This book is the result of a continuous collaboration between the authors which began at a seminar held by a joint division of FAO/IAEA in Vienna in 1971. The way that we joined forces relates closely with one of our theses - that animal production in developing countries can benefit to a major degree from basic problem-orientated research carried out in a laboratory in a developed country. The reverse is also true - for basic research can be guided and benefit from the stimulation provided by new production systems which extend the frontiers of knowledge especially when these systems utilise new or "unconventional" feed resources.
Several reviewers of the "test" edition of this book considered that some of the recommendations should be treated as working hypotheses and not as "definitive" alternatives to existing ruminant nutrition norms predicated on conventional methods for evaluating feeds and nutrient requirements. However, we find the compromise unacceptable having so often witnessed development failures where the traditional feeding standards and feed evaluation procedures have taken precedence over feeding trials and the use of basic principles based on nutritional guidelines.
We have been accused of "preaching" to our readers as to the virtues of our approach and its relevance to conditions in Third World countries. We never intended this but we do hope to gain converts as our convictions are strong and this therefore comes through in the text.
One of the major reasons we felt the book had to be written is the consistent and repetitive statements relating to the poor nutrient status of animals in developing countries. The constant pressure to feed these animals "more energy" and therefore more cereal grain has been counter productive, leading to dependency instead of self-reliance. It is now recognised that "unthrifty" animals usually are deficient in essential nutrients. When these nutrients are provided by supplementation or manipulation of the diet or the rumen ecosystem, wasteful heat production is 'turned down', and such savings make it possible to achieve moderate levels of productivity.
The basic concepts that have been presented are that the feeds given to ruminants must be chosen and/ or manipulated in such a way that the animal is presented finally with the appropriate array of nutrients needed for a particular productive state. The degree of manipulation (eg. chemical and physical processing and/or use of feed additives) and supplementation with the limiting nutrients will be determined by economic considerations.
Implicit in this general strategy is the emphasis given to basic research in order to examine more closely nutrient absorption and utilisation in relation to various productive functions.
Our suggested guidelines for the development of feeding systems are intended to be pragmatic in so much as they represent compromises between biological, sociological and economic considerations. We have tried to show that the biological principles (eg. the role of glucose as a determinant of efficient feed utilisation on forage-based diets) are consistent with known biochemical pathways whereby nutrients are incorporated into tissues or milk, or used for body functions requiring substrate oxidation.
Continuing research will be imperative for future improvement in livestock production in developing countries and this research should be based on well defined needs. The first priority is to put effort into adaptive research and development (Walker 1987), which for third world countries means taking presently known technology and making it work at the level of the smallholder farmer, who is the primary target.
Basic research, in the context of agricultural development, must be problem-orientated in one sense and visionary in another, in order to further the understanding of why events take place, which is the basis of the biological principles on which new technologies are developed.
Our proposals for future research priorities are divided into three main categories:
Basic research to extend the working hypotheses which have been developed
Applied research, to evaluate new feed resources through feeding trials, and to establish response relationshi ps
"On-farm in-village" adaptive research which aims to take into account the socia-economic constraints and the paramount role of the family unit.
Within this framework, there is a need to develop technology packages that will be readily accepted and applied by the smallholder farmer.
It is not possible to predict the direction in which basic research will develop nor the kind of knowledge that will arise through these efforts. Obviously there is a strong case for supporting research which continues to expand knowledge of the form and function of digestion and the digestive tract and the reactions that take place during digestion and absorption of feed.
Understanding the ecology of the rumen will help to define more precisely the interrelationships between the major species of rumen organisms. This will lead to better "management" of the rumen ecosystem (ie. maintenance of appropriate balances of microbes) in order to optimise the utilisation of available feed resources. Investigation of rumen bacteriophages (viruses and mycoplasmas) may also indicate ways of reducing lysis and turnover of rumen organisms which is a major source of inefficiency (Leng and Nolan 1984). The application of recombinant DN A methodology in order to modify rumen organisms has particular application in increasing the extraction of nutrients from fibrous feeds as digestibility often places an upper limit on production.
