Chapter 1
NUTRIENTS IN LIVESTOCK WASTES

1.0 GENERAL

Animal wastes represent a vast reservoir of cheap nutrients, particularly for ruminants. In most countries, waste, particularly from poultry, is easily collected, as it is concentrated in small areas, and its cost, as a raw material for feed, is generally the cost of transport alone. The only expensive item may be processing, but this cost is relatively small and is recoverable from the profit arising out of the low original cost. Feed costs for dairy or beef cattle usually represent 50–80% of the total production costs; this can be reduced to 20–40% by utilizing these new feed resources as donors of protein, minerals and other nutrients.

Table 5 shows the levels of some important nutrients that can be obtained from animal wastes.

Table 5
ESTIMATED ANNUAL PRODUCTION OF NUTRIENTS
IN VARIOUS ANIMAL WASTES (on DM)

Sources:¹ Yeck et al., 1975; Smith, 1973;
² Müller, 1974–1975.
^a 4.5 batches per year;
^b 2 batches per year;
^c losses of N are high due to NH₃ displacement;
^d much depends upon the quantity and the nature of bedding used;
^e 500 kg live weight, 15 litres milk. Includes only collectable waste from confined housing.

The chemical composition and thus the nutritive value of wastes depend upon:

• species and classes of animals;
• production capacity, nutrient intake, digestion and absorption;
• feeding management;
• feed wastage (particularly in poultry and pigs);
• plane of nutrition and composition of diets;
• waste management and disposal systems;
• bedding and other added materials;
• environmental factors.

A significant difference exists, however, between fresh manure and manure collected for feeding after processing and storage. Change et al. (1975) found that within 3½ hours from the time of collection the NH₃ content in layer manure increased more than sixfold, indicating the speed of uric acid breakdown.

The nutritive value of excreta is also heavily influenced by the level and nature of structural carbohydrates and other indigestibles (silica) in the ration of animals whose wastes are collected. This was convincingly demonstrated (see Table 6), by US studies (Smith et al., 1970; Smith et al., 1971; Smith, 1973; Goering and Van Soest, 1970; etc.).

Table 6
ANIMAL WASTES: STRUCTURAL CARBOHYDRATES AND
OTHER CRITICAL NUTRIENTS (Percent DM)

The table combines results of different experiments.

Source: Smith, 1973.

Faeces high in neutral detergent soubles are well digested by ruminants (as well as by monogastric species) because this fraction of excreta is primarily of metabolic origin (Smith, 1973). On the other hand, faeces high in cell walls have low nutritive value.

The comparison further indicates that poultry excreta are a much more valuable source of digestible nutrients than ruminant faeces, subject however to the type of ration and, in the case of ruminants, to the forage/feed concentrate ratio. The most valuable constituent of animal wastes is the nitrogenous fraction represented by protein and non-protein nitrogen (NPN). In poultry, because ornithine synthesis does not occur, the main route of N excretion is via uric acid.

The NPN fraction of poultry excreta consists of purines, uric acid and allantoin, all utilizable by the rumen micro-organisms for protein synthesis. The enzymatic pathways of allantoin degradation is as follows (Belasco, 1954):

Allantoin → Allantoic Acid → Urea + Glyoxal → Ammonia

Ammonia as a splitting product of urea can be utilized by rumen micro-organisms in the same manner as urea. Uric acid is better utilized by ruminants than urea, since it is much less soluble in water. The content of uric acid in the urine of poultry is as high as 28 to 55%, but because chicken urine and faeces have the same excretion route, the total content of uric acid is lower. Much however depends upon classes of poultry, levels of nutrition and degree of decomposition of poultry manure. The true protein fraction and its amino acids in animal wastes vary considerably with species and classes of livestock. The highest true protein level is derived from broiler waste, as indicated from the breakdown of nitrogen fractions in broiler litters based on two types of bedding (Bhattacharya and Fontenot, 1965):

The distribution of nitrogen in the excreta of individual animal species is shown in Table 7.

Table 7
DISTRIBUTION OF NITROGEN IN FAECES AND URINE

Source: Smith et al., 1973.

Animal wastes, with the exception of broiler waste, are relatively poor in feed energy. Caloric values of broiler litter for ruminants as reported by several authors are given below:

These caloric values indicate that broiler waste is a quite valuable source of energy for ruminant diets.

The caloric value of dried layer waste is much lower:

The calculated mean energy values of animal wastes for ruminants, estimated in Table 8, indicate that only broiler manure and broiler litter exhibit a TDN value comparable to conventional feed ingredients (Müller, 1975e). The other livestock wastes are low in feed energy, at levels comparable to crop residues.

