Requirements for protein meals for ruminant meat production in developing countries - R. A. Leng

R. A. Leng
Emeritus Professor, University of New England,
Armidale, NSW, Australia.

World meat and milk supplies must be increased considerably in the next 20-50 years if the predicted demand is to be satisfied. Development of the poultry and pig industries is targeted as being the most likely to develop at a rate commensurate with the demand for meat. However, if development of the alcohol industry occurs, to provide for example, oxygenate for inclusion in gasoline, its demand for grain may lead to a shortfall in the monogastric feed industry. This suggests that emphasis should be directed to ruminants, including cattle, sheep and goats that are capable of producing on feeds high in complex carbohydrates not usable in quantity by the monogastric meat producers.

A review of the literature shows that with appropriate supplementation of the abundant crop residues and other fibrous materials fed to ruminants, complex carbohydrates can be used with great efficiency to attain reasonable production levels. Crop residues, feed from wasteland or mature tropical grasses are mostly deficient in nutrients that are critical for the digestion of fibrous carbohydrates and their efficient synthesis. Supplying these nutrients leads to a significant improvement in productivity and when these supplementation strategies are applied together with management to attain high digestibility of the forage, elevated production can be achieved relative to animals fed, for example, on high quality temperate pastures.

Supplementation involves providing minerals and urea to satisfy requirements for efficient digestion by microbes in the rumen, and augmenting the protein supply to the animal through feeding an escape protein meal. Protein meals appear to have differing roles: when fed at low increments the response in growth of cattle is apparently four times greater than similar increments of protein supplements fed above a critical level.

In dairy animals on forage based diets, the response to supplements of protein meals depends on the genetic potential of a cow for milk yield. Cows on mature forage based diets and with high genetic merit will mobilise body reserves to produce milk and the benefits of increasing protein intake is often more apparent in decreasing a live weight loss than a large stimulus in daily milk production. The prevention of live weight loss has large benefits in terms of reduced inter-calving interval and persistency of lactation.

As daily live weight gain increases with increasing levels of supplementation, the feed requirements to produce a fattened animal can be reduced to 20 percent of the feed required to fatten a similar animal without supplements.

The potential for increasing ruminant production from poor quality forage is of the order of five to ten folds without any increase in the demand for forage. To attain such an increase in production there are associated needs. These include supplements to increase the fertility potential of the breeding herd, the elimination of waste (death of animals) and the provision of incentives for farmers to take up recommended strategies. The latter requires the establishment of an infrastructure for slaughter, distribution and marketing of meat at equitable prices

INTRODUCTION

In the near future, it is predicted that there will be a greatly increased and continuing demand for protein foods for human consumption in most developing countries, and particularly in Asia. (Delgado, et al. 1999).

Purchasing power often limits the amount of meat and milk consumed by people and as disposable income increases, people tend to consume more of these commodities. At the same time there is an enormous moral need to provide protein in deficient diets of resource-poor people who do not have the capacity to purchase meat or milk on a regular basis.

Protein under-nutrition or malnutrition in the early life of humans may lead to small stature and developmental retardation (Waterlow, 1998) and in recent years it has been recognised that a balanced diet supports an efficient immune system and promotes resistance to parasites and disease, even into adult life.

Rice, the staple food (calories) of much of Asia has the lowest average protein content of all cereal grains (6 percent crude protein [CP]). In the polished grain form in which it is mostly consumed, it is also the least nutritious of the traditional staples. Most countries are however, self sufficient in staple foods. The desirable development for future food production, from a welfare viewpoint, would seem therefore to be in emphasizing meat production to meet the demand for protein that accompanies increased family incomes and education. This in turn results in increased awareness, mainly by women, of the benefits to the family and to young children in particular, of balanced diets.

The options for increasing meat production are many and depend on:

• the country;

• availability of feed resources;

• the presence of infrastructure for slaughter;

• the distribution and marketing of products;

• the endemic diseases of livestock;

• the climate;

• Socio-economic factors, such as the religious taboos against consumption of pig meat.

In overall terms the major issues that determine meat supply and availability are:

1. which species is best supported by the available resources:

i. pig?
ii.poultry?
iii.ruminants?

2.Which production system is appropriate to the country:

i. industrial scale?
ii. backyard systems?
iii. or combinations of the two that suit the particular country?

The increased demand for meat in developing countries is a direct result of the increasing middle class that insists on a balanced diet and recognises the good eating value of meat. This greater demand has been used to suggest that greater emphasis must be directed to production of poultry in Muslim countries, and pig and poultry in countries where pig meat is acceptable. This does not eliminate other developments but places emphasis on replication in the developing countries, of the industrial methods currently being used in most developed countries.

FEED GRAIN COST AND AVAILABILITY IN THE FUTURE

Industrial livestock production in Western countries has been supported and encouraged by the availability of inexpensive grain, and the opportunity provided by the size of production units to minimise the number of relatively costly workers. As a generalization, grain has been comparatively inexpensive as a feed resource in industrialised countries for many reasons including widespread subsidization.

Access of producers to affordable feed grain is a pivotal requirement for development of industrial scale pig, poultry and beef production in the countries with emerging economies. The development of range or scavenging systems for poultry production is also assisted by inexpensive grain that is often fed as a supplement. Diet components often have to be imported; for example, approximately 80 percent of concentrates have to be imported into countries such as Bangladesh to raise poultry under intensive and modified backyard production systems. The scavenging systems however, are not necessarily dependent on grain availability and there are a number of opportunities for providing alternative sources of feed.

In a number of developing countries, the village chicken producers are mostly women that have access to small loans for this purpose, and the family benefits in two ways:

• The increased income that results from raising poultry.

