yr-1) |
|
|
s |
481627 |
litter |
(0.10+0.40)* total N |
863092 |
|
TOTAL |
1726184 |
481627 |
|
0.50*total N |
863092 |
|
LAYING HENS |
|||||
|
Nitrogen + phosphorus |
|||||
|
|
Total N excretion (tons N*yr-1) |
Total P excretion (tons P*yr-1) |
managed in: |
adopted N emission factor |
N loss (tons N*yr-1) |
|
|
16473 |
5194 |
lagoons |
0.75*total N |
12355 |
|
|
1268392 |
399943 |
liquid systems |
0.11*total N |
139523 |
|
|
<16473 |
<5194 |
solid storage |
not considered |
- |
|
|
16473 |
5194 |
burned for fuel |
1.0*total N |
16473 |
|
|
329452 |
103881 |
deep pit stacks + litter |
0.5*total N |
164726 |
|
TOTAL |
1647262 |
519407 |
|
0.20*total N |
333077 |
|
Total for pigs, broilers and layers in LLM systems |
6914760 |
1926377 |
|
0.36*total N |
2763334 |
Thus, total N losses in LLM systems theoretically induce an extra fossil energy requirement of 50 * 2,763,334 * 1000 = 1.38*1011 MJ*yr-1 for the production of artificial fertilizer. Assuming a world market price of US$ 365 per ton N in artificial fertilizer, some US$ 1,010*106 are lost.
In LLM systems P losses from manure before any form of application are much lower than for N. But assuming fossil energy requirement for P in artificial fertilizer to be 4.37 MJ*kg-1 P and a world market price of US$ 430 per ton P (Brandjes et al., 1995), P-losses in LLM systems induce an extra fossil energy consumption of 1.46*108 MJ*yr-1 and a loss of US$ 14*106.
In recent years many measurements have been taken of the emission of ammonia from pig- and poultry manure during and after surface spreading on soils. An overview of the results is given by Monteny (1991). Ammonia emission during application is low in general and amounts to 1%. Ammonia emission after application is much more important and is determined by the type of manure, weather circumstances, applied dose and soil and crop characteristics. Due to these determining factors, an enormous variation exists. Ammonia emission from liquid pig manure ranges between 40-98% of the total ammonia content of the applied manure. For manure originating from laying hens, the range is between 21-36%. Applying broiler manure brings an ammonia emission of about 24% of total ammonia content with it. A thorough discussion on emission of ammonia after manure application is given in Nielsen et al. (1991).
Recently, Bouwman (1995) has made a global estimate for N2O emissions from animal manure. N2O emission was assumed to be 1% of N excreted in manure. Global N excretion by the world livestock population was estimated to be 100 million tons (van der Hoek, 1994; cited by Bouwman, 1995), resulting in a global N2O emission of 1 million ton N2O-N1. Because total N excretion in LLM system amounts to 6.9 million tons*yr-1 (see Table 3.3), it can be argued that N2O emission from LLM systems constitutes 6.9% of global N2O emission from animal manure. However, since anaerobic conditions are more likely in LLM systems (with high animal densities housed in confinement and large amounts of manure stored in liquid systems) than in more extensive systems, N2O emissions per kg of N excreted can be expected to be relatively higher.
1 Bouwman (1995) concludes that animal excreta form a significant global source of N2O. The global amount of N in animal excreta about equals the N applied as artificial fertilizers, indicating a possible contribution to the global N2O budget of the same order of magnitude. A growing world population will inevitably lead to an increasing input of N in the form of fertilizers and it will thus be difficult to mitigate N2O emissions related to food production. Bouwman states that important reductions could be achieved by a shift-away from animal production, which reduces both artificial fertilizer use and production of animal excreta.
It is very difficult to estimate how much nutrient will be used by crops and how much nutrient will pollute the environment in the form of emissions after manure application. Emissions to soil and water, occurring after application of manure to land are, like for ammonia emission, determined by type of manure, weather circumstances, applied dose, and crop and soil characteristics. Therefore a system-wide quantification of the various emissions of N and P to soil and water is not feasible. For a discussion on N losses through run-off and leaching in relation to applied dose, soil characteristics and weather circumstances, we refer to Brogan (1981) or Calvet (1990). An overview of water pollution problems in many European countries is given in Esselink et al. (1991) and CEC (1989), also in relation to animal manure. For the situation in the USA we refer to Blake et al. (1992). Though we have chosen a case-study approach, it can be stated that in general emissions from manure produced in LLM systems are relatively high: manure production in LLM systems is concentrated in small areas, the manure is more or less seen as a waste, resulting in manure dumping or at least application of high doses per unit of land, not always under favourable conditions.
Emissions of N and P to water: the example of Brittany
Brittany is divided up into four Departments, i.e. Côtes du Nord, Finistère, Ille-et-Vilaine and Morbihan. Compared with the rest of France, the animal densities in Brittany are high. The number of pigs, cattle and poultry in Brittany accounts for 50, 13 and 38% respectively of the French total. Among the four departments in Brittany, differences exist in the importance of the various animal production systems. Pig and poultry production are both important in Cotes du Nord and Finistère, whereas cattle is more important in Ille-et-Vilaine. Morbihan is in between. High animal densities mean high manure production. In 1982, N excretion by all livestock in Brittany amounted to 134 kg N/ha. The shares from pigs and poultry were 22 and 14% respectively. The remaining 64% was produced by cattle (Brouwer et al., 1992). This shows that pollution caused by manure cannot be considered, without taking into account the presence of other livestock. In Brittany, it is the combination of the two types of production, plus the application of artificial fertilizers, that contributes to the magnitude of water pollution. Pollution causes high nitrate levels in drinking water and eutrophication of inland surface waters and marine ecosystems. Nitrate levels in drinking water have recently been increasing. Whereas in the early eighties only Nord-Finistère showed a nitrate concentration of over 50 mg nitrate per litre, now five other regions in France have exceeded this limit and many others are over the 40 mg mark (Rainelli, 1991 and OECD, 1989). Eutrophication of marine ecosystems causes algae growth, which is a problem for shellfish growers. Shellfish in the Saint-Brieuc Bay (north of Côtes du Nord) are contaminated with bacteria (partly with faecal streptococci from animal origin) and sale of the mussels is forbidden (Rainelli, 1991).
