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Practical technologies to optimise feed resource utilisation in reference to the needs of animal agriculture in developing countries

by R.A. Leng


Production from a herd or flock of ruminants is a result of the interactions of environment, the animals nutrition, and its genotype.

Individual productivity from most ruminants in all developing countries is low. The reasons for this are complex but in order of priority appear to be:

Genotype is over-emphasised as a primary constraint as poor nutrition has an overwhelming effect. Resistance to disease and high temperatures of particular breeds is however an important overall consideration.

Recent nutritional research has demonstrated the possibility of very large increases in animal production that can be achieved by small alterations to the feed base (see Leng, 1991). As these increases have also been achieved at the farm level (see NDDB report, 1989) without alteration to the other management practices, it demonstrates the large impact potential of the feeding strategies in the present environment. Increased production of meat/milk with better body condition of animals also lifts lifetime reproduction rates. The lowering of the age at puberty of heifers and a decrease in the intercalving interval in cows have probably the greatest effect on the overall level of production.

Increased efficiency of utilisation of forage by the animals together with improved reproduction rates have demonstrated that production can be increased by up to five fold without changing the basal feed resources. This has been achieved, by providing the critical catalytic nutrients that are deficient in the diets and by balancing availability of nutrients closer to requirements.

In general, the supplements required are urea/minerals and a source of bypass protein. In many countries these supplements are already available, in others, there is a need to manipulate these resources, to provide them in the correct amounts and in the appropriate form.

In many grazing areas the basic resources are not available locally. Research and development is needed to produce them economically at the centres of ruminant population densities. In the rangelands, particularly in the semi arid areas, tree forages, seeds and pods represent by far the greatest potential source of protein meals.


Throughout the last thirty years the expansion of crop and livestock production in developing countries have more than doubled but the increase in demand for food has been even greater, leading to an increase of food imports by approximately 10% per year. This situation is expected to remain at the same rate for the foreseeable future.

The increased production of animal products in developing countries has been largely through increased animal numbers, while production per animal has been static or increased to a minor extent over a long period of time (Jackson, 1981). The demand for food for humans in these countries is likely to increase and, since cropping land is almost fully utilised at the present time, it appears that cultivated pasture is likely to become scarcer in most parts of the developing world.

The ruminants niche is likely to remain as a utilizer of carbohydrate biomass which is not digested by intestinal enzymes and, therefore requires fermentative digestion, and which cannot be used extensively by monogastric animals (i.e. forage, crop residues etc.). The ability of ruminants to convert otherwise waste biomass into meat, milk and other products and to accomplish work suggests that they will endure into the foreseeable future. The ever increasing pressure on land for crop production suggests, however, that they will have to continue to do this utilizing crop residues, industrial by-products and pastures from relatively infertile rangelands. The common characteristics of such feeds are low digestibility, low protein content and a low mineral component.


Animal Productivity from Available Feed Resources

Research over the last twenty years clearly indicates that it has been a popular misconception that low productivity of ruminants in developing countries is a result of low energy density of the available forages (i.e. low digestibility). This concept, often repeated in reviews, even up to the present time, is misleading. There is now abundant evidence that low productivity stems from an inefficient utilisation of the feed because of deficiencies in the diet. These deficiencies are of nutrients critical to the well being of the microbes which ferment or digest the feed, and nutrients required to balance the products of digestion to requirements. This has been considered in detail recently by Leng (1991), who suggested that because an inefficient utilisation of nutrients increases metabolic heat, that the often low intakes of poor quality forage of ruminants in the tropics (where most developing countries exist) is imposed by a combination of climatic and metabolic heat stress (Leng, 1989). Correction of a nutrient imbalance by feeding a bypass protein often (but not always) increases the intake of poor quality forages to a constant intake of around 80-100 g/kg0.75/d (see Fig. 1). Tropical conditions impose this particular feed intake constraint on ruminants for a considerable period of a feed year and it is rarely seen in temperate areas. On the other hand cattle in the tropics require less feed for maintenance, if they do not have to combat cold stress, and if they can process these extra nutrients they can be more efficient than animals on the same feed in a cold climate. To process the extra nutrients however, they need extra protein and thus the requirements for amino acids are higher in cattle in the tropics then in animals on the same feed in cold environments.

Figure 1: Intake of low digestibility forages by cattle either unsupplemented or supplemented with bypass protein or bypass protein and urea (Lindsay and Loxton, 1981; Lindsay et al., 1982; Hennessy, 1984, Perdok, 1987; Kellaway and Leibholz, 1981).