Table 8
ANIMAL WASTES: MEAN CATTLE FEED ENERGY VALUES¹
(on DM)

¹ in relation to the TDN content at maintenance in take;
² fed 60% concentrate;
³ fed 80% concentrate;
⁴ fed 100% concentrate.
Source: Müller, 1975e.

Mineral feedstuffs, particularly phosphates, have become very expensive, and the incorporation of poultry or pig waste can often reduce the cost of supplementing these minerals in ruminant rations.

Poultry waste and pig waste, as shown in Table 9, are rich in calcium and phosphorus and (with the exception of layer manure) display a very favourable ratio for the requirements of ruminants. Ruminant rations incorporating 15% broiler or pig waste are usually sufficient in Ca and P. Only when layer waste is used may it become necessary to offset phosphorus imbalance.

Table 9
ANIMAL WASTES: MEAN CALCIUM AND PHOSPHORUS CONTENT
(on DM)

Sources:¹ Müller, 1974–75.
² Pearce, 1977.

1.1 POULTRY-HOUSE LITTER

From the biological point of view, deep litter is a biotic community of diverse micro-organisms inhabiting a common biotop, in which a bacterial flora prevails during the early stages. Under the influence of an intensive bacterial microflora, the biochemical activity and temperature of deep litter gradually increase, retarding the development of bacteria so that in the later phases the activity of lower fungi is dominant (Müller et al., 1959). Much however depends upon moisture content and feed wastage as basic factors in facilitating the microbial breakdown of bedding material and droppings and establishing the biocoenosis.

Micro-organisms grow gradually into the litter biotop which is specifically suited to them; they change with the hatitat and help maintain the proper ecological balance by an underlying principle of adaptation, diversity and persistence.

The overall availability of poultry litter offers attractive possibilities, but differences in quality of litter derived from broilers, replacement birds or layers, are very significant, as can be seen in Table 10.

Table 10
POULTRY LITTER FROM BROILERS, REPLACEMENT BIRDS AND LAYERS:
NUTRITIVE AND ECONOMIC VALUE

Source: Müller, 1976b.

The factors influencing the chemical composition, and thus the nutritional value, of poultry litter are numerous:

• nature of bedding material
• quantity of bedding material per surface unit
• density of birds per unit
• type of bird
• length of rearing period
• production intensity
• level of nutrition
• content of lactose, Mg, Cl, Na and K
• ambient temperature and humidity
• housing
• feed wastage
• litter management
• nature of ingredients in the ration
• moisture content after disposal
• type of storage
• storage time

The moisture content of litter can be controlled by dietary factors, particularly by the content of lactose, magnesium and sodium. A high DM content in litter, or in faecal poultry waste in general, can be achieved by limiting the level of critical constituents as recommended (Vogt, 1971 and 1972) below:

Further, the particle size of the feed has an impact on the birds' water intake and the moisture content of their faecal waste, finely ground ingredients increasing moisture content of excrements.

In experiments carried out by Hennig (cit. Hennig and Poppe, 1977) the following changes in the composition of broiler litter in relation to the age of broilers were observed:

Forty samples (from different broiler and meat bird farms in Czechoslovakia) subjected to macroscopic and microscopic investigation (Müller et al., 1959b) showed the following breakdown of individual components of broiler litter:

Faecal excreta and bedding are the main components, but often, due to improper management of the poultry farm, large quantities of feed can also be found in the litter, increasing the nutritive value of the waste and, in particular, its energy content.

1.1.1 Bedding material

The physical properties of bedding material include bulk density, particle size, distribution, moisture-retention capacity, compressibility, penetrability, hygroscopicity and biodegradability during the rearing period.

The chemical composition of bedding material affects the nutritive value of deep litter. An ideal bedding material for further feeding of litter has a low level of ash and its lignocellulosic constituents are biodegradable. However, the poultry farmer, primarily interested in poultry performance and not in the nutritive value of litter, does not always share this view.

The ligno-cellulosic constituents of litter vary with the quantity of bedding material per unit of floor space, and the moisture in the litter during the rearing period, which supports the activity of cellulolytic bacteria. The fibre digestibility of deep litter based on wood waste can be extraordinarily high, depending upon the biological activity of the microflora during the rearing period.

It was demonstrated in metabolism trials with sheep fed on pine sawdust prior to its use as bedding (Müller et al., 1967c) that the organic matter digestibility (OMD) was 11%, while after its use as litter its OMD value increased to 72% (for litter including droppings). Since broiler manure without bedding had 71% OMD, it appears that the potential energy of the sawdust was made available through microbial breakdown during the rearing period. This conclusion was supported by a partial disappearance of lignin, cellulose and other structural carbohydrates (based on mass balance).