In Table 3.4 data on animal densities and nitrogen transfers through the environment are given for Brittany and its sub-regions.
Table 3.4: Animal densities (1988) in some regions of Brittany and nitrogen transfers through the environment.4 Animal densities (1988) in some regions of Brittany and nitrogen transfers through the environment
|
|
Cotes du Nord |
Finistère |
Ille et Vilaine |
Morbihan |
Brittany (total) |
|
|
Animal densities (animals per ha UAA)
|
||||||
|
|
cattle |
1.4 |
1.5 |
1.6 |
1.3 |
1.5 |
|
|
pigs |
4.8 |
5.0 |
1.9 |
2.5 |
3.5 |
|
|
laying hens |
34 |
16 |
3 |
15 |
17 |
|
|
broilers |
23 |
38 |
6 |
37 |
25 |
|
Nitrogen transfers (kg N per ha UAA per year)
|
||||||
|
|
animal manure availability |
149 |
148 |
114 |
118 |
134 |
|
|
nitrogen from mineral fertilizer |
81 |
95 |
129 |
62 |
93 |
|
|
crop uptake |
150 |
144 |
146 |
146 |
146 |
|
|
“surplus” |
80 |
99 |
97 |
34 |
81 |
The simultaneous presence of large amounts of animal manure and of pollution does not in itself demonstrate a link of strict causality. Research conducted in Brittany in this respect is contradictory. SRAE (1986; cited by Rainelli, 1991) concluded that the effect on water quality of pig and poultry husbandry in an area of Nord-Finistère is not altogether clear. Contrarily, another study conducted in Finistère concluded that ground water quality was positively associated with density of pigs and poultry (André and Dubois de la Sablonière, 1983; cited by Rainelli, 1991). However, it seems likely that emissions from animal manure are positively correlated to the number of animals per unit of land available for manure application. But even when manure availability matches crop requirements, problems still might exist because of incorrect application, for example by the use of inefficient machinery or application at the wrong time of the year (Brandjes et al, 1995).
Brandjes (op.cit.) calculate how many pigs can be kept per ha of UAA in the case of P equilibrium fertilization. The same can be done for laying hens and broilers, based on a yearly P excretion of a high-productive laying hen of 0.22 kg P*yr-1 and for a high-productive broiler 0.10 kg P*yr-1 (Brandjes et al, 1995). Assuming a low production level for grain with an annual DM production equal to 2 tons*yr-1 with a P-uptake of 6.4 kg P*ha-1*yr-1 and a high production level with an annual DM production of 9 tons*yr-1 with a P-uptake of 28.8 kg P*ha-1*yr-1, then 29 and 131 laying hens, and 64 and 288 broilers can be kept per ha at the low and the high production level, respectively.
Many studies have been conducted to examine the amounts of fossil energy used in agriculture. Despite these studies, current data on energy use in industrial agriculture are conflicting, mainly because of the different methods used by the various researchers to define the system boundaries (Walker, 1984 cited by Barber et al., 1989).
Overall, agriculture is a modest user of fossil energy relative to other economic sectors, accounting for an estimated 3.5% of commercial energy use in developed countries and 4.5% in developing countries (FAO, 1981, cited by Chen, 1990). These estimates take into account energy use in irrigation, pesticide/fertilizer production and machinery production and operation, but not energy use in food processing, storage and transportation. When the last-mentioned are taken into account, along with other food system activities, agriculture’s share of energy consumption increases significantly. For example, Pimentel (1980, cited by Chen, 1990) attributes 17% of US fossil fuel consumption to food system activities, divided roughly equally between food production, processing and preparation.
Southwell & Rothwell (1977) investigated energy inputs for on-farm production of pork, broilers and eggs in Ontario (Canada). In their analysis, they traced all energy inputs back to the original energy resource. For example, the true energy cost of using a cubic metre of natural gas for heating a barn included the direct energy content of the gas, plus the energy used to obtain the gas from the wellhead. The energy cost of the feed is taken as the total energy required to produce and process the ingredients. Thus, the energy cost included the energy needed to cultivate, seed and harvest, and the energy required to produce the chemicals, fertilizers and equipment involved in crop production.
In a study in the Netherlands (Leijen et al., 1993), the energy consumption in pig and poultry production was also calculated starting with the transport of feed ingredients from the border of the country of origin to the Netherlands. Energy needed to grow feedstuffs was not included. In order to make energy cost of feed production more comparable with data from Southwell & Rothwell (op.cit.), we recalculated total energy cost for feed production, including cost for the production of feedstuffs and their transport to the borders of the countries of origin (based on Brand & Melman, 1993). A summary of the data for fossil energy input in the production of pork, broilers and eggs for the Dutch and the Canadian situation is given in Table 3.5. One energy component is not mentioned in Table 3.5: energy needed for manure removal. As far as removal of manure from the farm is concerned, this is only a minor energy consuming activity. Not too much attention should be paid to the absolute values mentioned in the table or to the differences in results between Canadian and Dutch data. These differences are chiefly because of the different assumptions underlying the calculations and the different (e.g. climatic) conditions in the countries involved.
The main conclusion from Table 3.5 is that energy costs for feed is by far the most important energy input in LLM systems. Important criteria that determine energy costs of feed production are as follows:
- Nature of feedstuffs used in concentrates. Some of the feedstuffs used in concentrates might be especially grown for the purpose of pig and poultry feeding, in which case all the energy needed to grow this feedstuff may be assigned to LLM systems. An example is feed grain. In other cases feedstuffs might be by-products from crops that are grown for human food, then only part of the energy needed to grow the crop can be assigned to LLM systems. In most of these cases, Brand & Melman (1993) even set energy costs for production at zero. An example is sunflower extraction. Thus, the energy costs for feed are to a large extent determined by the composition of concentrates. The more these concentrates are composed of feedstuffs which are especially grown for feed, the higher the energy costs.- Transport distances to be covered from feedstuff producing farm to animal farm and means of transport. Energy costs for transport by car (including maintenance, infrastructure and production) range between 2.8 MJ*t-1*km-1 (Brand & Melman, 1993) and 4 MJ*t-1*km-1 (Pimentel & Pimentel, 1979). Transport by ship requires about 0.3 MJ*t-1*km-1. Transport costs may vary considerably among countries, since the extent in which country produced feedstuffs are used varies between countries.