Figure 1

Productivity Levels Achievable by Ruminants on Low Quality Forage Based Diets

The rationale and concepts on which the following discussions will be centred have been reviewed by Preston and Leng (1987) and Leng (1989,1991). The basic concepts are as follows. Ruminants fed low quality forages require supplementation with critically deficient nutrients to optimise productivity. The supplements that are required:

The nature of anaerobic microbial fermentation in the rumen indicates that microbial cell growth in the rumen (which supplies the protein {P} to the animal) relative to the production of VFAs (E) (the major source of oxidisable substrate for ATP generation), will be extremely low in nutrient deficient rumen medium or digesta. This means that a sub-optimal level of any nutrient for microbial growth in the rumen will result in low protein to energy (P/E) ratio in the nutrients absorbed. Ensuring a nutrient non-limited microbial digestion in the rumen by supplementation automatically improves the P/E ratio in the nutrients available to the animal. Feeding a protein meal in which the protein has been made insoluble or otherwise not attacked by rumen microbes, is a further major method for adjusting the P/E ratio upwards.

The ratio of microbial proteins to VFA produced and the effects of supplementation in a steer given 4kg of organic matter which is completely digested in the rumen is shown in Table 1 for a number of feeding conditions.

The reason for discussing these theoretical calculations at this point is to emphasise the large differences in protein to energy (from 12 to 50) in the nutrients absorbed by ruminants, fed unbalanced diets and diets balanced with supplements. It also emphasises that on a diet high in bypass protein the rumen microbes need not be highly efficient. To obtain the higher P/E ratio without supplementation, however, to directly improve rumen condition, more bypass protein is needed.

Table 1. The effects on P/E ratio in the nutrients absorbed of supplementation with a bypass protein to cattle with a poor or optimised (i.e. supplemented) microbial milieu in the rumen. The values are calculated for a steer digesting 4 kg DM in the rumen (see Leng, 1982)

Rumen environment protein
Protein bypass
(g prot/d)
Microbial cells ProducedProtein microbial
VFA produced

* Microbial protein plus dietary protein to VFA energy.

** Although the rumen environment is deemed not to change through the addition of protein meal, in fact it will have been improved but may not be optimised to the extent it would by feeding a molasses/urea block. P/E ratio here is underestimated.

It is the relationship of P/E with the efficiency of feed utilisation that has a very large effect on growth, milk yield and reproductive performance. The levels of production achieved when P/E is increased have been greatly superior to that predicted from present day feeding standards based on the metabolisable energy of a feed.


Most forages consumed by livestock in developing countries have a low digestibility which rarely exceeds 55% and is mostly in the range of 40-45%. The calculated metabolisable energy in the dry matter (M/D) thus ranges from 7.5 down to 4.8. Feeding standards indicate that feeds with a metabolisable energy content of 7.5 will support growth rates of cattle of approximately 2 g/MJ of M/E intake. On a forage at the lowest level of ME, cattle would be in negative energy balance (see ARC, 1980 and also for reference Webster, 1989)

Figure 2: Schematic relationship between diet quality (metabolisable energy/kg dry matter) and food conversion efficiency (g liveweight gain/MJ ME) from Webster, 1989.

The relationships found in practice with cattle fed on straw or ammoniated straw with increasing level of supplementation in Australia (♦, o, •) (Perdok et al., 1988), Thailand (∆) (Wanapat et al., 1986) and Bangladesh (□) (Saadullah, 1984). Recent relationships developed for cattle fed silages supplemented with fish proteins (Olafsson and Gudmundsson, 1990)(Ä) and tropical pastures supplemented with cottonseed meal (Godoy and Chicco, 1990)(*) are also shown. This illustrates the marked differences that result when supplements high in protein are given to cattle on diets of low ME/kg DM.

Figure 2

Contrast this with results of supplementary feeding trials based on balancing the nutrition of animals with urea/minerals and bypass protein, where cattle growth rates equivalent to 18 g/MJ of M/E intake have been achieved in cattle fed straw (see Fig. 2). Obviously the presently accepted feeding standards (see ARC, 1980) have been very misleading and can not be used as a means of predicting animal performance. Of vital importance however, is that the application of the concept of balanced nutrition can improve animal growth by 2–3 fold and the efficiency of animal growth by as much as six fold over previous estimates (a range of 2–10 fold). In addition it also shows that although growth rates of cattle are below those on grain based diets cattle on forage based diets can be as efficient in converting feed to liveweight gain.