• The ability of the women poultry producers, with their improved income, to siphon off a proportion of their production for the family, increasing the protein intake of young children in particular and at a cost equal to that of production.

Where labour costs are low, the majority of the costs of production of industrial pig and poultry reside in the cost of feed. Relative to average income, chicken and pig meats produced in ‘modern systems’ are mostly unaffordable for a large proportion of the urban and rural poor. Nevertheless, the increasing pressure for meat production to meet the demand of the urban middle class will see village and industrial scale production systems increase in developing countries, providing feed costs are kept under control.

Many arguments can be made against the use of grain for livestock production based on concerns for the environment, soil fertility, erosion and salination and socio economic questions. In marketing grain, the high costs of land degradation in some areas has not been factored into prices. Grain production is inextricably linked to fossil fuel inputs through the use of water, fertilizers, pesticides and fungicides and the need for tractors. As such, grain prices will be dependent on inexpensive fuel. Many of these factors have been discussed by Delgado et al. (1999) and are not developed further here.

If grain prices rise substantially, then smallholder livestock raising on locally available resources with recycling of wastes, has the potential to become the most environmentally sustainable of all major farming systems world wide. There is obviously an enormous number of factors involved in such an evolution (revolution) that would need to be addressed and the concept is not taken further here, except to suggest that in the future, pressures that have not so far applied, may have substantial effects on the availability and price of feed grain.

ALCOHOL PRODUCTION FROM GRAIN AND GRAIN AVAILABILITY

World grain availability has been affected in the past, mostly by the demand for food for humans and feed for livestock. Grain for livestock will have to compete with increasing demand for grain to produce industrial alcohol. The latter arises from the demand for industrial alcohol as an oxygenate to add to gasoline for use in automobiles.

The oxygenate in gasoline is required to lower the levels of many compounds in motor vehicle exhaust gases that pollute the atmosphere of high population density cities, such as Los Angeles. In 1999 legislation was introduced in the United States to enforce the addition of oxygenates into gasoline to more completely remove ozone, carbon monoxide, particulate matter and oxides of nitrogen as well as potential carcinogens such as benzene and 1,3 butadiene found in car exhaust emissions.

A compound derived in the fractionation of oil (methyl tertiary-butyl ether, [MTBE]) was first used for this purpose. Because of its affinity with water, MTBE polluted the ground water sufficiently to create alarm, gave water a pungent odour and made it undrinkable The extent of contamination of ground water led to its replacement by alcohol, which is higher in oxygen and produces no pollutants when co-combusted with gasoline. Industrial production of alcohol for these purposes is predicted to increase to a minimum of 23 billion litres annually within 3 years and utilize over 70 million m³ of maize (Figure 1). This is 21 percent of current production in the United States and would potentially remove the world surplus of grain (Pearse Lyons and Bannerman, 2001).

Figure 1. Past and future use of grain for industrial alcohol production in the United States to meet the requirements for the inclusion rate of alcohol into automobile fuel (Pearse Lyons and Bannerman, 2001; Renewable Fuels Association, 2001).

California, the potentially largest market for industrial alcohol as an additive to gasoline in the United States, needs to produce between 2.7 and 3.2 billion litres of alcohol annually. In response to this, it is considering the future development of industries for production of alcohol from biomass (California Energy Commission, 1999).

A huge demand for grain, or the transfer of land into production of other potential feedstock for alcohol production such as sugar cane, may result in a world scarcity of grain. It will be remarkable if this increased market demand does not increase the price of grain on international markets. If this is the case, then any grain dependent animal production must necessarily become relatively more expensive. Thus, such developments are certainly unlikely to benefit the poor, other than providing cash through the jobs that may be generated. Even these will be minimal if industrialized farming is promoted at the expensive of small farmer operations. It is likely that a reliance on industrial sized development will actually reduce employment because of the economies of scale required; and the demise of the small producer is predictable where these strategies are adopted.

POTENTIAL SPIN-OFF BENEFITS FROM DEVELOPMENT OF AN ALCOHOL INDUSTRY BASED ON GRAIN

The production of alcohol from grain yields a by-product that is low in carbohydrate but high in protein and fibre, namely gluten meal (where isolated starch is the feed stock) or spent distillers grains (where ground cereal grains including maize are the feed stock). This is highly suitable as a supplement for ruminant animals, particularly those dependent on poor quality feeds such as crop residues (see below) the consensus is that these by-product meals are high in escape protein that can be used directly as an amino acid source by ruminants. The yield ratio of protein meal to maize grain fermented is roughly 300 kg protein meal/ton of grain, with about 410 litres of alcohol output.

THE FUTURE ROLE OF RUMINANTS IN MEAT PRODUCTION IN DEVELOPING COUNTRIES

Undoubtedly, industrial poultry/pig production delivers the high quality meat with good eating value that the middle class demands. There is, however, a clear moral issue for any agency to direct development so that the resource poor may share in the outcomes, whether it is from increased income or nutrition, or both. It is also unwise to ‘put all your eggs in the one basket’ of industrialized production, when there is a massively under-utilized resource of ruminant animals in most developing countries that are producing at a fraction of their potential. The low level of production of large ruminants results from a number of factors, such as:

• the fact that their major feed resources are poor quality crop by-products and are not supplemented to overcome their deficiencies;

• they are mainly kept as an insurance against disasters when they can be sold to provide cash;

• they are mainly kept for work or religious purposes.

In all cases, efficient production is not necessarily a priority as it has little impact on the animal’s value.