Studies of ruminant digestive physiology will have three major objectives:
To define how to extract the maximum amount of nutrients from feed which cannot be digested post-ruminally, with concomitant storage of as much as possible of the energy of feed in end products
To optimise the balance of nutrients in the end products of fermentation, so that the balance is more closely aligned with requirements
To optimise the escape from the rumen, and digestion in the intestines, of protein, starch and long-chain fatty acids in order to complement the products of fermentative digestion.
In such research, the diets to be used should be designed to permit definition of the major objectives which first must be established as a "principle" before attempting to apply the findings. This will facilitate the identification of the "direction" in which the research should go. It will also indicate the interactions which may nullify a particular innovation and it will stimulate researc h to understand the interactions and then to overcome any limitations. For example, if a particular manipulation of the rumen ecosystem is expected to lead to an increase in microbial growth efficiency, then this research will be facilitated by using diets that are low in bypass protein, but adequate in fermentable nitrogen.
The rumen ecosystem has many interacting facets which tend to "dampen" the effects of manipulation. However, it is by examining the apparently conflicting data, and explaining them, that leads to progress. Too often, the negative approach is taken of assuming that research results, which do not fit the generally held view, must be wrong or incomplete. If this approach is not taken many potentially applied breakthroughs may be abandoned at an early stage.
Within the defined objectives there is a need to study and understand the major roles of the individual rumen organisms and their interactions. The selective retention of protozoa and their negative effect on the amino acid economy of the animal is a major area for concentration of research activity because this is a topic on which there is currently considerable conflicting information in the literature. Protozoa have been reported to influence the three areas of digestive physiology considered to have priority. It follows, therefore, that research on the role and control of protozoa should have high priority. For this reason, in the main text we have referred to the results of considerable unpublished research on defaunation from our laboratory.
Individual researchers may identify different priorities within the three objectives cited above. However, the emphasis must be on understanding the nutritional circumstances under which a particular manipulation is likely to lead to improved animal productivity.
The pioneering research on quantitative substrate turnover in ruminants by groups led by Professor Max Kleiber in California and Professor Frank Annison in Australia were guided (motivated?) by the need to understand, in quantitative terms, the availability and balance (array) of nutrients for production. Isotope dilution procedures facilitated this approach and resulted in better insights into quantitative metabolism as this relates to pregnancy, lactation, growth and maintenance. Recently, these techniques have been applied to the quantitation of processes and substrates utilised in muscle metabolism.
Considerable progress was made and was accelerated when these isotope techniques were combined wi th measurements of blood flow, energy balance' (calorimetry) and feeding trials.
Whilst basic knowledge has been greatly advanced there is still insufficient information to relate quantitative fluxes of nutrients in blood with absorption rates and with requirements.
Methods for predicting the nutritive value of a feed, for production purposes, have to be simple. However, often the attempts to simplify have become empirical, dependent on chemic.al characterisation of a feed (ie. fibre content, nitrogen content or digestibility) which are then used to predict levels of production. This has never been satisfactory and we are sure that animal responses to feeds will be more reliable in the long term than feed analysis.
Analyses are needed but should be directed more to monitor the effects of a feed in the animal. For instance, it is more relevant to determine the nitrogen status of the rumen from a measure of ammonia concen trations in the rumen, than from the ni trogen content of a diet.
The efficiency of utilisation of nutrients is the most important factor in maximising animal production from available feeds. The net energy of the feed measures this directly, but in practice is predicted from metabolisable energy, which in turn is calculated, usually from an estimate of the in vitro digestibility of the feed. We' find this a misleading and difficult concept, because the efficiency of utilisation of metabolisable energy is variable and un predictable, as it depends on the balance of nutrients available for metabolism. Moreover, the metabolisable energy content of a feed gives no indication as to whether the rumen fermentation will be efficient, which in turn will effect the balance of nutrients available.
There is an obvious need to be able to predict the efficiency with which a feed will be utili sed for productive purposes. Knowledge of nutrient uptake, and the partitioning of nutrients into various pathways should assist in this endeavour. The acetate clearance test, as discussed in this text, may be a useful guide as an indicator of the glucogenic status of the animal. Amino acid status of the animal can best be estimated by measuring an output highly dependent on the quantity and quality of the amino acid mixture absorbed, (ie. milk or wool production).