Low productivity of ruminant livestock has been accepted in developing countries as an inevitable result of the poor feed base and a low feed conversion efficiency. The concept being that there is a large heat production (energy requirement) associated with the ingestion and movement of digesta along the tract in animals fed on forages as compared to concentrates (see Ørskov and MacLeod, 1990). This conclusion is clearly contrary to the conclusions of Leng (1991) and the concept of balanced nutrition presented here.

However, poor growth rates are associated with a slow maturity and, on poor quality roughage diets, cattle reach puberty at four to five years of age and often have a calving interval of 2 years. Recent observations on balancing the nutrition of cattle on such forages indicate that it is possible to reduce age at puberty by one to two years and potentially possible to support a calf every year on these same feed resources. Management considerations, however, suggested that 15 months calving interval is more likely. The flow-on effects of improved reproduction are: increased percentage of a herd in production and an increased offtake of animals. The flow-on from improved reproduction outstrips the direct effects on immediate liveweight gain or milk yield.


Even though the principles of feeding bypass protein to improve productivity have been known for many years, application has been slow and unspectacular, particularly in the developing countries. The application has been slowed by:

However, wide scale application of the use of supplements high in bypass protein have occurred in India through the initiatives of The National Dairy Board of India (NDDB). For the same reasons as given above, progress was initially slow (development started in 1980) but it is now accelerating at a pace which should see most feed mills in India dedicated to the production of bypass protein supplements in the next five years. At the present time approximately 100 MT of bypass protein feed is being fed daily to their dairy animals by small village farmers. In many situations, this is coupled with the use of a molasses urea block, particularly by the more advanced farmers (see NDDB report, 1989).

After considerable experimentation and village testing of a bypass protein supplements, the management of the cooperative feed mill in Kedah district in India decided to convert from the production of concentrates based on traditional concepts to a bypass protein concentrate (30% CP) composed of locally available protein meals plus 10% grain and approximately 10% molasses. After pelleting, the protein in the concentrate was found to be 75% insoluble in buffer solution (Leng and Kunju, 1988)

The marketing strategy was to widely advertise the new feed concentrate with a simple statement that village farmers should ---- “feed to their dairy animals half the weight of the usual concentrate and this would double milk production”. As the feed was about a third more expensive, there was some considerable opposition to its introduction. Nevertheless, the feed mill (capacity 100 MT/day) was converted to the production of new feeds on December 1st 1988. The feed was purchased, somewhat reluctantly by some of the farmers, but all opposition to its supply appeared to have been overcome by the middle of the next hot dry period (April-June) when milk yields were considerably above previous years with only half the weight of supplement.

The collection of milk within the dairy co-operative, relative to the feeding of the traditional and new feed supplement for the previous five years and for the twelve months since conversion to the new feeding systems are shown in Figure 3. Whilst a number of changes have occurred in the area which could contribute to the increased milk collected, from the research carried out by NDDB prior to the change over the responses in milk yield are in line with observed increases in milk collected (see Kunju and Leng, 1988).

The effects of the changed feeding appear to be a 30–50% increase in milk production, from Dec. 1st. 1988 to Dec. 1st. 1989 - a further similar increase in production is apparent in 1989-1990 (unpublished observation). The further increase probably represents the flow-on effect that would come from increased reproduction rate that should have resulted from the new feeding systems.

Figure 3: Milk collection records and the sale of supplements in for the Co-operative in the Kedah district of India when supplements were compounded on traditional concepts (1985–1987) and following (1st December, 1988) their replacement with a 30% C.P. bypass protein pellet (records provided by the NDDB of India).

Figure 3

Impact of New Feeding Systems on Milch Herd Composition

Undoubtedly the new feeding systems, combined with disease control and better management, is facilitating the introduction of cows with a higher genetic potential for milk production. The apparent lowering of heat stress through the balanced approach to nutrition has also allowed Friesians (the mothers of bulls that will be used for cross breeding purposes) and selected buffaloes, to yield milk well above the average reported for the developed countries. The yields of imported Friesian cows from Germany fed on all roughage diets supplemented with a molasses/urea block and a bypass protein (recommended at 350 g/litre of milk) at Anand averaged over 5,000 litres/305 day lactation in 1988–89 with individual milk yields of over 6,000 litres/305 day.