Meat from ruminants can be produced inexpensively from low cost (low quality?) forage by efficiently harnessing the animal’s fermentative digestive systems. Cattle, buffaloes, sheep and goats can be produced on smallholder farms from waste forage (often regarded as a free resource) that is dispersed widely and does not therefore easily meet the requirements of intensive systems. These low cost production systems are not dependent on large volumes of carbohydrate or protein that are directly usable by either the human population or in pig and poultry production.

Over the past 20 years, ruminant nutrition has developed to the extent that efficient production of meat and milk (also wool and hair) is possible from forage such as the crop and agro-industrial by-products and biomass from fallow and waste land. Ruminant production from these products provides a major hope for meeting the demand for large quantities of medium to high quality protein for human consumption at relatively low cost. This is not a new concept and the efficiency and level of ruminant production that is achievable on such diets has been debated for a number of years (Preston and Leng, 1986). Development of such production systems provides major opportunities for upgrading many smallholder farming and agroforestry systems in large areas of Asia and for increasing many fold, the income of small and even landless farmers.

Using crop residues for ruminant productivity

Crop residues, agro-industrial by-products, weeds/grasses from waste and fallow cropping land, foliage of trees and shrubs and forage/tree crops and foliage produced as an intercrop are the basal feed resources of ruminants in developing countries. Crop residues such as straw are by far the greatest available biomass.

Straw is considered by most scientists to have little nutritional value because of its low metabolizable energy (ME) that is predicted to support little more than the maintenance of ruminant animals. Uninformed farmers regard it as a poor feed because cattle generally loose weight when it is fed without supplementation

In 1990, Leng (1990) challenged the description of crop residues as being of low quality and preferred to describe them as imbalanced forage. The point was made that with small additions of supplementary nutrients to forage, a large response in animal production could be achieved. These improvements with appropriate low-level supplementation cannot be predicted from the ME content of the mixed diet.

The concepts that were developed are more applicable in developing countries, for example in India, to increasing milk yield in cows fed high forage diets (NDDB records, [FAO, 1997b]). Industrialized countries normally have little or no dependency on poor quality forage for ruminant industries, except perhaps where there are large landmasses mainly suitable for the production of grazing ruminants.

Poppi and McLennan (1995) concluded though, that large increases in productivity through small additions of protein meals were not attainable in cattle on low quality forage. However, as will be discussed below, there was a small error in the analysis of results from cattle growth trials. These disguised important aspects of the response of ruminants on low quality forage diets to supplements. A re-examination of the available data from feeding trials of this nature in various countries suggests that such an error has major implications in terms of the potential of these abundant resources for highly efficiently ruminant production. The examples will be drawn from growth trials with cattle, but the general conclusions are applicable to other species of ruminant.

CHEMICAL COMPOSITION OF CROP RESIDUES AND THE NEED FOR SUPPLEMENTS WHEN FED TO RUMINANTS

Mature, dried foliage and stems of grasses, are normally low in protein (less than 3 percent CP) and have been variably leached of soluble components, including minerals, proteins, sugar and starchy carbohydrates. Mature dry forage, is therefore mostly complex or structural carbohydrate intermingled with the plant’s cement, lignin. The content of soluble materials will vary and at times is critical because it can change the overall digestibility of forage by up to 10 units. The content may also reduce the need for supplemental minerals and urea, which are needed for its efficient fermentative digestion. Thus managing the harvest of forage is critical to ensure its potential feed quality.

SUPPLEMENTATION REQUIREMENTS FOR OPTIMUM USE OF LOW DIGESTIBILITY FORAGE BY RUMINANTS

For efficient digestion of forage, irrespective of its solubles content, the microbes in the rumen require a source of ammonia and a medium, which is balanced with minerals. Once these are provided, the extent of digestion is only limited by the structural nature of the plant fibre and the degree to which this fibre is embedded in or surrounded by lignin.

Ruminant nutritionists have established which nutrients are essential for microbial growth in the rumen and efficient methods are available to ensure that no mineral or ammonia deficiencies occur in animals feeding on mature forage diets (e.g., provision of multinutrient blocks [IAEA, 1991]). Supplementation of the animal feed to ensure an efficient digestion of forage in the rumen usually improves digestibility and intake and increases productivity. This is the first step in combating low productivity when cattle are fed on forage (Leng, 1984).

Improving protein nutrition is the second strategy for increasing production in ruminants with a high protein requirement. These include young animals following weaning, cows in the last trimester of pregnancy and also lactating cows. Here the question arises, for immature animals on poor quality forage, as to the extent that growth can be increased by providing nutrients for the rumen and extra protein for absorption?

The provision of more protein for absorption in a ruminant on a straw-based diet can be achieved by a number of methods that include:

• Ensuring no microbial growth factors are deficient in the diet and microbial growth is optimised.

• Providing a protein meal that is relatively slowly degraded by microbial action in the rumen and from which a proportion of dietary protein enters the intestines for digestion (termed escape protein).

• Manipulation of the microbial ecosystem to minimise inefficiencies brought about by protozoa that prey on bacteria and reduce protein flow to the intestines (defaunation/oil drenching).

A discussion of various factors involved in the amounts of microbial protein entering the intestines, or the extent to which a protein meal escapes to the lower gut is not warranted here (see Preston and Leng, 1986 for a discussion of these factors in ruminants fed on mature forage).

In practice, escape protein for supplementing ruminant diets is sourced from oilseed meals, in particular cottonseed meal (solvent extracted), hulled cotton cake (pressure extracted), copra meal, gluten meal or soybean meal. Numerous experiments have been done in various areas of the world to evaluate strategies of supplementation to increase the growth of cattle, and the efficiency of using mature forage from dry season pasture and crop by-products.