Some important physical, chemical and biological properties of bedding materials are shown in Table 11.

Bedding material must be inexpensive, readily available, highly absorbent, buoyant, easy to transport, dust-free, disease-free and not consumed by the bird.

Table 11
PROPERTIES OF BEDDING MATERIALS

Source: Müller and Dřevjaný, 1967c; Müller et al., 1968; Müller, 1974–75.

Wood wastes are usually the most suitable bedding material because of their availability. Shavings are less dusty than sawdust, and sawdust of larger particle sizes is more suitable than finely-ground sawdust. Wood chips do not absorb enough moisture, and waste from soft woods appears to be better than that from hard woods because it is capable of faster biodegradation.

Cereal straw and other crop residues are basically good bedding material and contribute to the value of litter for ruminants, but when moisture content during the rearing period increases above 35%, cereal straw supports the growth of Aspergillus toxicosis. Rice hulls are not suitable bedding material for poultry or for ruminants (Müller, 1974–75; Aranjo and Pérez-Burriel, 1976). Peanut hulls are light, highly absorbent and produce an excellent bedding beneficial to both poultry and ruminants. Cottonseed hulls are good bedding material, but not too absorbent. Sugarcane bagasse, particularly pith, is quite suitable bedding material, but the danger of moulds increases with increased moisture content of litter during the rearing period and aspergillomycosis again becomes a potential threat. Peat is the most absorbent material and procudes the best poultry litter, because of a low initial pH which ties up ammonia; its disadvantage is its lack of availability and, in older peat, its high ash content.

Sand, clay and lime are not suitable bedding materials, as they have low absorption capacities, are dusty, and can be reused for feeding only in small quantities because of their ash accumulation.

Garbage compost (Müller, 1975d) has excellent absorbing properties; chickens kept on compost exhibit lower mortality (significant reduction of Eimeria spp. causing coccidiosis). Broilers reared on dried cattle manure (with straw or wood shavings) in Czechoslovakia and in Singapore (Müller and Herold, 1959; Müller, 1974) had lower mortality and a significantly better performance than those reared on any other bedding material, probably owing to the presence of known (vitamin B12) and unknown growth-promoting factors in cattle waste.

There is significant evidence that the reuse of litter in 3–5 batches has a significant impact on overall performance of poultry. Davies (1969) reported that reused litter reduces the incidence of Marek's disease. Studies on 905 flocks, totalling 15.3 million birds, confirmed that the difference in condemnation was statistically lower when litter was reused (see Table 12). According to USDA figures, this difference (0.75%) represented a saving of US$60,000. No explanation is available, but it is assumed that microbial activity in poultry litter contributes to its specific sanitation properties.

Table 12
BROILER MORTALITY: EFFECT OF NEW AND OLD LITTER

Source: Chaloupka, 1969.

The nature of the bedding material has a great influence on both poultry performance (see Table 11) and on the nutritive value of deep litter for ruminants. 44 different bedding materials have been tested by the author (Müller, 1966; Müller et al., 1968); results for the most important materials used in developing countries are given in Table 13.

Table 13
EFFECT OF BEDDING MATERIAL UPON NUTRITIVE VALUE
OF DEEP LITTER FOR CATTLE

¹ In vivo (sheep) (4 replications of each deep litter).
² Assumptions: true protein: $0.30/kg; non-protein nitrogen: $0.08/kg as crude protein equivalent or $0.50/kg as nitrogen (N); phosphorus: $0.50/kg; residual organic matter: $0.01/kg; ash content exceeding 10% is charged at $0.10/kg and deducted from the total monetary value of deep litters. Estimated costs: urea containing 46% N; $230/t; phosphoric acid (H₃PO₄) containing 27% P: $270/t.

Sources: Müller, 1966; Müller et al., 1968a.

As demonstrated by the example of rice hulls, high levels of constituents such as silica, fibre, lignin and cutin can be responsible for low ruminal digestibility.

The quantity of bedding material used per bird has also a pronounced effect on the protein and vitamin contents and the monetary value of the litter.

The addition of limestone during the rearing period results in a considerable loss of nitrogen, manifested by the displacement of ammonia, with an effect on the micro climate of the poultry house. Deep litter treated with CaCO₃ has a low level of crude and true protein (see Table 15) and the litter mineralizes rapidly.