- Energy costs of processing in concentrates. In general, these energy costs are relatively low (0.22 MJ*kg-1) with mixing and milling accounting for about 14% of the energy needed for processing, molassing 50%, compressing 31% and packing 5% (Brand & Melman, 1993). For each feedstuff, the energy costs for processing will vary. Energy costs will particularly increase when drying of the feedstuff is needed. Drying of beet pulp, e.g. costs ca 10.8 MJ*kg-1, illustrating the possible trade-off between the positive aspect of utilizing crop by-products and fossil energy use.
Table 3.5: Energy input for production of pork, broilers and eggs for Canada and the Netherlands.5 Energy input for production of pork, broilers and eggs for Canada and the Netherlands (sources: Southwell & Rothwell, 1977, Leijen et al., 1993 and Brand & Melman, 1993; all data in kJ per kg live weight or eggs)
|
Component |
pork |
poultry meat |
eggs |
|||
|
Can. |
Neth. |
Can. |
Neth. |
Can. |
Neth. |
|
|
Housing |
||||||
|
Fuel, electricity |
2970 |
3056 |
8196 |
3503 |
5438 |
1161 |
|
Building, equipment |
434 |
- |
1049 |
- |
462 |
- |
|
Total housing |
3404 |
3056 |
9245 |
3503 |
5900 |
1161 |
|
Feed |
||||||
|
Transport |
- |
3675 |
- |
2423 |
- |
3611 |
|
Production and processing |
- |
12165 |
- |
12163 |
- |
9311 |
|
Total feed |
20510 |
15840 |
13631 |
14586 |
18942 |
12922 |
|
Total energy input |
23914 |
18896 |
22876 |
18089 |
24842 |
14083 |
|
Feed (% of total) |
86 |
84 |
60 |
81 |
76 |
92 |
Energy output of livestock products comprises both nutritional and non-nutritional outputs. Southwell & Rothwell (1977) calculated the nutritional energy outputs for some animal production systems as the metabolizable energy content of all products, intended for human consumption. Thus, comparisons can be made of output/input ratios for different animal production systems. It then appears that production of meat and eggs is relatively energy intensive, when compared with e.g. milk production. Southwell and Rothwell calculations of output/input ratios for pork, poultry meat and eggs amounted to 0.38, 0.11 and 0.32 respectively, while this ratio was 0.50 for milk production. Note, comparisons among agricultural products on the basis of energy ratios can be quite misleading, since all food products contain many more attributes than just metabolizable energy (Barber et al., 1989). Fluck (1979) calculated energy efficiency ratios as kg of food per MJ of energy input and concluded that this ratio was more meaningful than energy output/input ratios. However, comparing energy output/input ratios within different pork and poultry production systems would still be interesting.
A large proportion of non-nutritional energy output in animal production systems is in the form of manure. Non-nutritional energy output in livestock production was calculated as energy in manure, needed for the production of an equal amount of nutrients in artificial fertilizer. The potential for recovery of this energy has led to a great deal of research in the past 30 years. The major alternatives that have been identified are recycling of manure for use on cropland, extracting energy in the form of methane, processing for protein recovery and recycling into animal feed. Recycling of nutrients on to cropland remains the best alternative for most livestock farms (Barber et al., 1989). In Chapter 4 we will deal with these various options.
Although Cu and Zn are heavy metals, they are also primarily essential minerals for animals. Cadmium (Cd) is nothing but a pollutant of animal feeds, mainly introduced via feed phosphates. In general, Cu levels in the various feed ingredients of concentrates are altogether high enough to meet the animals’ Cu requirements. Nevertheless, it is common practice to add additional Cu to feed rations via mineral mixtures. Zinc (Zn) requirements can to a large extent, but not completely, be covered by only the feed ingredients as such. Thus also for Zn it is common practice to add additional Zn via mineral mixtures. This adding of additional Cu and Zn to feeds generally results in a large oversupply. Reasons for this oversupply are (Jongbloed et al., 1985):
- positive influence by Cu on growth performance of pigs, particularly at sub-optimal management levels. However, its physiological effect is not exactly known and therefore it is not known to what extent Cu levels could be reduced without affecting the growth performance of pigs;- minimum requirements for Cu and Zn can never be exactly determined, because they strongly interact with other nutrients in feeds (e.g. Ca and phytine), causing fluctuations in Cu and Zn availability.
The addition of Cu and Zn to animal feeds in the European Union results in roughly a factor 2 above the requirements of pigs and poultry. Within the European Union, Cu levels in pig rations have gradually been reduced during the late seventies and early eighties: pig starter rations from 200 to 175 mg*kg-1 and fattening rations from 200 to 35 mg*kg-1 in order to prevent Cu accumulation in soils (Beukeboom et al., 1991). In both pig and poultry feed rations the Zn content amounts to 90 mg*kg-1. Data on the heavy metal content in feed used in other regions of the world are scarce. For the Canadian pig ration presented in Annex 4, it is known that the Cu and Zn content amounted to 140 and 145 mg*kg-1 respectively, thus both considerably higher than present EU levels.
During the eighties, the Cd content of feed rations has gradually been reduced in the Netherlands. Average Cd content in the second half of the eighties amounted to 0.07 mg*kg-1 compared to 0.14 in the early eighties. This reduction is mainly due to the reduced use of feed phosphates, accompanied by lower Cd levels in these feed phosphates.
Accumulation of heavy metals in soils may be expected to occur, when their supply via animal manure exceeds crop uptake. This might occur when pig and poultry manure is applied at high rates for a long period of time. In Table 3.6 the supply of Cd, Cu and Zn to soils is given for some common mineral and organic fertilizers, per kg N and P applied. Table 3.6 refers to the situation in the mid-eighties in the Netherlands. It must be emphasized that little is known about heavy metal contents of animal and mineral fertilizers. Data on heavy metal content within comparable products vary strongly. This is due to (Heidemij, undated):
- the diversity in production processes;
- the diversity and variety of feedstuffs and other compounds used in concentrates; and
- the analytical methods applied to quantify heavy metal contents of products.