For the foreseeable future, crop residues and native pastures will provide the major feed biomass for ruminants in developing countries. Whilst deficiencies of nutrients represent the first constraint to the use of these feeds, their low digestibility is the constraint which eventually sets the upper limit to production. Some byproducts are too low in potential digestibility to warrant their use as a basal diet. Bagasse, palm pressed fibre and coco husks are in this category. For all resources of low digestibility, a major research objective' will be to increase digestibility through treatment of the feed or by improving the capacity of the rumen microorganisms to degrade fibre.
It is necessary to continue to develop methods for treatment of residues to improve digestibility. However it is unnece'ssary to repeat the research that has already established the use of ammonia, urea, caustic soda, mineral acids and steam. These methods are known and are being applied where economic conditions are favorable.
Sugarcane tops present a special challenge because in most countries they are burned to facilitate harvesting. The large amount of biomass presently being wasted has enormous potential for increasing animal production if ways could be found to improve digestibility and to harvest/store the tops economIcally.
Another priority area is the utilisation of the highmoisture pulps, that are also rich in sugar and which, if untreated, undergo rapid fermentation to organic acids and/or alcohol (eg. the pulps from the processing of sisal, coffee, pineapple and citrus). It is important that some means must be found to stabilise and store these feeds.
Sugarcane (or cane selected for biomass production) is believed to have a major role in future ruminant production systems. The high yields are compatible with the objectives of optimising resource use for both food, feed and fuel in the tropics and subtropics. The use of sugarcane, because it is perennial, is conducive to land conservation practices.
The research priorities are in the area of rumen manipulation in view of the very high population densities of protozoa. The balance of sugar to fibre appears to be an important variable which influences the animal response to supplements and the optimum ratio needs to be defined. The alternative approach is to increase the digestibility of the fibrous components of sugarcane. The high moisture content of whole cane, and of the residual bagasse following juice extraction (for monogastric feeding) creates special difficulties in the application of treatment technologies to improve digesti bili ty.
The future lies in utilising least-cost feeds which can be made available on the farm. Research should be directed to the identification and modification of supplements which provide the required nutrients. As there will always be an interaction between the basal feed resource and the supplement, the latter need to be evaluated in the production system where they will be used. The research priorities are:
Evaluation of supplements as a source of bypass protein, bypass starch and non-reactive fat (in the rumen)
Modification of supplements to provide increased availability of bypass nutrients. Heat or aldehyde treatments are the methods presently favoured for protection of protein meals. Other approaches are the blending of natural protein and tannin sources. It would be useful to develop a method of reducing the fibre-depressing activity of long-chain fatty acids, ego by insolubilising them as calcium soaps
Studies on the interaction of supplement and diet. For example, a meal high in oil may reduce digestibility of a forage but not of molasses or sugarcane and at the same time improve the balances of propionate relative to acetate. An apparently soluble source of protein will react quite differently in the rumen of animals fed fibre as opposed to sugar-rich diets
Examination of new and unusual sources of supplements; the foliages of leguminous and nonleguminous trees and shru bs have great potential as on-farm sources of both fermentable and bypass nutrients. One reason for emphasising this is that afforestation is a highly desirable feature of development strategies in the Third World, partic.ularly for soil conservation purposes and the production of fuel. The foliage from most trees contain secondary plant compounds which are often toxic to rumen microorganisms, or the animal. For these reasons, research should aim to develop simple methods for detoxification. The use of recombinant DNA techniques promises to provide solutions by the development of engineered organisms to detoxify these plants.
The final evaluation of promising supplements must be in feeding trials aimed at establishing response relationships for economic evaluation.
In many of the long established agrarian societies, cattle and sheep production depend on grazing of wastelands, crop stubble, communal lands and road sides during the wet seasons and straw and legume (largely lucerne) mixtures in the dry or cold season. The legume component of such diets seldom exceeds 10 - 20% and its protein component therefore provides little bypass protein and is mainly a fermentable nitrogen source. In addition, it provides fermentable carbohydrate, some fat and is often rich in minerals (see Chapter 4). Because of the lack of bypass proteins, mixtures of straw and lucerne art' only marginally better than straw, minerals and urea in supporting animal productivity. These mixtures are imbalanced for critical nutrients which is the primary limitation to production. If the imbalances were to be corrected by supplementation and/or protection of the proteins of the legumes, then digestibility of the basal straw diet becomes the next limiting constraint to improving productivity. Legumes in general have considerably more protein in their leaves than in the stem (see Table 12.1) and therefore in practice it would be more economical to process tht' leaves to protect the protein. This in turn requires development of simple fractionation procedures.