These milk yields are achieved in an area of India considered to have one of it's hottest climates. Higher yields were observed with Friesians managed by village farmers in a more temperate area of India (Bangalore).


Provision of Minerals

It is not practical to identify the major critical micro and macro minerals in a basal roughage diet, as these will vary from site to site and year to year. The practical approach is one of ‘rules of thumb’ that provide a best bet or ‘shot-gun mixture’ of minerals as economically as possible. A concentrated plant extract, such as, molasses provides such mixtures and can be fortified for specific areas where local knowledge points to specific deficiencies. In this respect, molasses (both sugar cane and beet) and concentrated palm oil sludge offer useful sources of these minerals. They are also quite palatable to livestock and are useful in hiding less palatable nutrient sources in supplements.

Mineral salt mixtures are commercially available in most countries. They usually have a high content of salt and only minor quantities of the trace elements. In practice, fortified materials, such as molasses, will be superior to commercial mixtures as they present a greater coverage of all the minerals required, also thy are a valuable source of other nutrients (e.g. B vitamins) and a small amount fermentable energy.

Supplying the Rumen Microbes with Ammonia/Urea

The other requirement is for a non-protein nitrogen source for the rumen microbes, usually urea. Urea is usually administered together with the minerals and its concentration in such mixtures is controlled by safety and ease of incorporation and, therefore, rarely exceeds 10–15% of such mixtures. However, this is usually sufficient to allow an intake of between 50 and 100 g of urea by cattle from a molasses/urea block which is sufficient to balance ammonia in the rumen of cattle on a low N roughage diet.

Results from India suggest that mineral/urea mixtures in, for example, molasses multi-nutrient blocks, are best given ad libitum allowing the animal some degree of selection and there are indications that the animal will learn to control the intake of urea to an optimal level.

Bypass Protein Supplements

Providing bypass protein to cattle under small farmer management is often difficult and, at times, is too expensive. There is often little information on the locally available protein sources, particularly the level of protection of the protein in the rumen. As a rule-of-thumb, solvent extracted oilseed cakes, fish meal that has been flame dried (but not sundried or fish silage) and protein sources that have been heat treated, have considerable protection from rumen degradation. The degree of protection is enhanced by pelleting the protein meal in the presence of free glucose or fructose, (as occurs in molasses) when a mild browning reaction occurs (unpublished observations).

The turning over to supply bypass protein rather than concentrate for supplementing the cattle of small farmers, the National Dairy Development Board of India converted the existing feed mills to the production of high protein supplements. Wherever possible, solvent extracted oilseed meals form the basis of the supplement. However, the protein ingredients have to be purchased on the open market and leastcost formulation is desirable because of the size of the production unit (50–100 MT/d.). The high degree of protection of these protein feeds is achieved by ensuring a high proportion of solvent extracted meal and also by heat pelleting with 8% molasses in the mixture.


India is fortunate in having large amounts of crop residues high in protein, most of which have a fair degree of protection brought about by the processing methods. These materials are convenient to use in existing feed mills with the available equipment (i.e. grinders, mixers and pelleters) and the pelleted supplement is readily accepted because of a well developed marketing strategy.

In many other countries, particularly in extensive grasslands or savannahs, where major constraints to production of cattle are essentially the same as those for cattle fed crop residues, protein sources may not be readily available, or the sources not so obvious or easily obtainable. Most legume forages, legume seeds, edible tree leaves, seed pods and seeds that are available in these areas, contain highly soluble proteins which is easily fermented in the rumen. These, when used as supplements, only provide ammonia and minerals (they have for example 0.5-1% phosphorus). Fed without processing, because of their influence in the rumen they generally increase production of cattle on a basal diet of low protein roughage, but they provide little bypass protein unless they are fed as a large proportion of the total diet. Research results in Colombia fit into the general concept where supplementation of cattle on green Brachiaria decumbens pasture with either urea/molasses or the foliage of the fodder tree Glyricidia, increased production to the same extent (see Table 2).

Table 2: The effects of feed supplementation on livestock gain of cattle (6 per group) grazing on green Brachiaria decumbens pastures in the wet season (with mineral supplements) with liquid molasses/urea 10% or Glyricidia foliage.