On the other hand, supplementing litter with mineral phosphorus significantly increases the content of crude protein, especially digestible protein in vitro (see Table 16). There is usually no need to add phosphorus to ruminant rations when the litter is treated with phosphates.

The effect of bedding material on the mineral content of deep litter is shown in Table 17.

Table 14
INFLUENCE OF QUANTITY OF BEDDING MATERIAL ON CONTENT
OF NUTRIENTS IN DEEP LITTER

Source: Müller et al., 1968a.

Table 15
INFLUENCE OF LIME SUPPLEMENT TO BEDDING MATERIAL UPON NITROGEN LOSSES
(DM basis)

Source: Müller et al., 1968a.

The mineral content of litter is an important issue which will be discussed in relation to the individual classes of poultry because of large differences and variations between broilers, growing and laying birds. It can greatly influence the quality of deep litter and limit its use for feeding.

The calcium level varies generally with the level of calcium in the diet and the nature of the grit available to the birds. Phosphorus shows the same tendency. While the sodium content is usually strongly influenced by its level in the feed, the level of potassium obviously depends on the bedding material used. Higher levels of microelements (Fe, Cu, Mn, Zn) in the poultry ration usually result in higher microelement contents in the deep litter. (Müller 1967c, 1968c, 1974–75).

Table 16
EFFECT OF PHOSPHATE SUPPLEMENTATION
ON THE FEEDING VALUE OF BROILER LITTER

Note: P = Superphosphate: 40 g/m²; S = Sulphur: 1.4 g/m²; ME = Microelements mixture (10 g/m²) containing (%): 0.3 KCI; 8.0 MnSO₄. 7H₂O; 25.0 FeSO₄.7H₂O;2.0 CoCl₂. 6H₂O; 3.0 ZnSO₄. 7H₂O; 20.0 NaH₂PO₄; 41.7 CaHPO₄. 10.64 kg of bedding material per m² were used.

* Supplements not deducted.

Source: Müller et al., 1968.

Table 18 summarizes the results of comprehensive research on the effect of bedding material on vitamin content in litter (Drevjaný and Müller, 1968a).

In coniferous bedding-based litter the content of other vitamins or provitamins were analysed (Dřevjaný and Müller, 1968). The results showed contents of pyridoxine ranging from 0.5 to 5 ppm; pantothenic acid ranging from 3–35 ppm; folic acid 0.002 ppm; xantophylls ranging from 27–75 ppm.

The considerable differences in vitamin contents arise from a wide variety of causes.

On the one hand, a considerable proportion of the vitamins from the original source is not metabolized but is transferred, in an unchanged or changed form, to the deep litter. Thus, the carotene content of the litter depends on the character of the ration: the proportion of maize in the feed and the use of high-carotene feeds such as green meals. Again, since neither biosynthesis nor bacterial synthesis of vitamin E in the litter can be expected, the entire, considerable, quantity of this vitamin must be derived from amounts in the feed itself.

Table 17
MINERAL ELEMENTS IN DEEP LITTER BASED ON DIFFERENT BEDDING MATERIALS
(on DM)

OM = Original bedding material;
DL = Deep litter.

Source: Müller, 1968.

Table 18
EFFECT OF BEDDING MATERIAL ON VITAMIN CONTENT OF LITTER
(ppm)

Source: Dřevjaný and Müller, 1968a.

On the other hand, however, the levels of the vitamin B complex are usually higher than the quantities present, naturally or as supplements, in poultry feed. Part of this increase is due to enteric biosynthesis, since a substantial portion of vitamin B content is the product of endogenous synthesis in the digestive tract. Another important factor lies however in the fermentation conditions of individual types of litter: humidity, temperature and the presence of inorganic nutrients, the intensity of this biosynthesis being supported further by the nature of the substrate, management and nutrient supply (Müller et al., 1959). The greatest increase is that of vitamin B₁₂, present at more than 100 times the level in the original feed. That this increase derives from biosynthesis is indicated by the isolation of Actinomycetes and other vitamin B₁₂-producing micro-organisms from litter. The level of vitamin B₁₂ can be substantially enhanced by supplementing litter with traces of cobalt and cyanides (Müller and Herold, 1959).

It has been observed that greater proportions of β and γ-tocopherols to the δ isomer are found in deep litter than in the feed (see Table 19 below). It follows that the chicks make a greater utilization of the α isomer than of the other isomers.

Table 19
TOCOPHEROL ISOMERS IN BROILER FEED AND DEEP LITTER

Source: Müller, 1968c.