Fractionation of the legume into leaves and stem (high and low protein components) can be simply accomplished physically once the plants are dried. Leaves of legumes with 2-4% tannin may be sufficiently protected to be a major source of bypass protein without further treatment (eg. Lotus pendunculatus and Sainfoin). Lucerne and clover leaves however, contain mostly soluble proteins and simple processing techniques are needed to protect these proteins. Legume leaves are also often high in fat, which is inefficiently utilised by ruminants fed straw-based diets unless bypass protein is also provided in the diet (see Van Houtert and Leng 1986).
Where environmental temperatures are high, simply placing a thin layer of leaves on black plastic or between clear and black plastic may be all that is needed to raise the temperature to between 80 and 100°C which is sufficient to give a moderate to good level of protection in the protein (see Table 7.14 ). On the other hand, in climates with extremely cold winters, freezing over night of the dried leaves, with or wi thou t added water, may also result in some denaturation and therefore protection of the protein (see Table 7.13). If the leaves are treated to protect the protein from rumen degradation, the stems (which are lower in protein and more highly lignified-see Table 12.1) can be use to provide some of the requirements of the animal for fermentable nitrogen in the rumen but in most situations additional urea may also be needed.
|
Table 12.1: Crude protein (CP) and fat levels (ether extract) (%dry matte1) in leaves and stems of some legumes gr011:n as forage crops for feeding with straw-based diets to sheep and cattle in Gansu Province - China. |
||||
|
|
Crude protein. % |
Fat |
||
|
|
Leaf |
Stem |
Leaf |
Stem |
|
Lucerne Medicago sativa |
36 |
15 |
5 |
1.5 |
|
Sweet Clover Melilotus officinalis |
36 |
14 |
5.5 |
1.2 |
|
Lotus cornuculatus |
26 |
10 |
4 |
2.0 |
|
Astragalus adsurgens |
22 |
9 |
3 |
1.0 |
|
Sainfoin Onobryohis sativa |
29 |
16 |
4.1 |
2.1 |
|
Crown vetch Vicia sativa |
25 |
11 |
4.1 |
2.1 |
|
Hairy vetch Vicia villosed |
35 |
21 |
4.7 |
1.8 |
|
Source: Lingmei 1987 |
||||
If these techniques could be applied at the small farmer level, together with the use of ammoniated or fractionated straw (see below), ruminant productivity increases could be spectacular: the higher digestibility ensuring high intakes and the extra amino acids from the legume ensuring high efficiencies of utilisation of the available nutrients.
In many parts of the world, fuel is now in very short supply and is a primary limitation to the well being of subsistence farmers (McNamara 1985). For instance, on the Loess Plateau of Northern China, straw is used approximately equally for feed for ruminant livestock and for fuel for heating and cooking particularly during the cold, winter months. The importance of straw as a fuel in these areas should encourage fractionation of the whole plant into food (ie. the grain), feed (the most digestible components) and fuel (the least digestible components). This can be done when the plant is threshed. As an example, a convenient method of fractionating the straw plant into the desired components is to use a guillotine to cut the bundles of cereal plants in half. The roots and lower stems (the plant is harvested by hand and is often pulled from the soil rather than cut), which are the lowest digestibility fractions can be separated and stacked as a future fuel source. The higher digestibility leaves-upper stems and seed heads-can then be thrashed. In some parts of China this is already practiced in order to reduce the work load on the oxen (Yu Feng, pers. comm.). The digestibility of the leaves and aerial parts of the cereal plant may be up to ten units higher than the lower parts. This is a comparable digestibility to that conferred by ammoniation or urea ensiling. This simple procedure could, for instance, result in increased growth rates of cattle fed straw-based diets of the order of 200-300 g per day as demonstrated by Perdok and Leng (1987) with untreated and treated rice straw (see Chapter 8).
A further method of fractionating the higher digestibility feeds which is of significance particularly for sheep and goats, uses the selective ability of the animal to fractionate straw. Sheep (or goats) given a high degree of selection of the dry matter of straw (or mechanically fractionated straw) will select the highest digestibility fraction allowing higher intakes and production levels (see Chapter 8).