PRACTICAL ASPECTS OF THE USE OF SUPPLEMENTATION STRATEGIES TO ALLEVIATE LOW PRODUCTION IN CATTLE GIVEN LOW DIGESTIBILITY FORAGE

What to supplement and how much to give and the likely response in growth of young cattle are major economic considerations for livestock production from mature forage, which is the staple of most ruminants in developing countries. For example, the forage feed to large ruminants in Bangladesh comes approximately 50:50 from rice straw and forage gathered from wastelands or fallow. In Asia, despite a potentially large shortfall in forage requirements for animal feed, a considerable amount of the annual straw crop is either wasted or used for purposes other than livestock feeding.

Benefits of providing protein supplements to cattle consuming poor quality forage

Mature forage from grasses such as cereal and pasture, have an ME content rarely more than 5 MJ ME/kg dry matter. The requirement tables predict that such feed will probably maintain young animals, providing nitrogen and mineral deficiencies are corrected.

The idea that straw is too low in ME to support growth often leads to a recommendation to replace it with a more energy-dense feed and/or increase the ME content by treating it with an alkali such as ammonia. Treatment with urea or ammonia to increase straw digestibility is a highly recommended procedure, as it increases the use of the basal low cost resource. In addition, it also corrects N deficiency in the rumen. The increased digestibility of straw consumed often increases growth of cattle by up to 300 g/day. The value of this additional growth is often less than the cost of treatment (see FAO, 1997). This would suggest that a cereal grain should be fed to enhance the intake of energy, even where there is considerable biomass available. From published results, however, it appears that the productivity of ruminants is limited by the balance of nutrients derived from digestion in the rumen. By providing more protein for digestion in the intestines through supplementation with an escape protein source, the overall efficiency of use of absorbed nutrients is improved. The more efficient use of the ration results from the closer balance of nutrients absorbed to the nutrients required, and to a greater intake of basal feed and thus total nutrients.

This concept has been challenged. Poppi & McLennan (1995) concluded that the benefit of supplementation of low protein feedstuffs for ruminants is largely an effect of the increased nutrients supplied (ME). The same authors also concluded that the ME of straw underestimates production levels because the amount of forage that can be consumed by ruminants is much higher than has previously been reported. This is too simple because the measurement of ME per kg of forage (M/D) is used to predict production without reference to feed intake. In most situations ME is predicted from an in vitro digestibility measurement with obvious associated errors.

Response to escape protein of young ruminants given low digestibility forage

Credit for the discovery of the need for escape protein in the diets of producing ruminants is difficult to assign, as it slowly evolved from basic observations when ruminant nutrition was in its infancy.

The need for escape protein by young cattle to achieve high growth rates was most clearly demonstrated in feeding trials with high energy, low protein, non-conventional feeds such as liquid molasses. Preston and Willis (1974) demonstrated that replacement of urea with fishmeal in a diet for young cattle based on molasses, had marked stimulatory effects on growth and most importantly, on efficiency of feed utilization.

Even on high quality grain based diets fed to lambs, where part of the protein in grain is likely to escape digestion in the rumen, Ørskov et al. (1973) showed that providing fishmeal in a way that caused it to bypass the rumen, stimulated growth of lambs. Thus, fish meal would appear to have created the conditions for greater capture of some of the grain protein lost from the rumen, giving an increased efficiency of feed utilization, even when cereal grain intake was optimized (Table 1).

Numerous publications have shown that cattle growth rate on straw based diets could be stimulated by increasing supplementation with a protein meal (see for reviews Preston and Leng, 1986; FAO, 1997; Leng, 1990).

TABLE 1
Live-weight gain and efficiency of feed utilization by lambs fed pelleted, crushed grain (containing urea and minerals) supplemented with additional urea in the pellet, or fishmeal artificially made to bypass the rumen (after Ørskov et al., 1973).

* By allowing the animal to suck on a bottle of fishmeal mixed with water, the oesophageal groove reflex was preserved and the rumen bypassed.

Research on the mode of action of supplements on the growth of young cattle is difficult to rationalize. In some studies the escape protein supplement was found to stimulate forage intake whereas in other studies with young cattle, forage intake was unchanged or reduced. The studies where straw intake by cattle was stimulated when supplemented with escape protein were usually undertaken in hot climates. This suggested that forage intake of ruminants may be lower on mature forages such as straw, at times when humidity and environmental temperature induce an intolerable thermal load on the animal, and that supplementation with escape protein maybe much more effective in alleviating low productivity in ruminants in hot climates (Leng, 1990).

Energy versus protein supplements to improve the growth rates of cattle fed on poor quality forage

Fermentative digestion in the rumen, when uncompromised by deficiencies of nutrients, converts feed components into volatile organic fatty acids (VFA) and microbial cells (that are 40-60 percent protein) in a fairly constant ratio. Therefore on diets where rumen microbial growth is optimized, it is difficult to alter the protein to energy ratio in the nutrients absorbed by feeding supplements that are digested in the rumen. In other words there is no such thing as an energy supplement for ruminants.

Only if supplements are degraded by microbial action in the rumen, at a rate that allows some to leave in the digesta to the lower tract, do they increase the balance of protein to VFA nutrients absorbed. Protein (amino acids) relative to energy in the nutrients absorbed may be altered by supplementing with a meal high in protein that has:

• a structure relatively resistant to microbial attack

• or been protected from microbial action by chemical or physical treatments or

• in mastication, comes in contact with materials that protect it from microbial action (this often occurs when secondary plant compounds are present in high concentrations).