The effect of bedding material on antibiotic levels in deep litter was studied by Müller and Dřevjaný (1967c). There was a remarkable, highly significant difference in the content of chlortetracycline (CTC) in different bedding materials, as shown in Table 20. The results suggest that CTC activity in faecal waste, derived from the feed, can be inactivated to a large extent by the specific chemical properties of deep litter, and appears to be related to the pH and moisture content.

Table 20
EFFECT OF BEDDING MATERIAL ON CHLORTETRACYCLINE LEVEL IN DEEP LITTER

Source: Müller, 1967c.
Note: CTC levels in broiler starter and finisher feeds were 60 and 50 ppm respectively.

1.1.2 Broiler litter

Broiler litter is the most valuable animal waste because of its high protein content, of which about 45–67% is present as true protein, 18–30% as uric acid and 12–17% as ammonia. A smaller amount is represented by creatine (2–4%) and other N constituents. In comparison to other animal wastes, broiler litter is also relatively high in feed energy. In trials with sheep, Fontenot et al., (1966) reported a TDN value for broiler litter 59.8% (on dry basis); Dřevjany and Müller (1967) in digestion trials with steers (160–180 kg) realized an average TDN value of 52% (range 46–61%) and in 13 samples of broiler litter collected recently in Mauritius (Müller, 1975, 1978), it was found that a calculated TDN value for ruminants was between 62 and 67%. This high value was apparently attributable to broiler litter with low ash content (7.6–14.1%).

Table 21 presents the nutrient composition of broiler litter.

There are remarkable differences between individual countries and it appears that much depends upon the environment, the management of the poultry houses, and the litter.

Broiler litter is reused in the USA; it usually originates from several batches (three or more), while samples from Mauritius, Czechoslovakia and Southeast Asia are always from one batch only.

The variation in protein content is apparently influenced by the level of bedding, the moisture content of the litter during the rearing period, the temperature and pH of the bedding material and several other factors which have been previously discussed.

In an experiment carried out by Dřevjaný and Müller (1968), it was demonstrated that about one-third of the fibre contained in the litter derived from excreta and two-thirds from the bedding material. The biodegradability of bedding material has a significant effect on the crude fibre content of the litter. Thus, for example, in calculating the mass balance, the highest “losses” on fibre were observed in litters based on groundnut hulls (29.3%), maize cobs (29.2%) and sugarbeet pulp (26.4%), while some other less degradable material exhibited only 1.8% (sunflower hulls), 0.5% (cocoa hulls) and 8.9% (wood shavings/sawdust) disappearance of crude fibre. These “losses” are attributable to changes and shifts (e.g. from crude fibre to NFE) in the composition of structural carbohydrates of easily degradable bedding materials.

The ash contents of litters of different origin can be influenced by the addition of soil, grit and lime, but the high ash content of reused litter is a result not only of ash accumulation but also, to some extent, of the mineralization of organic matter.

Calcium in broiler litter originates in the feed; the P:Ca ratio is usually 1:1.1–1.3 which ensures that ruminant diets based on broiler litter are well balanced in these two basic elements. Critical constituents of broiler litter are microelements, especially copper, but these aspects will be discussed in detail in Chapter 2.

1.1.3 Replacement bird litter

Replacement bird litter derives either from light or heavy poultry breeds. Their litter is considerably lower in nutrients because replacement birds are reared at a lower density than broilers and usually use more bedding material. In addition, the plane of nutrition is lower, because about 70% of the feed intake derives from the “developing ration” containing only 14% protein or less; furthermore the developing ration is deliberately high in crude fibre and other undigestibles to restrict the feed intake of the growing birds. For these reasons the faecal waste, and thus the litter, produced by replacement birds is of a poorer quality than that of broilers (see Table 22).

1.1.4 Laying house litter

The proportion of bedding material to layer excreta is somewhat higher in layer litter than in broiler litter, so that more fibre and other undigestibles are inevitably accumulated in this waste. The usual level of crude protein ranges from 16 to 22%, the main crude protein components being uric acid (about 55%), protein-bound protein (36%) and ammoniacal protein (9%). Ether extract usually ranges from 1.1 to 1.8% because of the different composition of the laying diet, which usually contains a substantial volume of solvent-extracted milling by-products.

Table 21
BROILER LITTER: NUTRIENT COMPOSITION

Table 22
COMPOSITION OF LITTER FROM REPLACEMENT BIRDS

Source: Unpublished data (Müller).

Crude fibre in laying house litter varies considerably with the quantity of bedding material used and overall management; the average is around 20.6%. Ash ranges from 26 to 32%. The calcium level is always high (approximately 6%), while the phosphorus level is comparatively low (1.8 to 2.4%).