The fractionation procedures suggested should be simple and practical. They will, however, be difficult to communicate to the large number of small-scale farmers and are therefore difficult to implement unless some easy methods of conveying the techniques are available. The way forward appears to be to provide the farmer with some form of inexpensive gadgetry which encourages the application of these technologies. For example, simple machines to cut cereal plant bundles in half and simple effective feeding racks which allow selective feeding and at the same time allows the rejected straw to be kept clean and easily collected.
The other important point is that simple methods for drying legumes, fractionating them into stems and leaves and heating them with solar energy in order to protect the protein will be of considerable benefit to large and small farmers alike provided the technology is appropriate.
Disillusionment with the Metabolisable Energy system for establishing feeding practices began when attempting to develop feeding systems based on molasses or sugarcane (Preston and Willis 1974; Leng and Preston 1976). It became apparent early that high levels of milk production could not be obtained from these sugar based diets, even though the diets were supplemented such that the supply of "metabolisable energy", fermentable nitrogen and bypass protein should have been adequate. When maize grain replaced molasses, there was an increase in propionate in the VFA in the rumen and milk production increased linearly with the replacement of molasses by maize (see Chapter 8). Similarly, on sugarcane diets, metabolisable energy was not useful in predicting growth or productivity and the supplements that provided glucose for absorption were the ones that apparently improved the efficiency of feed utilisation greatly (Chapter 8).
The hypothesis which developed from these findings - ie. that glucose could be a limiting nutrient for production, particularly for milk solids, was the stimulus for much of our subsequent research, both basic (ie. on the requirements for glucose and interactions with other nutrients) and applied (feeding trials with bypass protein).
In Chapter 4 we give many illustrations of research data which lend support to this hypothesis and in Chapter 8 we have shown how these concepts have assisted in the development of feeding systems. However, it is relevant to cite yet another example of the inefficient and unpredictable use of metabolisable energy in order to emphasise the inadequacies of the metabolisable energy system generally.
In a feeding trial with sheep (see Table 12.2), Geenty et al. (1987) compared three diets: a highly digestible clover/ryegrass, a grain/bypass protein (fish meal) and a grain/low protein diet. The grass/clover diet was used inefficiently when compared with either of the two grain-based diets. Intake of metabolisable energy on the grain/low protein diet was much lower than that on the clover /ryegrass" but growth rates were similar and therefore feed conversion was much better on the former.
|
Table 12.2: Efficiency of feed utilisation by lambs on grain/hay diets as compared with green clover/rye grass cut and fed ad lib. (diets were about 80% digestible). |
||||
|
Diet |
LW gain |
ME intake |
Protein intake(g/d) |
FCR |
|
High grain-protein pellet |
253 |
13.5 |
226 |
4.5 |
|
High grain pellet |
130 |
9.7 |
118 |
6.4 |
|
Cl;over/ryegrass |
143 |
13.0 |
292 |
7.7 |
|
After Geenty et al. 1987 |
||||
The guidelines we advocate for developing feeding systems, are based on the principles of:
1. Maximising rumen function by
Providing (balancing) nutrients needed by the rumen microflora
Improving the physical attributes of the rumen ecosytem by supplying:
small amounts of readily digestible fibre to improve the rate of microbial colonisation of the basal forage
long fibres to stimulate rumen motility
2. Optimising the balance of nutrients for metabolism by:
Supplementation of the diet with bypass nutrients and unreactive (rumen) source of LCFAs (ie. fat prills or calcium soaps)
Increasing the bypass (escape) of protein and starch or the propionate concentrations in the rumen by:
manipulating propionate production in the rumen (with chemicals or natural products ego cottonseed)
protecting the supplement to increase the amounts entering the intestines (eg. reacting protein with formaldehyde) selecting supplements containing agents to protect proteins (eg. tannins to react with soluble proteins) control/elimination of rumen protozoa
Reducing endogenous nutrient losses (eg. by control of internal or external parasites)
3. Increasing the potential intake of nutrients by raising the rate and extent of digestibility of the basal feed through chemical/physical processing
4. Optimising the quantities and balance of minerals by using, wherever possible, inexpensive organic supplements or byproducts providing critical organic nutrients which are, in addition, rich sources of minerals.