Degradable protein, as compared to an equal weight of fermentable carbohydrate, produces a lower yield of microbial cells with a higher amount of VFA. The reason for this is that there are less high energy phosphate bonds available to microbes when protein is converted to VFA and ammonia than when carbohydrate is fermented to VFA. Thus cell yields on protein substrate are about half that on carbohydrate.

Examples of protein meals that are relatively resistant to rumen microbial degradation and provide protected or escape protein when fed to ruminants include those that:

• have been chemically processed with formaldehyde or xylose (treated vegetable protein meals e.g. xylose-treated soybean meal);

• have been through heat treatment in solvent or pressure extraction processes for oil (e.g. cottonseed meal, cotton cake and copra meal);

• are associated with relatively low levels of secondary plant compounds that bind proteins (e.g. some leaf protein in tree foliages and some vegetable protein meals);

• have a high degree of sulphur amino acids with considerable cross linkage in the amino acid chains (e.g. gluten meal and dried distillers waste from grains).

South African fishmeal is possibly the best form of bypass protein and is usually flame dried and treated with formaldehyde to prevent decomposition (see for response in cattle Silva et al., 1989). Cottonseed meal appears to be one of the better protected vegetable protein meals, possibly combining protection from heat treatment and protection by secondary plant compounds.

The benefits of feeding supplements to young cattle on poor quality forage diets, where the supplements are regarded as an energy source (barley or sorghum) or a source of extra protein at the intestines (cottonseed meal [CSM]), are shown in Figure 2.

At the higher level of supplementation of cattle shown in Figure 2, the ‘supplement’ becomes the major dietary source of ME. In practice, a supplement, which is usually considerably more expensive then the basal feed, should rarely be fed at above 0.5 percent of the animal’s live weight. This requires emphasis because in cattle fed mature forage, the efficiency of conversion of the supplement to live weight gain, with increasing amounts of cottonseed meal, is some four times greater as the increments are increased progressively to 0.5 percent of live weight, as compared to the efficiency of conversion above this level (see Figure 3). For economic evaluation, it is important to define the early part of the response curve to supplements of protein meals in young cattle on poor quality forage (see Dolberg and Finlayson, 1995).

Supplementation strategies for young cattle on low quality forage

Many experiments have demonstrated the benefits of supplementing protein meals to ruminants fed poor quality forage. Most have recognized the need to provide for an efficient working of the rumen by including minerals and urea in the diet. However, only some of the experiments included sufficient levels of protein meals to provide response relationships for both predictive purposes and economic evaluation. The exceptions are in research reported by Elliott and O’Donovan (1971), FAO, (1983) Saadulah, (1984), Wannapat et al., (1986), Perdoc, (1987), Zhang Weixian et al., (1994), Finlayson et al., (1994), Dolberg and Finlayson, (1995), McLennan et al., (1995). However, in some of the feeding trials there was no control group fed only the basal diet and unfortunately therefore the data from these particular trials cannot be incorporated in the analysis below.

Figure 2. The supplementation of a low quality pasture hay with cottonseed meal, barley or sorghum grain. Young cattle were given a poor quality pasture hay and minerals and then given graded amounts of the various supplements according to their live weight. (McLennan et al., 1995)

Where a large number of results from research conducted at different sites can be drawn together, some very useful generalizations can be developed and used as ‘rules of thumb’ and as guides to the likely economics of developing cattle fattening on straw. This is an alternative approach to using ME content of the available feeds to design diets for ruminants.

The results of a number of studies of the live weight response of cattle on low quality forage or at pasture during the dry season, to supplements of protein meals are shown in Figures 3a-3d. A number of equations have been fitted to the data which have been collated mostly by Poppi and McLennan (1995) and include results from McLennan (1995), Smith and Warren (1986a,b), Hennessey et al., (1983), Karges et al., (1992).

To take out some of the variability of weight of animals used in the different experiments and differences in protein meal quality, the intake of supplement is expressed in g of crude protein intake per kg live weight (LWt) per day (gCP/kg LWt/d), and the response is calculated as the increase in live weight gain (kg/d) over that of un-supplemented control animals. The data, originally compiled by Poppi and McLennan (1995) have been combined with more records from trials where straw has been the major feed resource, as indicated in the references listed above.

Figure 3a. The data are fitted to a linear regression with an intercept as suggested by Poppi and McLennan (1995) or through the origin

Figure 3b. A polynomial fit through the origin. This is unacceptable as there is a down turn in the benefits of supplementation at high rates which is biologically incorrect

Figure 3c. The potential to describe the results as two distinct sets of data described by independent linear regressions. These regressions are intended to provide prediction equations that are relatively easily understood.

Figure 3d. The most appropriate description is probably the logarithmic linear relationship shown above

An oversight by these authors is apparent in their original analyses, as they fitted a linear regression to the data despite having already corrected it for the live weight change of the control, un-supplemented group. This disguised the initial and higher response to feeding protein supplements to young cattle on these feeds. Figure 3a shows the relationships as fitted by Poppi and McLennan (1995) and that forced through the origin. The latter is a very poor fit to the data (R²=0.22) as compared to the former (R²=0.74).

A polynomial appears to more accurately describe the response but seems to make an underestimation at extremely high levels of protein meal inclusion in the diet. On the other hand, a logarithmic relationship appears to best describe the data with the highest amount of the variability taken out by the regression (see Figures 3b and 3d).