Since the nutritional value of laying-hen litter can vary considerably, it is almost impossible to establish average values. It is always necessary to analyse the litter prior to its use as a feed.

1.2 POULTRY-BATTERY MANURE

The following tentative standard for dried dehydrated poultry waste has been formulated:

“Dried Poultry Waste (DPW) is a product composed of freshly collected faeces from commercial laying or broiler flocks not receiving medicants. It shall be thermally dehydrated to a moisture content of not more than 15%. It shall not contain any substances at harmful levels. It shall be free of extraneous materials such as wire, glass, nails, etc. The product shall be labelled to show the minumum percent protein, minimum fat and percent fibre. It may be used as an ingredient in sheep, lamb, beef and dairy cattle, broiler and layer chick feeds. Broiler and laying rations shall be limited to 20% and 25% DPW, respectively.”

For every kg of eggs, a hen produces 4 kg of fresh manure or 1 kg of manure dry matter.

Several investigators (Van Slyke, 1939; Donaldson, 1943; Salter and Schollenberger, 1939; White et al., 1944) indicate that the quantity of manure varies with the breeds and the live weight of the bird, the time of collection, the composition of the diet, the plane of nutrition, the feed intake, the climate and other factors. The results of a study of the quantity of manure produced by different breeds are given in Table 23.

In reality, the collectable quantities of manure are much lower (55–65%) because of the losses resulting from the speedy decomposition of organic matter (see Table 24).

Table 23
QUANTITY OF HEN MANURE PRODUCED BY VARIOUS BREEDS

Source: Papanos and Brown, 1950.

Table 24
ESTIMATED LOSSES OF ORGANIC MATTER AND OTHER CRITICAL NUTRIENTS
IN POULTRY MANURE DURING STORAGE
(on DM)

Source: Müller, 1977.

The losses of nitrogen in fresh layer manure reported by Flegal et al. (1972) were as follows:

More frequent collection of manure reduces losses of organic matter, crude protein and other valuable nutrients. Moisture and high temperature are the main factors speeding up the enzymatic breakdown of organic N from uric acid and urea into inorganic forms of nitrogen:

CO (NH₂)₂ + 2H₂O → (NH₄)₂ CO₃ → 2NH₃ + CO₂ + H₂O

Two possibilities for preventing losses of organic N in poultry manure are to reduce moisture (wooden slats, air movement) or to use chemicals which react with free ammonia. In this respect the application of single superphosphate or phosphoric acid has been successfully tested (Müller et al., 1968). Chemical control may also be achieved by other mineral acids (H₂SO₄, HCI) and formalin, which inhibits bacterial activity but only for 5–14 days (see Section 3.4).

Fresh poultry manure has a rather low content of ammoniacal nitrogen that increases rapidly. Moisture and temperature, as mentioned above, appear to be the main factors contributing to the speedy decomposition of fresh manure. Chang et al. (1975) demonstrated that the storage temperature has a strong influence on the amount of ammonia in excreta, amounts rising with the time of storage. Their results, summarized in Table 25, show that within 3½ hours there is more than a six-fold increase in ammonia over the amount present at the time of collection.

It is pertinent to note that the zero hour sample was in reality processed about 30 minutes after excretion (the time required for handling and preparation of the sample), and it is quite possible that the changes take place even much earlier.

Poultry manure is not a product of uniform quality. Although the crude protein is usually calculated at about 30%, it may range from 40% down to 18%. It is represented by about 37–45% true protein, 28–55% uric acid, 8–15% ammonia, 3–10% urea, creatine and other nitrogenous compounds. The source of protein in the layer diet influences the ratio of N fractions; fish meal, in comparison with dried skim milk as a main source of protein, produced 31% less uric acid but 6% more true protein in manure (White et al., 1944).

Table 25
AMMONIA CONTENT OF COMPOSITE HEN EXCRETA SAMPLES

Source: Chang et al., 1975.

A high-plane nutrition yields manure rich in nitrogen and minerals, while low-plane nutrition results in higher fibre content. Moran and Evans (1976) fed laying hens with two extreme rations varying in crude protein (18 vs. 14%) metabolizable energy (2.75 vs. 2.4 Mcal/kg) calcium (3.5 vs. 3.25%) and phosphorus (0.55 vs. 0.50%). The uric acid content of the manure was about three times higher in hens fed the high protein-energy diet than in birds on low-plane nutrition (4.25–4.56% vs. 1.69–2.1%). As for the other nitrogenous constituents (soluble NPN, NH₃) there were only slight differences between high-and low-plane nutrition, with a logical trend of higher values for high planes.