There is no reason to believe that future knowledge will lead to changes in this general approach. Under existing circumstances in most developing countries it will be sufficient to make decisions on a simplified basis utilising the biological instincts of the animal to "balance" its diet through "choice" feeding; coupled with control exercised by the farmer according to economic criteria (on the basis of output/input relationships) .
With respect to the rumen ecosystem, it is probable that in most situations, biological maxima will coincide with economic optima as the required nutrients/interventions are usually of low cost and/or the amounts needed are small (eg. sources of fermentable nitrogen, other micronutrients) or will be supplied in a supplement chosen to provide bypass nutrients (eg. foliage from leguminous trees).
Free choice feeding of a multi-nutrient block or liquid supplement enables the animal to decide on the amounts to be consumed and is an appropriate way of optimising rumen function.
Balancing nutrients for the animal can rarely be done by choice feeding as bypass nutrients are relatively expensive because of a high opportunity value (eg. protein meals) or are labour intensive when produced on the farm (eg. foliage from legume trees). The amounts to be fed, therefore, must usually be controlled according to economic criteria.
The precision of the decision-making process as set out in the recommended "guidelines" must be improved. This can only be done by developing multifunction response relationships utilising computers. Fortunately, this option is becoming more feasible as microcomputers become more readily available and of lower cost.
There have been many attempts to use computeraided modelling techniques to relate nutrient availability to nutritive value of a feed, of which the most recent example is the work of Black et al. (1987ab). This approach is extremely important and must be encouraged, despite the difficulties caused by interactions and associated effects, as it identifies the relevant areas for research and the constraints at the tissue level.
The danger of modelling is when the end purpose is to develop feeding systems with a "black box" approach. We reiterate our thesis which is that "understanding" is paramount in the development 'of an animal production systems and that models are an aid to that end and not an end in themselves.
For models to become more useful it is necessary to improve the "quality" of the inputs. In this respect, we believe it will be more meaningful and progress will be more rapid if efforts are concentrated on measurements which can be made in the animal rather than on the feed.
Estimations of degradability in the rumen with the in sacco technique are more valuable than in vitro digestibility measurements because it is possible at the same time to evaluate the efficiency of the rumen ecosystem and its response to supplements. This latter issue can be addressed in vitro by a simulated rumen technique such as RUSITEC (Czerkawski 1986). However, the technique is neither simple nor appropriate for most laboratories in developing countries, where it is easier to establish and maintain fistulated animals. At best an artificial rumen technique is still only a simulation of the real events in the animal.
Rate of degradability in the rumen (in sacco technique) of protein and starch appears to be reasonably well related to the bypass (escape) of these nutrien ts from the rumen fermentation. The rate of acetate clearance from blood appears to be directly related with the glucogenic status of the diet.
.
Based on the principles of digestion and metabolism outlined in Chapters 3 and 4 there are good reasons for suggesting that the following measurements in the animal will be positively related with economic criteria (ie. animal performance):
Rumen fluid ammonia concentration
The relative population densities of protozoa, fungi and bacteria
Rate of disappearance (from nylon bags) in the rumen of organic matter, protein and starch from the feed
Rate of disappearance (in sacco) in the rumen of cotton wool or a standard fibre source (measures efficacy of the rumen ecosytem to degrade fibre)
The proportion of propionic acid in the total VFA in the rumen
Rate of acetate clearance from blood
It is recommended that these measurements are made routinely on animals in feeding trials designed to measure response to supplementation/manipulation of an "unbalanced" basal diet. These measurements would then be related to observed animal performance using multi-facet models, the final aim being to design feeding systems based on the results from these short term biochemical measurements made in few animals.
The Metabolisable Energy system should be abandoned as the basis for designing feeding practices in the tropics and sub-tropics where the typical feed resources are deficient in protein and glucogenic precursors. Even in temperate countries, its application must be questioned because of the conceptual problems inherent in the assumptions that have to be made in its application to intensively-fed ruminants. The impossibility of applying the system in situations where intake of the basal diet cannot easily be measured has led to research scientists and producers alike often ignoring poor efficiencies of feed utilisation. For instance, the balance of nutrients from a grazed pasture has not been taken into account in programmes aimed at breeding grasses with improved nutritive value for ruminants. To our knowledge, no pasture breeding programme considers the fermentation patterns in the rumen as an important criterion.