A further argument to use two independent relationships is the plausibility that a protein meal supplement fed to cattle may have differing roles at low compared to higher levels of inclusion in a forage diet. In practice it is also likely that the rate of supplementation will be restricted to low inputs for economic reasons. It is suggested that the most logical approach for this to be used as a guide for farmers, is to represent the data as two linear response relationships, as shown in Figure 3c. The different responses may be attributed to:

• an initial effect of an increased protein supply and a more balanced array of nutrients for efficient live weight gain (the response in a 200 kg steer is 1.2 g gain/1 g cottonseed meal consumed) and

• the fact that higher intakes of protein meal supplement cause a lower rate of response per unit of additional supplement due to the fermentation of a part of the supplemented meal. In the case of a higher level of protein meal supplement, the protein to energy ratio is higher than when less forage is replaced with protein meal supplement.

The important issue is that at low supplementation rates (i.e. the early part of the response curve) the returns in live weight gain are approximately four times greater than at higher levels of supplementation (i.e. in the later part of the response curve).

Summary of growth trials with young cattle on mature forage supplemented with protein meals

In summary, the effect of supplementing young cattle (200 kg live weight [LW]) grazing dry pasture or straw with an escape protein meal such as cottonseed is:

• at up to 0.7 kg/day supplementation with cottonseed meal, the response in live weight gain would be approximately 0.84 kg/day or a conversion efficiency of supplement to live weight gain of 1.2 g LWt/g;

• above 0.7 kg/day the improvement is approximately 0.35 g LWt gain/g.

Thus, small inputs of a bypass protein have a ‘catalytic’ effect on the utilization of a low quality forage, but the level of production that can be achieved depends on the ‘actual quality’ of the forage. From the literature some generalizations can be drawn:

• straw diets fortified with urea and minerals and fed to cattle support live weight changes from minus 200 to plus 100 g/head/day;

• straw treated with balanced nutrients for the rumen organisms support growth rates that may vary from about maintenance to around 300 g/head/day.

The greater the digestibility of a forage the higher the intake and the higher the growth rate without supplementation (see for discussion FAO, 1997).

In most situations the growth rates of cattle fed on treated straw compared with untreated straw are not economically attractive, unless production levels are boosted with supplements which reduce the time to market and the total feed requirement.

Digestibility of a basal straw diet by cattle supplemented with urea/minerals depends on a wide

• number of factors including:

• cereal variety;

• soil fertility;

• climatic conditions, particularly those between harvest of grain and storage of straw;

• storage conditions;

• method of drying prior to storage, particularly for wet season rice straw;

• other forages mixed with the straw including higher digestibility grasses.

Other large effects on the feed quality of straw include the timing of harvest and drying and storage processes. Essentially, a major loss of soluble nutrients can occur in pre and post harvest management, and to maximize the value of straw it is essential that these losses are minimized.

Dolberg and Finlayson (1995) reported on studies undertaken in two Chinese provinces within an aid project, to introduce the use of urea ensiled or ammoniated wheat straw as a basal diet for fattening cattle (Figure 4). The available protein source was cottonseed cake and response curves were developed showing the live weight gain of young cattle when fed at different levels of supplementation. These studies are included in Figure 3, but despite a higher growth rate of cattle on the basal feed resource in Henan province, there was a much higher stimulation of live weight gain in the lower levels of supplementation in the animals in Hebei province. However, as supplementation in Hebei increased above the level where the catalytic response ceases (about 0.7 kg cotton seed cake/day) the responses were approximately the same per unit of cottonseed meal consumed.

It appears that the catalytic response in growth of young cattle to low inputs of protein meals in Henan province was not observed because supplementation rates were always above the cut off in the catalytic level of supplementation. Similar effects were also apparent during studies in Thailand, where young cattle were fed ammoniated straw with supplements, but unfortunately there were no cattle without supplementation in the reported trial (Wanapat et al., 1986).

Figure 4. The response of Yellow cattle given urea ensiled wheat straw (Hebie province) or ammoniated wheat straw (Henan province) as a basal diet, to increasing levels of supplementation with cottonseed meal (after Dolberg and Finlayson, 1995)

IMPLICATIONS FOR FUTURE MEAT PRODUCTION

Production of meat and milk is influenced by both the reproductive efficiency of the herd and the production levels achieved by the cattle being fattened. A generalized statement based on experience in a large part of south East Asia indicates that cows maintained by small farmers that rely on the locally available forage and are not strategically supplemented, probably have their first calf at 4-5 years of age and produce a calf thereafter at intervals of a minimum of 2 years.

Under the harsh conditions, a high proportion of the calves die soon after birth and many cows barely replace themselves within their lifetime.

The cow’s maintenance is often justified in order to provide replacements for working bullocks and so that the cow can stand in when a working bullock is incapacitated at a critical time in crop production operations. This can act as an insurance against crop failure. The cow also produces small amounts of milk for its calf and the family. However, sharing of the milk and/or early weaning causes calves not to thrive and often leads to their early death.

The supplementation strategies discussed above can (could) have remarkable effects. Better feeding management increases the growth of young animals, and reduces their breeding age to 2 years. In older animals, the maintenance of live weight by the same approach can reduce inter-calving interval to 1-1.5 years. The overall improvement in animal health and body condition is accompanied by increased survival of young animals prior to weaning and reduced death rate among cows at calving. The effects on reproductive efficiency alone can more than double the availability of young animals for fattening.

In India, a major benefit of the introduction of multi-nutrient block and bypass protein supplementation of lactating cows in the Cooperative Milk Unions (under the auspices of the National Dairy Development Programme), was attributable to improved reproductive efficiency of the supplemented cows. This led to a greater number of cows in milk at any one time and an improvement in both lactation length and daily milk yield (Leng and Kunju, 1990).

Ruminant production and forage availability

Improved reproductive function leads to increased mouths to feed and immediately the objection is made ‘where is the extra feed to come from?’