The biological availability of protein from dried layer manure was investigated by Polin and Chee (1975). They found an agreement between chemical and biological determinations, suggesting that chemically determined true protein appears to be a good assessment of the available true protein in poultry manure.

In five in vivo digestibility trials on sheep, Henning et al. (1975) tested broiler manure, containing 38.2–41.15% crude protein, and young pullet manure, containing 30.7% crude protein, with the following results:

¹ German feed energy unit.

The results convincingly demonstrated that both faecal wastes have protein values comparable to conventional protein feeds.

The amino acid composition of layer manure has been studied by several authors. The results obtained by Flegal et al. (1971) indicated (Table 26) that layer manure is a rather good source of an important amino acid (cystine) but that basically the waste, being high in NPN and in non-essential amino acids, has greater feeding potential for ruminants than for monogastrics.

Table 26
DRIED LAYER WASTE (DLW): AMINO ACID COMPOSITION

Source: Flegal et al., 1971.

1.3 CATTLE MANURE

Pioneer work on the nutritive potential of cattle manure as a feed for cattle has been carried out in the United States by Anthony of Auburn University, Alabama (1969a,b, 1970, 1971a,b). His research was given added impetus by the important discovery (Ciordia and Anthony, 1969) that parasitic nematode infection cannot be transmitted by fermented manure. Further experiments have conclusively proved that fermentation during the ensiling process eliminates most of the pathogenic microbes.

The quantity and quality of dairy manure is related to the body weight of the cow, milk yield, composition of the ration, water consumption and environment. A dairy cow of 500 kg live weight, producing 15 litres of milk, yields approximately 35 kg of fresh manure per day, containing about 88% moisture or 4.2 kg dry matter which includes solids of the manure and urine. The moisture content of faeces usually ranges from 80 to 85% and that of urine from 94 to 96%. The composition of dairy manure varies considerably with the composition and nature of the diet (forage vs. concentrates) (Table 27).

The breakdown of nitrogenous substances in manure from various classes of cattle is given in Table 28.

The prevailing volatile fatty acid in fermented manure (within 1–4 days) is lactic acid; its level is responsible for a pH value ranging from 4.7 to 6.5.

The content of organic matter of dairy manure is 86–90%, and that of mineral matter 10–14%, but the ratio varies considerably with diet composition.

Table 29 presents the results of the University of Nebraska's lamb metabolism experiments (cit. by Wagner, 1977) with different planes of nutrition. The findings clearly proved that the level of digested and excreted dry matter is strongly influenced by the feeding regime, in particular the forage concentrate ratio.

Remarkable differences in the nutritive value of the liquid and solid fractions of cattle manure were found by Menear and Smith (1973). In their tests, involving a continuously fed screw-press, they obtained two fractions with greatly differing physical and chemical properties (Table 30). While the press cake (solid fraction) was high in cell-wall content, the liquid fraction was rich in crude protein, at a level comparable with that of soybean meal. The quantity of nitrogen recovered in the liquid fraction averaged 44%. In addition, the liquid fraction, being low in cell-walls, could serve as protein concentrate for cattle and other livestock species.

Table 27
MANURE COMPOSITION OF COWS FED DIFFERENT DIETS

¹ Reference: Method of Saeman, J.F., W.E. Moore, R.L. Mitchell, and M.A. Millet. 1954. TAPPI 37: 336.
^2,3 A composite of four faecal samples from each group was used for testing.

Source: W.B. Anthony, 1972.

Table 28
CATTLE MANURE: NITROGEN COMPONENTS
(N x 6.25)

Table 29
INFLUENCE OF DIET ON DIGESTIBILITY AND COMPOSITION OF EXCRETA

¹ Neutral detergent fibre.
² Neutral detergent solubles.

Source: Wagner, 1977.

Table 30
CATTLE MANURE AND ITS SEPARATED FRACTIONS: CHEMICAL COMPOSITION

¹ Average of three trials.

Source: Menear and Smith, 1973.

1.3.1 Cattle litter

Cattle litter has a nutritive value similar to that of cattle manure. However, the litter also contains bedding material, mostly of cellulosic origin, such as wood shavings, cereal straw, or other rural by-products suitable for bedding.

Table 31
CATTLE LITTER: CHEMICAL COMPOSITION
(on DM)

¹ Müller, 1959.
² Müller et al., 1974.