Nevertheless, from Table 3.6 it can be concluded that animal manure contains high levels of Zn and Cu per kg of N or P applied, compared to mineral fertilizers. The opposite is true for Cd.
Pig manure contains on average the largest amounts of Cu and Zn per kg of N and P2O5 applied. Brandjes et al. (1995) calculated the supply of Cu, Zn and Cd via pig manure for a maize crop in the Netherlands under P equilibrium fertilization, and concluded that for pig manure problems from the accumulation of Cd and Zn are not very likely. The opposite was true for Cu: supply of Cu would exceed uptake by a maize crop more than 5 times.
Table 3.6: Supply of heavy metals (Cd, Cu, Zn) in mg per kg N and P applied to soils for some common artificial fertilizers and animal manure.6 Supply of heavy metals (Cd, Cu, Zn) in mg per kg N and P applied to soils for some common artificial fertilizers and animal manure (Heidemij, undated)
|
|
Cd |
Cu |
Zn |
|||
|
N |
P |
N |
P |
N |
P |
|
|
mineral fertilizers1 |
|
|
|
|
|
|
|
superphosphate |
- |
183.2 |
- |
172.2 |
- |
3121 |
|
triplesuperphosphate |
- |
179.3 |
- |
159.6 |
- |
3284 |
|
NP 26-14 |
34.2 |
145.4 |
45.6 |
194.0 |
380 |
1617 |
|
NPK 12-10-18 |
33.0 |
90.7 |
33.0 |
90.7 |
562 |
1543 |
|
organic manures |
|
|
|
|
|
|
|
poultry slurry |
4.7 |
14.4 |
1321 |
4058 |
6887 |
21162 |
|
solid poultry manure |
14.8 |
29.1 |
2346 |
4612 |
8436 |
16589 |
|
solid broiler manure |
15.8 |
39.2 |
2615 |
6488 |
8385 |
20800 |
|
porker slurry |
4.6 |
17.6 |
7846 |
29946 |
7846 |
29946 |
|
cattle slurry |
6.1 |
34.4 |
1429 |
8015 |
5102 |
28625 |
When the supply of heavy metals to soils exceeds crop uptake, the heavy metal content of soils will increase, which in the long term may threaten the multi-functionality of soils. Depending on the crop, crop uptake on soils with high heavy metal levels may become so high that consumption of the crop (by animals or humans) entails health risks.
Methane is emitted from two sources in LLM systems: from digestive processes in animals and from anaerobic decomposition processes of organic matter in manure. In LLM systems, the latter source is by far the most important.
Methane emissions from anaerobic decomposition processes
Safley et al. (1992) give estimates for methane emissions from pig and poultry manure per country. These estimates are largely based on animal populations present in the second half of the eighties. Some background on their calculation method is given below.
Actual methane production can be defined as the quantity of methane produced per kilogram of volatile solids (VS) in manure, for a given set of manure management practices and climatic conditions:
actual methane emission = B0 * CAF * MCFmms (in m3 CH4*kg-1 VS)
|
where: |
B0 = |
maximum methane producing capacity of the manure, determined
by animal type and diet (in m3 CH4*kg-1
VS); |
|
|
CAF = |
climate adjustment factor, that represents the extent to which
B0 is realized under a given set of climatic conditions (e.g.
temperature and rainfall). 0£CAF£1; |
|
|
MCFmms= |
methane conversion factor that represents the extent to which
B0 is realized for a given animal manure management system. 0£MCFmms£1. |
For a given animal type, B0 is determined by the energy content and digestibility of feeds. The higher the energy content and digestibility, the higher the methane producing capacity. (Animals fed a high energy diet, produce a highly biodegradable waste, containing a large fraction of readily available organic material.)
Annual methane emissions are estimated after determining values for the parameters described above and after calculation of total production in VS by pigs and poultry per country. Emissions from LLM systems can then be estimated by summation of the emissions per country to the level per region, followed by multiplication by the LLM factor for each region. For example: Safley et al. (op.cit.) give annual methane emissions from pig manure for all Asian countries in metric tons*yr-1. Summation of these methane emissions results in total emission from pig manure in Asia. An estimate for pigs in LLM systems can be derived by multiplication with the conversion factor for LLM systems for Asia (0.29; see Table 2.1). Applying this method to all regions and animal types, results in methane emissions from manure in LLM systems as given in Table 3.7.
The method applied contains some inaccuracies:
a) Methane emissions are uncertain, because of limited availability of data on animal numbers, feeds used, types of animal manure management systems, values for the parameters, etc. This is especially true for developing countries.b) As stated, methane emissions are based on animal populations present in the second half of the eighties, and thus are the emissions given for LLM systems. Since then, however, animal numbers in general, and more significantly in LLM systems, have been increasing.
c) Estimates are given for the large majority of the countries of the world, but not for all. Safley et al. consider some 115 countries, whereas this study takes 150 countries into account. The countries not considered are all of little importance to LLM systems, excepting Taiwan.
d) The estimates given per country, are based on average values for B0 and MCFmms. However, LLM systems have, compared to other pig and poultry systems, relatively higher B0 and MCFmms values per animal. (B0 will be higher, because feeds used in LLM systems will on average have a higher energy content, whereas MCFmms values will be higher, because anaerobic conditions are most likely to occur in locations where large numbers of animals are housed in confinement.)
Table 3.7: Estimated methane emission from pig and poultry manure in LLM systems.7 Estimated methane emission from pig and poultry manure in LLM systems (in metric tons*yr-1)
|
region |
poultry manure |
pig manure |
total |
|
SSA |
23,419 |
4703 |
28,122 |
|
ASIA |
261,229 |
466,109 |
727,338 |
|
CSA |
146,330 |
89,539 |
235,869 |
|
WANA |
36,365 |
32 |
36,397 |
|
OECD |
420,663 |
1,587,359 |
2,008,022 |
|
CIS + EE |
175,241 |
329,658 |
504,899 |
|
OTHERS |
5,847 |
2,272 |
8,119 |
|
WORLD |
1,130,242 |
2,292,795 |
3,423,037 |
The calculation method applied above suggests that the methane emission per animal in LLM systems will be relatively higher than in other pork and poultry production systems. However, the picture is likely to be completely different when methane emission is expressed per kg product. More accurate information may be found in the report on methane.