Recently, the potential for proteins to be protected by tannins in pasture plants has been highlighted by Barry (1985) and the possibilities of breeding or genetically modifying plants to contain an appropriate level of tannins that will just protect plant protein from rumen degradation has been suggested (T. Barry, personal communication).
In the words of Graham (1983):
"the Metabolisable Energy system is an outmoded concept in ruminant nutrition".
In our opinion, the effort (and funds) presently being expended on further developing feeding standards based on metabolisable energy would contribute much more to general knowledge if it were directed to studies of the concept of balanced nutrients. The balance of nutrients approach, based on measurements made in the animal, is conceptually correct and can be used at different levels of sophistication.
In the most simple form, the basal diet is balanced by:
Allowing the animal free access to a multinutrient supplement providing urea and minerals
Giving bypass nutrients: 5% of a diet as cereal milling byproduets (eg. rice polishings) or 25% of the diet as a foliage from a legume tree (eg. gliricidia or leucaena) will generally meet the requirements.
In a more sophisticated approach, the amounts of supplements to be fed will be decided by a computer model the inputs to which will be some of the biochemical criteria proposed.
It is therefore strongly proposed that future research should address the following issues:
Identifying, improving, and also simplifying, the methods for determining:
the proposed biochemical parameters (rumen ammonia, acetate clearance rate etc.)
the quality of a feed using the animal (rumen degradability of organic matter and protein) or
the efficiency of the rumen ecosystem (rumen degradability of cotton wool; protozoal densities).
Developing new methods based on the principles of rumen fermentative digestion and metabolism.
Develop models of the rumen and the rumen / animal to more closely describe the mechanisms that control production levels
Develop econometric models which will make use of the above information to compute least-cost combinations of the basal feeds and the supplements/manipulations.
In many parts of the developing world, diseases restrict animal production. Our discussion of the interaction of nutrition with disease has been restricted to considerations of parasitism. This is because we could find very little literature on other aspects of disease-nutrition interactions.
There appears to be some evidence linking nutrition and resistance to the Tsetse fly-transmitted trypanasomiasis. It has been suggested that "well fed" (with concentrate?) cattle suffered only minor stress when challenged with trypanasomiasis whereas mortalities are high under field conditions. If this is correct, the application of the principles of strategic supplementation may be very rewarding in areas where this disease is endemic.
Intestinal parasites, particularly under conditions of communal grazing, are often a major limitation to production. Their effects may be ameliorated by application of nutritional principles. The control of intestinal parasi tes in grazing ruminants is no longer a "hit or miss" procedure. In Australia, it has been shown that strategic use of specific and broad spectrum drenches, based on sound epidemiological principles, can at least minimise and at best eliminate parasitic infestation of sheep (Dash 1984).
Experience suggests that it is difficult to implement scientific innovation at the level of smallholder farmers. The reasons for this are many and varied but a major problem is the difficult task of disseminating information which is compounded by the large number of farmers that are the targeted group. Secondly, the innovation must be adapted to their particular conditions.
The concept of the multi-nutrient block obviates some of these difficulties. Such an approach has great potential for the introduction of scientific innovation.
The potential of multi-nutrient blocks in the management of village animals includes:
Administration of nutrients
fermentable N
trace minerals (eg. Co, Zn, Se, Cu)
macrominerals (eg. S, Ca, P)
vitamins (eg. A, D, B)
small quantities of protein to provide rumen micro-organisms with amino acids, peptides, branched-chain fatty acids and other essen tial nutrients
Administration of chemicals to manipulate rumen fermentation
anti-protozoal agents
methane inhibitors (eg. monensin and fat)
enzyme inhibitors to reduce breakdown of soluble proteins and amino acids
Administration of drugs either over a short or a prolonged period for control of:
flukes ticks
endoparasites
vaccines (?)
Administration of hormones for manipulation of growth, lactation and reproduction (?)
Administration of chemicals to control fly development in faeces. This could be important for human health.
In many cases, new methods will need to be developed to ensure that the chemical, drug or hormone is protected from rumen fermentation or from digestive enzymes and that it is absorbed effectively (eg. in the case of large molecules). Some of these ideas may seem futuristic, but the target is so huge (eg. 65 million milking buffaloes in India alone), as to justify the research/effort that would be needed.