The point that needs stressing here is that the amount of feed needed to finish an animal is related to its growth rate. The higher the growth rate the lower the feed requirements per unit of live weight produced.The clearest indication of this comes from research in China (Table 2) which showed that if the necessary supplements were added to the existing amount of forage, it was possible to achieve a 10-13 fold increase in meat from ruminants. Depending on the cost of the protein meal, the most economic response is likely to be at low protein inputs, where production from a unit of straw may provide a 5-6 fold increase. The conversion of concentrate into live weight gain in ruminants is far ahead of that of pigs and poultry, providing the supplementation levels allow the catalytic response, which occurs at less than 1kg of protein concentrate per day.

Responses to escape protein in dairy cows

The response to protein intake by dairy cows fed on forage has not been so well defined as for young growing cattle. However, in milking cows on a basal feed of mature forage, supplementation with high protein meals has a major effect on live weight, often reducing weight loss in lactation. As there is a high correlation between live weight and the ability of lactating cows to breed, supplementation with protein meals during lactation often reduces the time to first oestrus reduces inter-calving interval and improves the overall reproductive efficiency.

TABLE 2
The potential of balanced supplementation to increase meat production from young cattle fed low quality crop residues treated to increase digestibility. The calculations are based on the data from Dolberg and Finlayson (1995). The growth rates of the cattle were accurately predicted from the regression shown in Figure 3d

The major effect of supplying escape protein compared with traditional concentrates to dairy cows being fed mature forage, appears to be to reduce the cow’s need to draw on body reserves to maintain milk production. Supportive evidence for this is shown in the data given in Figure 5 and Table 3.

Higher genetic potential for milk production is linked to the ability of the good (high yielding) cow to mobilize body reserves, as against a poor cow that does not have this capacity. Therefore the benefits of supplementing cows with a high genetic potential for milk production is more effective in reducing inter-calving interval than it is for those having a poor potential.

Definition of the amount of escape protein needed to attain the point at which the change of roles of the protein meal supplement occurs is clearly needed in lactating cows.

Figure 5. The effect of feeding sorghum or copra meal (both at 3 kg/day) to dairy cows on pasture. Supplementation with protein seems to be more beneficial in reducing body weight loss (kg in 12 weeks) in dairy cows than in promoting milk yield (kg/day), which is only stimulated to a minor extent (Ehrlich et al., 1990)

The concept is that the initial supplement protein source needs to be highly protected from microbial action for maximum efficiency, but after this response is achieved, a partially protected protein meal appears to be most effective. This is because the requirements for amino acids compared with other nutrients appear to be closely balanced with additional production from such a source. Perhaps in this case there is good synchrony of nutrient supply (carbohydrate ammonia and minerals) from the feed for its optimal fermentation in the rumen.

TABLE 3
Effects of replacing balanced concentrates (20 percent CP) with a concentrate high in escape protein (30 percent CP) on the live weight change and milk yield of Jersey X Kankrej cows (after Leng and Kunju, 1990). Note that the balanced concentrate was given at about half the rate of the protein concentrate

Minimising the need for escape protein

The definition of the growth response curves for feeding protein meals in a diet of straw given to cattle may be used to predict their growth rates and from economics analyses, establish priorities for the ruminant industries.

Research to minimise protein meal requirements is a priority since these are usually expensive and often in short supply. The most appropriate way would seem to be to more completely protect the protein in a meal (for example cottonseed meal protein is estimated to be between 40 and 60 percent protected) to maximise the initial response and then to feed untreated meal for the most economic level of production.

One way of partially reducing the initially high requirement for escape protein in cattle on forage diets is to increase the net flow of bacterial cells to the lower tract by removing the predatory protozoa from the rumen (defaunation). Bird and Leng (1978) first showed that defaunation of the rumen improved the growth of cattle on low protein diets (see Figure 6). Wool growth response in sheep to defaunation indicated that more protein was delivered from the rumen of fauna free as compared to normal sheep (Bird et al., 1979). This was confirmed by Veira et al., (1984) who demonstrated that introducing protozoa into the rumen of sheep that had previously been without them, reduced microbial protein flowing to the intestines. The work of Ushida et al., (1984) indicated that in the absence of rumen protozoa, more dietary protein, in addition to bacterial protein, moved to the lower tract in sheep. The consensus would appear to be that protozoa in the rumen reduce total protein flow to the intestines and therefore lower the protein availability from the feed consumed by ruminants.

There is thus potential to minimise protein requirements of ruminants on low protein diets by manipulation of the rumen to exclude and maintain the animal free of protozoa. Until recently, no methods have been discovered that can be easily applied to existing farming systems.

Nguyen Thi Hong Nhan et al., (2001) working in Vietnam showed that treating young cattle fed on rice straw with an oil drench, increased their subsequent growth rate. For the first 20 days after drenching, the rumen appeared to be free of protozoa and the response was attributed to their absence. (Figure 7). Subsequent studies by Mom Seng et al., (2001) showed that rumen protozoa appeared to be eliminated initially but returned within two weeks with a changed population mix.

The very large protozoa that usually make up a small proportion of the numbers but are often a large proportion of the total biomass, returned to only a fraction of their population density pre-drench. A slow recovery of these large protozoa has been previously observed, where fauna free sheep were naturally infected when they returned to a flock of normal grazing sheep (Hegerty et al., 2000).

Figure 6. The effects of the defaunated state on growth of cattle fed straw/urea/molasses based diets supplemented with sub-optimal levels of escape protein meals (Bird and Leng, 1979)

The amount of polished rice (15 percent CP) that had to be fed to get the same response as drenching once with oil, was about 0.5 kg/day.