Methane emission from digestive processes in animals
Data on methane emission from digestive processes in poultry have not been found. According to Crutzen et al. (1986), methane emission from pigs in developed countries amounts to 1.5 kg*pig-1*yr-1 and in developing countries to 1.0 kg*pig-1*yr-1. Thus, when the average number of pigs present at a certain time of the year is known for both types of country, the methane emission from digestive processes in pigs can be calculated. The number of sows and porkers annually produced in LLM systems is calculated in Annex 4. Sows are assumed to be present year-round. In 1991, there were approximately 9,334,155 sows in developing countries and some 13,230,551 in developed countries. The number of porkers annually slaughtered in developing countries amounted to 131,550,991 in 1991. Assuming an average age at slaughter to be 175 days, the average number of porkers present in developing countries at a certain time of the year can be calculated as (175/365) * 131,550,991 = 63,072,392 heads. The same calculation for developed countries results in 105,816,626 porkers on average. Total CH4 emission from digestive processes in pigs in LLM systems can then be calculated as 250,978 ton*yr-1.
The total world methane emission is estimated at 540,000,000 metric tons*yr-1, ranging between 440,000,000 and 640,000,000. The contribution of methane from decomposition of total animal manure amounts to 28,000,000 metric tons*yr-1, equal to 5.2% of total emissions. The contribution of LLM systems is only 0.63%. Methane emission from digestive processes in LLM systems is insignificant as well. Livestock accounts for 15-20% of global methane emissions, which contributes 3% to global warming (Durning & Brough, 1992; cited by Tolba et al., 1992), while methane contributes 18% to overall global warming (Leng, 1993).
Following Verheyen et al. (1995), slaughterhouses can be classified on the basis of their final products. A slaughter and packing house that processes meat to products, such as canned, smoked and cured meat, produces significantly more waste than a simple slaughterhouse that is only producing carcasses. Another relevant distinction is that between OECD-countries and other countries. In OECD countries, where environmental concern has grown considerably, care is taken to use by-products, blood and offal as much as possible and treat the waste water before disposal. In many other countries blood is washed away, offal is wasted (washed or dumped) resulting in high water pollution levels.
The key indicator chosen by Verheyen et al. (1995) to quantify the amount of waste produced in slaughterhouses is the amount of Live weight killed (LWK). In fact this is an indirect indicator and may be regarded as an integrated indicator for the more direct waste (like e.g. the amount of solid waste, BOD, N and P).
Based on the production values given in Tables 2.1 and 2.2, it is estimated that the production in LLM systems is around 40 * 106 tons LWK pigs (assuming dressed carcass weight as 70% of LWK) and 49 * 106 ton LWK poultry (assuming “ready-to-cook-weight” as 65% of LWK).
Typical values for BOD, N and P per kg LWK, given by Verheyen et al. (1995) have been used as production is fairly evenly divided between OECD countries and other countries. In Verheyen et al. (1995) only scanty information is presented on solid waste production. The estimates in Table 3.8 are based on the following assumptions:
- production in OECD countries: negligible amounts of solid waste (10 kg and 0 kg for pig and poultry respectively);- production in other countries: 50% of “1 minus dressing” “1 minus ready-to-cook” percentage is assumed to be dumped.
The resulting total emissions are given in Table 3.8. Total produced waste water can be considered problematic, leading to severe water pollution, because animal processing in LLM system is considered to be completely centralized, assuming the number of broilers sold alive are negligible.
Table 3.8: Waste production by animal processing in LLM systems.8 Waste production by animal processing in LLM systems.
|
|
pork |
poultry meat |
|
Solid waste (kg*ton-1 LWK) |
76.8 |
73.5 |
|
Solid waste - total (* 106kg) |
3071 |
3600 |
|
BOD (kg*ton-1 LWK) |
5 |
6.8 |
|
BOD - total (* 106kg) |
200 |
334 |
|
N (kg*ton-1 LWK) |
0.68 |
n.a. |
|
N - total (* 106kg) |
27 |
|
|
P - (kg*ton-1 LWK) |
0.05 |
n.a. |
|
P - total (* 106kg) |
2 |
|
Agriculture produces enough food calories to meet the world food requirements, as determined by the UN nutritional standards (in fact, even some 20% above these world food requirements). Calculations even indicate that at global level potential food production in 2040 will exceed predicted food demand, even if highest food demand is assumed (high population growth and an affluent diet). Regional deficiencies are likely to occur mainly in Asia if these highest food demand projections materialize, but will disappear if population growth is more modest (Penning de Vries et al., 1995).
However, large surpluses and deficits exist at regional, national and sub-national levels, since food production, purchasing power and consumption are not distributed evenly among the world population. For example, in the mid to late eighties, as many as 1.5 billion people lived in countries where dietary energy supplies were inadequate to meet national nutritional needs, and some 350-500 million people lived in households too poor to obtain enough calories for minimal adult activity and the healthy growth of children (Chen, 1990).
Competition between food and feed occurs along two pathways: directly through competition between animals and man for food that is suitable for both, and indirectly through competition for land on which feed or food can be produced. In this section the main emphasis is on the direct form of competition.
LLM systems account for 32% of total concentrates fed to livestock (Hendy et al., 1995). Estimates for the percentage of the world cereal harvest fed to animals vary somewhat. Anonymous (1994b) gives an estimate of 37% for 1992, whereas Hendy et al. mention 44% for 1993. Whatever the exact estimate, it implies that at global level there is certainly competition between food and feed use of cereals, and this may affect cereal prices. However, the nature of the food - feed competition is quite complex, and for developing countries may not be as significant as it might appear from global feed use. Of the 637 million tons of cereals fed on average to livestock over the period 1988-1990, only about 24% was fed to livestock in developing countries. This 24% was distributed over developing countries as follows: East Asia 47.4%, South Asia 1.9%, North Africa and the Middle East 20.5%, Sub-Sahara Africa 1.2% and Central and South America 29% (Hendy et al., 1995).