The nutritive properties of cattle litter reflect the nature, quantity and ratio of bedding material used. The litter is sometimes kept for many months, or even years, without being processed or cleared. Such treatment has a great influence on its chemical composition and thus its nutritive value. The digestibility of fibre increases the longer the bedding material is exposed to cattle, but crude protein and organic matter in older cattle litters decreases correspondingly.

1.3.2 Feedlot manure

Under certain conditions, feedlot waste can also constitute a significant part of cattle diets. Much depends, however, on several factors, mainly the ratio of organic and inorganic matter (Johnson, 1972). Feedlot wastes containing more than 45% ash (inorganic matter) are not suitable for direct feeding. Typical chemical compositions of feedlot waste are shown in Table 32.

Table 32
FEEDLOT WASTES: COMPOSITION

¹ Texas County feedlot.
² Arkansas Valley feedlot, growing lots.
³ Arkansas Valley feedlot, finishing lots.

Source: Johnson, 1972.

1.4 PIG WASTE

The chemical composition and quantity of pig waste depends upon several factors: age, live weight, breed, feed and water intake, digestibility of the ration, housing, environment and waste management.

The production of solid pig waste ranges from 0.6 to 1.0% of dry matter per day calculated on body weight. Low-digestibility rations yield relatively more manure. With the increase of body weight the quantity of pig waste decreases significantly (Tietjen, 1966, cit. by Henning and Poppe, 1977).

Table 33
PIG WASTE: EFFECT OF WEIGHT CATEGORY ON QUANTITY

Faeces represent about 46% and urine 54% of wastes on fresh basis, but on dry basis faeces represent 77% and urine 23%. The pH of pig manure is in the range 7.2–8.3. The chemical composition of manure also changes rapidly with time after excretion (Harmon, 1974).

The biochemical routes of bacterial decomposition of manure can be divided into the aerobic process (resulting in carbon dioxide, nitrites, and nitrates, dissolved nitrogen and soluble sulphates) and anaerobic action (yielding gases such as methane, ammonia, hydrogen sulphate and carbon dioxide).

Australian scientists of the University of Melbourne have contributed greatly to knowlegde of the chemical composition of pig manure. In comprehensive studies Pearce (1977b) documented a large volume of analytical data from 24 commercial piggeries which appear in Table 34.

Table 34
PIG FAECES: COMPOSITION
(on DM)

Source: Pearce, 1977b.

In several samples of processed pig waste it was found that the vitamin A content averages 1,600 IU/kg (Hennig and Poppe, 1977).

The great variability in individual constituents of faeces is attributable to the classes of pigs, composition of diets, plane of nutrition and mineral supplementation.

A comparison relating feed nutrients to faecal nutrients was made by Hilliard (1977). His results, which appear in Table 35, clearly reflected the digestible capacity of pig for individual nutrients. In this respect lignin, ADF, cellulose and fibre were practically undigested, as demonstrated by their accumulation in faeces.

Table 35
PIG FEED AND FAECES: COMPOSITION

Source: Hilliard, 1977.

Waste management and processing systems have a great impact on changes in the amino acid composition of pig waste (see Table 36) as reported by several authors (Gouwens, 1966; Orr et al., 1973; Harmon et al., 1972; Harmon, 1974).

Table 36
PIG FAECES: AMINO ACID COMPOSITION
(% DM)

Source:
1. Gouwens, 1966;
2. and 4. Orr et al., 1973;
3. Harmon et al., 1972b, cit. by Harmon, 1974.

Danish scientists (Eggum and Christensen, 1973) found that 60% of the crude protein in pig manure was biologically available and that its biological value was 70%. Amino acid analyses indicated that pig manure protein is rich in lysine (5.24% lysine, compared to barley, 3.65% lysine) and other essential amino acids (methionine, threonine), which usually limit the feeding ration for pigs.

The protein value of pig and several other animal wastes was determined in two trials on rats by Chastain et al. (1976). Aerobically and anaerobically treated pig wastes were compared with layer and broiler manure and dairy slab-wastes. Individual wastes were incorporated into a maize-soybean diet to substitute for 20, 30, 40 and 92% of crude protein. The average daily gain in both trials using diets with 20 or 30% waste-based dietary protein was similar to that of groups fed a control maize-soybean diet without waste protein. Higher substitution of protein by waste (40% and 92%) reduced live-weight gain and feed efficiency of all waste protein-based diets, although a severe depression of growth and feed intake was observed at the highest level of substitution (92% of dietary protein). Addition of molasses at 5% level markedly improved the feed intake of all waste protein-based diets.

These experiments on rats showed that even monogastric animals are capable of utilizing protein contained in pig and other animal wastes provided that the diets are carefully balanced.