TreatmentRumen Ammonia
Wt (kg)
WT (kg)
LWt gain
No supplement50194244580
+ Glyricidia170204266717
+ Molasses/Urea250203269751

(Source: ICA, 1988)

Protein that is fermented in the rumen yields 80–100 g of microbial protein/kg of protein consumed. Whereas carbohydrate yields 180–200 g of microbial protein/kg of carbohydrate. On a high nitrogen diet, a significant supplement of soluble protein could in fact imbalance the P/E ratio because of the low microbial growth efficiency. This is a possible explanation for recent results reported from Iceland where fish silage and fish meal were compared as protein supplements to ‘high quality’ grass silage fed to young cattle (see Table 3). Fish silage, with the same N content as a fish meal supplement, depressed liveweight gain by 90g/day whereas a fish meal supplement improved liveweight gain by 360 g/day at the same N intake.

Table 3: The effect of supplementation of a basal grass silage * diet with fish meal or fish silage on liveweight gain and efficiency of feed conversion (after Olafsson and Gudmundsson, 1990).

SuppleentIntake (kg/d) SupplementSilage DMLWt gain
Calculated ME intakeEfficiency (gLWt gain/MJ ME)

* Early cut, precision chopped and preserved with formic acid, DM In vitro DMD. = 73% Calculated M/D = 10.4. CP = 16.8%. Cattle were Galloway/Icelandic cross - 6 months (8/group treatment), 160–205 kg LWt at beginning of experiment.

The above discussion defines and highlights two potential strategies to provide the two types of supplement required to optimise the efficiency of feed utilisation of cattle in areas with scarce resources of nitrogen or protein. The strategies must be to find forages/trees/tree seeds or pods that are high in protein and minerals. To then use this material in small supplements to provide for either the rumen with soluble protein and minerals or bypass protein after treatment to protect the protein. These uses can be combined with either a molasses/urea block and/or a source of locally available bypass protein.

Processing of Local Protein Resources to Provide Bypass Protein

The protein and render them non-fermentable in the rumen but allow them to retain digestibility in the intestines. In general, these fall into chemical treatment with agents that cross link with amino acids on the protein chain and include formaldehydes and aldehydes, tannins and simple sugars such as glucose and xylose. These reactions often require the protein source to be heated during processing. Heat alone will often denature the protein to effect protection. For instance, Goering and Waldo (1974) found significant effects of the temperature used to dry lucerne on the subsequent animal production from that lucerne. In general, the higher the temperature of drying the greater the retention of protein by the animal. More recently, Lewis et al. (1988) have demonstrated that mild heat with a small amount of xylose is very effective in protecting soya bean meal protein (see Table 4). Xylose can be readily produced by acid hydrolysis of many fibrous materials including bagasse and cottonseed hulls.

Table 4. Effects on liveweight gain of cattle supplementing a basal forage/concentrate based diet with soyabean meal or soyabean meal treated with sulfite liquor (SL) at 200°F for 2 hours (Lewis et al 1988).

 LWt gain
No supplement591
+7% soyabean673
+9% soyabean + 10% SL823
+8% soyabean + 5% SL841

Little work has been done with forage proteins, although there are indications that the presence of low levels of tannins in the forage (e.g. leucaena) does afford some protection of its protein.

There is a great need to research methods for protecting the protein of forages, tree leaves, seeds and pods from local resources, as these are the proteins that are potentially available in the pasture areas of the world.

Trees as a Source of Protein and Soluble Nitrogen in the Rangelands

A number of authors have pointed to the small percentage of the total pasture biomass that is actually consumed by grazing animals in the extensive arid and semi-arid rangelands (Ellis and Swift, 1988). Most tropical grasslands are highly leached and their pastures apparently have low potential to provide ruminants with their required nutrients. The point to be stressed is that 10–30% of pasture biomass is often all that is used by grazing animals. Trees, however, can produce considerable amounts of edible biomass. For example, the tree Prosopis juliaflora produces up to 440 kg of edible pods per annum with an average 16% crude protein, (Riveros pers. comm) but the protein is, in all probability, soluble. Compare this with the usable biomass of 250 kg DM from the poor native pastures of South America and the combination of trees and grassland would obviously be a desirable development and synergistic for cattle production.


The research needs are obvious. Local research in centres of cattle density must identify actual or potential protein sources; must then establish mechanisms for harvesting, processing to concentrate the protein if necessary and protect it from rumen degradation. Appropriate means for using both the processed and unprocessed protein/minerals to optimise the efficiency of animal production must be established.


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