The use of cereals for feed in developing countries increased by about 8% per year in the past decade, in contrast to only 1% in developed countries. This increase was particularly dominated by growth in feed use in middle-income countries and the newly industrialized countries in Asia and Latin America, as well as in the oil exporting countries. The rapid growth of the poultry industry is a major factor behind the increased feed demand in these countries. This is related to a growing demand for livestock products in the course of development. In earlier stages of development, livestock are fed mainly waste and by-products, the supply of which in livestock production is inelastic. Therefore, as demand for livestock products grows, so does feeding with cereals suitable for direct human consumption. Data for e.g. Taiwan are illustrative. In 1961 feed use of cereals was less than 1% of total use; by 1981 it was 60% (Mellor & Johnston, 1987). This may lead to rising real prices of food when the nature of competition between food and feed utilization may result in an adverse effect on food consumption of the poor, especially in countries whose growth path is combined with a skewed income distribution (von Braun & Kennedy, 1987).
Similar developments like that in Taiwan are expected to occur in China in the near future. This raises the question whether China can remain a net exporter of feedstuffs. According to Simpson et al. (1994) this is the case. They state that China can meet both its human food and animal feed requirements in the near future, even if the economy is sluggish.
1 Compared to 63% in European countries (Alexandratos, 1990).
Competition between food and feed could be mitigated by the incorporation of more by-products and offal in feed rations. In fact, the utilization of by-products and offal by LLM systems is a positive interaction with the environment: all kinds of waste unsuitable for human consumption are not disposed of, but instead utilized to produce food with high nutritive value (i.e. meat and eggs). No data have been found that allow us to estimate the extent to which by-products and offal are currently used in feed rations in LLM systems. In Annex 4 some common feed rations used in Canada, the Netherlands and tropical regions were already presented in another context. The Canadian ration may be assumed to be representative for North America, and the Dutch ration for West European countries (with an additional note that in the Netherlands tapioca is used instead of cereals as is done in most other European countries). However, it is far from clear to what extent the tropical rations are representative for the tropical regions. The observed lack of data on feed use is in line with observations on feed use made by Alexandratos (1990) and Sere & Steinfeld (1995). A system-wide quantification of the use of by-products and offal is therefore not feasible. However, in general it can be stated that the more sophisticated an animal production system (in terms of breeds used, housing and equipment, etc.), the higher the quality of the feed rations (where quality is defined in terms of digestible energy and protein content and amino acid pattern). Feedstuffs of high quality are usually cereals and protein-rich animal products, whereas most by-products of food industries show lower digestibilities (Schutte & Tamminga, 1992)1. So, compared with other pork and poultry production systems, in LLM system feeding rations contain relatively more feedstuffs that are also suitable for human consumption. However, alternative feed rations for poultry are possible as indicated by El Boushy and van der Poel (1994): conventional poultry rations contain up to 60% grain and 15% soya. Roughly half of this ration could be replaced by carbohydrate wastes, such as potato waste, date pits, tomato waste, or protein wastes, such as by-products from slaughterhouses and products from waste-water treatment plants.
1 In the Netherlands this feature of by-products seems to have led already to substitution of the by-product vinasse in cattle rations with compounds of higher nutritive value, in order to meet governmental legislation on maximum P fertilization (pers. comm. van der Meer, 1995).
In the context of competition between food and feed, Smith (1990) considers the further development and expansion of intensive poultry production only desirable if one or more of the following conditions prevail:
- the country produces a large surplus of plant foodstuffs over and above the needs of the human population;- the country has a large manufacturing base that generates sufficient foreign exchange to purchase animal feedstuffs;
- the country has an exportable commodity that can be exchanged for animal feedstuffs.
If none of these conditions is met, it would be better to pursue a policy of encouraging scavenger poultry production. The reason is that in countries where food is in short supply, the effect of intensive poultry keeping is the transformation of food that poor people can afford into a much smaller quantity of food that only rich people can afford but almost certainly do not need.
Serious concern exists about contaminations in livestock products, particularly those originating from intensive systems such as LLM systems, and their negative direct and indirect effects on human health. Different types of problems may be relevant, e.g. antibiotic resistant pathogens, heavy metals, chemicals, hormones and mycotoxins, each with its own problems. The extensive use of non-therapeutic antibiotics has come under criticism, because of increasing antibiotic resistance in bacteria which becomes a danger to human health. Most antibiotics are excreted in a relatively short time, and no residues will appear in animal products if recommended withdrawal times are complied with (Hapke & Grahwit, 1987). The main concern is related to the relative high incidence in pig meat of sulphonamides and, to a lesser extent, tetracyclines. Violations of safety levels remain well below 1% in the USA and the UK, but major efforts are being made to further reduce the incidence (Ritchie, 1995; Livesey, 1994).
There is evidence that bacteria that are pathogenic to animals and man can acquire multiple antibiotic resistance in the gut of farm animals and can be transmitted to man via food or direct contact by farm workers (Willinger, 1987). Moreover, non-pathogenic E.coli can act as a source of resistance to pathogenic E.coli and salmonella, though in practice transfers will be rare (Strauch & Ballarini, 1993). The extent to which antibiotic resistant pathogens are the result of extensive non-therapeutic use of antibiotics, is scarcely known, because of difficulties in tracing the origins of a resistant strain. The resistance can also be due to therapeutic use, both in animals and in men. There are only a few proven cases of antibiotic resistant bacteria in humans originating from non-therapeutic antibiotic use in animal husbandry (Willinger, 1987).
Because of the potential problems with antibiotic resistant pathogens, only a few antibiotics are allowed for non-therapeutic use in animal feeds, but thus far this has barely resulted in a reduction of the prevalence of antibiotic resistant pathogens. This is probably so because no measures have been taken simultaneously in respect to human use, thus still providing a major input to the pool of bacterial resistance (Walton, 1986).