CONCLUSIONS

It is argued in the paper by Delgado et al., (1999) that the relative price of grain will not rised significantly in the next 50 years, and that grain surplus to human requirements can be used to provide the basis for an expanding industrialized pig and poultry industry in developing countries to meet the growing demand for meat.

Legislation for the inclusion of alcohol (an oxygenate) in gasoline for motor vehicles in order to lessen the hazards of chemical smog in major cities of the United States, is likely to have a major impact on the economics of feed grain. The production of alcohol is set to monopolise surplus United States’ maize grain by 2005. Whilst this will have repercussions for livestock industries in all parts of the world, a major benefit will be the considerable quantities of fibrous high protein by-products that will become available, and are most suited to supplementation of ruminants being fed on low digestibility forage.

It seems likely that the development of alcohol industries will also be implemented in a number of countries, increasing the use of starch and sugar based crops for this purpose. In the future there will also be considerable effort to use biomass (urban, forest and agricultural waste) for the same purpose, but the technology has yet to be refined to support economic production (California Energy Commission, 1999).

Figure 7. The effects of a single oil drench at the beginning of the fattening period on the growth rate of young cattle fed rice straw and supplements.

Young cattle were given rice straw with grass (RS) or rice straw/grass with a supplement of 1kg/day of polished rice (RS+RP). One group in each feeding system was drenched with 5 ml vegetable oil/kg live weight (+oil) at the beginning of the feeding trial

Source: Nguyen Thi Hong Nhan et al., 2001

A world shortfall in feed grain will adversely affect intensive animal production industries and limit the production of meat.

It appears that the development of ruminant industries has the potential to meet any short fall in meat, as the feed base of cellulose biomass is abundantly available and inefficiently utilized at present. The use of poor quality forage, un-supplemented for ruminant production, is realising less than 20 percent of its potential. It is relatively easy to provide the technology to make more than a five fold increase in meat production from poor quality forage without finding new sources of basal feeds. However, it will be necessary to identify and prioritise the protein meals that are required as supplements to increase the efficiency of production to levels that are economic.

Protein concentrates may be more efficiently used for meat (and milk) production from ruminants when combined with forage from such sources as crop residues, which in many developing countries are regarded as a free resource.

The widespread distribution of ruminants in general, and cattle in particular, among rural farms where the forage is a by-product of crop production, is highly advantageous. However, to be successful in encouraging the development of such dispersed, small production units, the necessary supplements must be made available. Suitable slaughtering facilities and an equitable marketing system are also essential elements.

These requirements are well demonstrated by the success of the Milk Cooperatives in India. These have shown that dispersed systems for milk production from indigenous cows or their crossbreeds, together with local feed resources, can be highly viable economically where the necessary supplements are made available, and where there is a guaranteed, equitable and wealthy market concentrated in a nearby city.

Small farm systems appear to be best operated outside any industrial framework, which then ensures that the farmer benefits directly as against indirectly, as is the case with workers in industrial enterprises. The marketing of supplements (multi-nutrient mineral urea mixes and concentrates high in escape protein), provision of slaughter houses and packaging plants and a guaranteed market, together with some form of time payment to ensure a regular income, are all considerations for the introduction and success of such a development.

The overall development could realise the potential of a five fold or more increase in meat production, particularly in those developing countries with vast areas of crops.

Reports indicating that relatively high levels of meat production are possible on these crop resources have often been ignored, largely it is believed because of the preconception that such feeds are poor quality rather than simply being deficient in some nutrients.

The trials summarized here indicate that cattle growth rates and milk production from mature forage with appropriate supplementation, can often approach the same levels as those obtained on high quality temperate pastures. It is also reported quite regularly that the growth rates of young cattle can be in the order of 0.75 kg/day when they are fed on treated or untreated straw with appropriate supplementation. It should be emphasised that this growth rate of cattle is translated to 280 kg of live weight gain per year and that small ruminants respond equally relative to their size.

The feeding trials reviewed indicate that cattle on a diverse range of mature low protein forage, respond very similarly to supplementation, despite a wide divergence of local climates and different management. The source of supplements is often a key factor and is not necessarily dependent on packaged or bought in items. Thus, for example, tree foliage/sown grasses or other plants that can be grown, may be sources of minerals and escape protein and/or where they have a high digestibility, a source of biomass to increase the digestibility of the diet. The point to be made is that the requirements for essential nutrients that may be deficient in straw or other low digestibility feed may be sourced wherever possible and the above discussion is intended to provide the rules of thumb that have to be applied in developing such feeding systems.

Meat production will continue to be diversified amongst the three major species in extensive and intensive systems and in all countries. However, for the ruminant industry to develop, it will be necessary to identify and to provide the resources that are needed to improve productivity.

The need is for education of farmers to:

• improve their management of straw harvesting;

• manage or treat roughage appropriately to increase its digestibility;

• blend or harvest forage to provide essential nutrients and improve the digestibility of a forage based diet.

The second need is for the relevant industry groups in both public and private sectors to find and make available the essential supplements to ruminants fed on poor quality straw or other forage and to:

• ensure that there is no deficiency of essential nutrients for microbial growth in the rumen;

• provide a source of escape protein to be fed at an optimal rate;

• provide options for drenching with a vegetable oil at the beginning of a fattening period.

Research is needed on all the above points but in particular, to achieve better harvesting methods that would retain the feed quality of straw after harvest. This could mean that treatment with ammonia would be unnecessary and that high growth rates could be achieved with the minimum of supplements.

The last but perhaps most important point, is the requirement for an infrastructure that supports the marketing of ruminant meats and ensures that farmers receive fair and equitable prices.

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