Contamination of pig and poultry products with pathogens is of major concern, both for animal and human health. Particularly salmonellosis has been steadily spreading in the past decades, partly due to fish protein contaminated with new serotypes, as a result of a scarcity of salmonella-free animal protein feedstuffs (Walton, 1986). Once established in the environment, the incidence of infected wild birds is high e.g. around poultry plants (Davies & Wray, 1994) and salmonella is difficult to eradicate. In some areas more than 1/3 of the pigs and 1/2 of the broilers slaughtered are infected (Strauch & Ballarini, 1993). Eggs are also often infected, which is more problematic as eggs are regularly used in human food without heat treatment.
Organo-chlorines such as DDT and lindane of serious public concern, as these compounds are highly persistent (see Table 3.9). The presence of organo-chlorines in animal fat tissues, where they are mainly deposited, is not only the result of their use against ectoparasites in animal husbandry, but also of their presence in animal feed. In the latter case, animals are intermediate victims of pesticide use in grain production. As with heavy metals, concentrations of organo-chlorines in livestock products may be higher than in the feed ration, because several kilograms of feed are used to produce one kilogram of meat.
In most developed countries, levels are well below safety levels as organo-chlorines are replaced by other, less problematic ectoparasite drugs, and also in grain production they are hardly used any more. In other countries they are still used both in livestock and crop production. Then high levels of organo-chlorines may occur in livestock products. For example, in India, DDT levels up to 7.2 ppm in animal fat have been measured, compared with levels up to 175 ppm in pulses (Gupta, 1993).
Several types of hormones are used in LLM systems (legally, illegally or uncontrolled) to increase weight gain, feed conversion ratios and/or to change meat composition (less fat) such as:
- anabolic steroids (e.g. testosterone, progesterone, zeranol),
- beta-agonists (e.g. salbutamol),
- corticoids (e.g. cortisone),
- somatotropines (e.g. PST).
|
DDT |
0.02 - 0.25 |
|
DDE 1 |
0.02 - 0.1 |
|
DDD 1 |
0.01 - 0.06 |
|
Lindane |
0.01 - 1.0 |
|
HCB |
0.01 - 3.3 |
|
Dieldrin |
0.005 - 0.02 |
|
PCB 2 |
0.01 - 0.41 |
1 Metabolites of DDT.2 Polycyclic biphenyls are no pesticides but have a toxicological relevance identical to organo-chlorines
Source: Hapke & Grahwit, 1987
Each hormone has different characteristics: e.g. beta-agonists have a very short half-life and may cause allergic reactions and palpitations in humans, while stilbenes (e.g. DES) are still detectable several weeks after application and have proven to be carcinogenic (Hapke & Grahwit, 1987). Moreover, only a few countries have monitoring systems and even these systems are frequently criticised for being insufficient (e.g. Lefferts, 1995). Therefore, generalization is impossible.
Due to the short half-life of most hormones (Ritchie, 1995; Hapke & Grahwit, 1987), low residue levels are expected in meat products. For example, in the USA, no sample analysed exceeded tolerance rates (Ritchie, 1995). In the EU no hormones are allowed, though a scientific basis does not exist for the ban on most steroid hormones (Pratt, 1994; Vandemeulebroucke, 1993). Still in some countries up to 10% of the meat samples analysed did contain hormones (mainly beta-agonists and anabolics; Vandemeulebroucke, 1993). The illegal use is caused by the fact that several hormones not permitted for regular application in fattening, are allowed for medical or veterinary treatment of humans or animals (NRC, 1987; Vandemeulebroucke, 1993). In several other countries neither regulations nor monitoring systems are present. Therefore, the extent of hormone utilization is unclear, but it may be assumed that hormones are widely used due to the high net profits involved (Ritchie, 1995).
Heavy metal contamination of livestock products, mainly kidneys and liver, are rare (Craigmill, 1995; Livesey, 1994). If incidents do occur (mainly concerning lead and arsenium), they are usually related to high soil intake, which is uncommon in landless systems, and contamination of feed during transport (Livesey, 1994). Regular feed additions of Cu, Zn and Cd (the latter originating from P additions) do not add to these problems.
Mycotoxic problems, such as aflatoxin, are not a major public concern in contrast to that of scientists (Craigmill, 1995). The biological effects of mycotoxins include liver damage and nephrotoxic, neurotoxic, mutagenic, carcinogenic and teratogenic effects (El-Darawany & Marai, 1994; Gupta, 1993). Their impact on livestock is of prime importance; humans can be affected too, but it is highly unlikely that livestock products contribute to this (Livesey, 1994). Mycotoxic problems are not considered as problematic in developed countries (Strauch & Ballarini, 1993), mainly due to rigorous screening of feed samples by feed mills, though incidents with high animal losses do occur (Gupta, 1993). In developing countries, mycotoxic problems are likely to be much higher as storage conditions are much more problematic (mould), while feed monitoring often hardly exists (Gupta, 1993).
Note, the data mentioned do not specifically relate to LLM systems, such a differentiation is not used in monitoring programmes. Moreover, most aspects are not specific for landless systems or even livestock systems, e.g.:
- Salmonella and E. coli are often of greater concern in extensive livestock systems than in intensive systems: mortality rates of young stock in extensive systems of up to 30% are common, mainly due to these pathogens (Brander, 1986);- improper antibiotic use is still a major problem in situations where education standards are low, veterinarians are scarce and antibiotic products freely available in the markets;
- heavy metal contamination is more common in wild animals and fish than in domestic animals (Hapke & Grahwit, 1987), probably related to higher total feed quantities consumed by these animals as they become older.
Problems relevant to landless systems are related to incidental contamination of feed during transport and storage, and to the complexity of feed chains of landless systems: several feed components originate from various, sometimes unknown, sources (Livesey, 1994). Particularly the latter problem is of major concern: monitoring systems are in general better developed in intensive systems, but screening for every possible contamination is highly labourious and costly.
The incidence of salmonellosis is of particular concern in LLM systems, mainly due to the introduction of new serotypes by feed originating from other countries and because the large herds common in LLM systems, often have a reduced immune status while disease control is more difficult (Seabrook, 1986; Walton, 1986)
Breeds and native populations are the reservoirs of genetic diversity within species. Although livestock and poultry species are not in danger of extinction, a substantial number of breeds within those species are declining in population and size. Losses generally occur because the breeds no longer compete effectively within their respective production-market environmental niche. The extent to which these losses will actually reduce genetic variation within species is not known nor easily measured (Mason & Crawford, 1993).
Across much of the world, the fifties and sixties was a period of breed consolidation and the emergence of “global” breeds such as Landrace, Large White (pigs) and Leghorn (poultry). Many local breeds declined in popularity, to be absorbed or replaced by international breeds (Philipson & Wilson, 1994). Enormous investments in breeding technology have been combined with aggressive marketing of the resulting products through sales of semen and embryos and the setting-up of a vertically-integrated agribusiness. Whole populations of animals have been replaced in the pursuit of current productivity, but short-term economic gains may well have masked long-term biological losses. According to Philipson & Wilson (1994), evidence is clear for pigs and poultry: genetic resources for these animals in much of the developed world have been ravaged in the search for and the promotion of synthetic high yielding strains.
Traditional indigenous breeds, particularly in developing countries, are generally considered to be in great danger of genetic loss. In the tropics, temperate breeds usually cannot be introduced as pure-bred animals without also introducing high levels of feeding, special management, investments and risks. Small farmers often cannot afford the cost of the high-maintenance breeds that are being introduced. However, these breeds are commonly crossbred with local animals to combine adaptation and disease resistance with higher production. Although the traditional indigenous breeds are needed initially to produce crossbreeds, their critical role in maintaining self-perpetuating breeding programmes is often not recognized. Farmers may be reluctant to keep the indigenous breeds if they are less profitable than crossbreeds. As a result, indigenous breeds loose their genetic identity or disappear (Anonymous, 1993c)
From the above, it is clear that in LLM systems only a limited number of animal breeds are used: those that are biologically and economically suitable for these systems. In general, these breeds have a narrow genetic background, often originating from OECD countries. Considering the rapid expansion of LLM systems in most regions of the world, they may contribute substantially to genetic erosion. The key question with respect to the contribution of LLM systems is whether these systems compete with the more traditional pork and poultry production systems using the traditional breeds for market shares, or whether market shares are completely supplementary. Literature dealing with this question is contradictory. For example, Verhulst (1993) states that where the different systems happily co-exist there is no conflict between intensive, semi-intensive and extensive pig farming in developing countries. The traditional sector mainly supplies the rural population and the intensive sector the urban centres under rapid expansion. On the other hand, Sere & Steinfeld (1995) state that the LLM systems typically compete with traditional land-based production for market shares in the urban markets. They therefore conclude that the expansion of LLM systems is clearly linked with the extinction of traditional breeds.
It can be expected that the degree of competition between landless and land-based systems varies among countries and in time. For instance, in China, the many local breeds are not yet in danger, but in Taiwan local breeds have almost entirely been replaced by improved breeds from the USA and Europe to suit the intensive husbandry systems that have been developed (Mason & Crawford, 1993).
Pressure being put on local breeds comes from the continuing rapid changes to a more world and market-oriented agricultural economy, coupled with greater access to exotic germplasm, improved technology for livestock propagation, changes in market preferences of urban consumers and shortages of government funds. The competitive pressure from imported international breeds will almost certainly continue to increase, with associated losses in economic viability of many local breeds (Philipson & Wilson, 1994).
Issues surrounding the conservation of animal genetic resources have been discussed for more than 30 years. Conclusions generally have been similar (Anonymous, 1993c):
- diversity in livestock breeds is increasingly at risk;
- valid reasons exist to conserve diversity;
- organized preservation and management activities are highly desirable.
Increasing public concern is associated with LLM systems, like overconsumption of animal products and animal welfare, which may affect production structures in LLM systems significantly, particularly in OECD countries.
Public concern about animal welfare problems in LLM systems is mainly focused on issues as crowding, restriction of freedom of movement, excesses like cannibalism (in growing pigs and laying hens) and “death growers” (broilers), though transport of life animals and slaughter conditions also receive attention. Most of these problems are due to the large increase in farm scale, to the exclusive focus on high production levels and to certain housing systems, e.g. young pigs on slatted floors and laying hens in cages, though the importance of stockmanship is not to be underestimated, particularly in intensive, highly man-controlled systems (Seabrook, 1986; English & MacDonald, 1986; Wiepkema, 1988). Possible changes include a ban on certain housing systems (e.g. EU policies for caged laying hens), larger areas per animal, inclusion of some roughage in pig rations to reduce cannibalism (see Close, 1991, for possibilities and drawbacks), offering straw bedding to pigs or free range to completely confined animals.
Improving animal welfare implies a clear trade-off with costs of production and thus income. While alternative, more animal friendly husbandry systems are available, they have hardly been implemented thus far as increased costs are not covered by higher product prices (English & MacDonald, 1986). In some countries trademarks are introduced, offering consumers the possibility to choose products from more animal-friendly systems. In most cases, however, their market shares remain low.
As far as animal welfare is concerned, no husbandry system is perfect, e.g. more extensive systems are often associated with higher mortality rates, thus trade-offs even exist among different aspects of animal welfare. Trade-offs with environmental issues are also likely, for example:
- roughage feeding to monogastrics will result in higher nutrient excretions per animal;
- larger areas per animal and especially free range opportunities result in higher N losses, mainly in the form of NH3 volatilization.
LLM systems are closely related to increased livestock product consumption, as both are significantly related to income. Many human health problems are claimed to be partially caused by high consumption of livestock products (Durning & Brough, 1991; Rifkin, 1992), mainly due to a related high consumption of saturated fats (causing cardiovascular diseases and cancer) and protein (accelerating age-related decline in renal function). WHO (1990) gives an upper limit of 130 g meat*adult-1*d-1, which is lower than present consumption in many, particularly in developed countries, while there are no known advantages of these high levels of livestock product consumption. These health issues are heavily debated, both the importance of saturated fat and protein and the importance of overconsumption of livestock products. This is not the place to expand on this issue. One aspect of these high consumption rates, however, has some environmental impact: it results in high excretion of N by humans, which has a major impact on water quality of surface waters. In a study of the pollution of the Danube river basin, e.g., it was estimated that total N load of the Danube (approximately 700 ktons N*yr-1) could be reduced by approximately 47 ktons if livestock product consumption would be reduced to recommended WHO-levels (Anonymous, 1994a).