Incorporating chemicals or drugs into the block to manipulate fermentative digestion and/or to control parasites and diseases would make it easy for farmers to take advantage of many of what appeared on first sight to be more esoteric research findings.
India, through its National Dairy Development Board, has taken the lead in introducing the molasses block technology but other countries are beginning to examine the possibilities for applying it within the established management practices. For example, FAO is assisting several coun tries in Africa to manufacture and distribute urea/molasses blocks (Sansoucy 1985).
Where it has been introduced, the block technology appears to be readily accepted with few socioeconomic constraints. One of the advantages of the technology is that it facilitates the application of scientific principles of optimising the use of the available resources (straw, indigenous animals and the smallholder farmer).
Self sufficiency in food for the family and feed for the livestock is the first priority of the smallholder farmer. Only after these needs are met will surpluses be sold.
Marketing of produce is rarely considered to be a first priority in development programmes. In India the dairy co-operatives, which have been so successful, had at their inception the priority of creation of an infrastructure for the collection, processing, distribution and sale of milk and milk products. This ensured a build-up in demand for milk and stimulated the smallholder farmer to increase productivity over and above the immediate needs of the family.
Initially, the increased productivity came from the feeding of "balanced concentrates" but through a vigorous quest for information and training this technology has been modified to emphasise the use of strategic supplements (molasses/urea multi-nutrient blocks and bypass protein) to provide nutrients deficient in the basal diet.
The point to be made is that the availability of the market was the initial incentive to increase productivity. This in turn permitted the introduction of improved nutritional practices.
Although outside the scope of this book, soil conservation cannot go unmentioned when discussing perspectives. The ultimate resource is the land on which the biomass is grown and on which animals depend. Without minimisation or elimination of soil erosion, then ultimate failure of the farming system must occur. Similarly, failure to maintain or increase soil fertility will also lead to decreasing biomass production, eventual soil erosion and eventual failure of the farming system.
Supplementation and overgrazing
Many of the strategies discussed in this book are entirely feasible in particular environments, whereas in others their application could be Ii mi ted by the consequences on soil erosion (eg. increasing feed intake of ruminants on over grazed grasslands). In this context, the scientist involved in development must be at least appreciative of the effects of introducing innovations such as supplementary feeding.
Supplementary feeding of grazing cattle, should be introduced when biomass production has been improved or conversely stocking rates should be decreased. This is particularly important where prolonged dry seasons are a prominent feature of the climate. However, the restricted grazing of most of the grasslands in the third world countries and the enclosure of animals at night may remove this apparent constraint and increases in productivity by supplementation are attributable to the accompanying increased efficiency of feed utilisation. The net result is to optimise the utilisation of the grass lands and the feeds given in the corrals.
The introduction of legumes into pastures should be advantageous, increasing the total biomass. However, unless these are moderately rich in tannins they do not provide the nutrient status (particularly prot.ein) conducive t.o efficient. utilisation of past.ure. Then> are many legumes, that because of the palatability or presence of t.oxins in their leaves are not. consumed by livestock or they are only consumed well into the dry season when feed is scarce. These could be important components of pastures helping to stabilise land and at the same time provide nitrogen fixation for better growth of companion plants. The combination of edible and inedible legumes in the pasture, strategic supplement.ation with fermentable N (ie. nutrient blocks) and protein meals, feeding crop residues in the stalls at night are all parts of strategy that could lead to large productivity increases from pastures. In this respect, the combination of tree legumes and pastures must also be considered.
We do not presume to discuss areas of specialised land conservat.ion mechanisms but point out here the essential requirement.s for improving livestock production and how it might impinge on the farming systems of the highly erodable soils of areas such as the Loess Plateau of Northern China.
The first priorities for rural dwellers is an improvement of standard of living and creation of wealth. For these reasons, the sought-after vocations are in law and medicine. Training in agriculture has a poor image whereas there is a national need for well-trained technicians at all levels from field officers through to teachers and researchers.
Education and information dissemination are fundamental to development and must therefore be ongoing activities. This is recognised by Aid Agencies and the first priority in development projects is often the dispersal of the "bright young men and women" to various centres of excellence in the discipline(s) that are considered necessary in the light of the overall development objectives. Often this causes the program to "mark time" until the trainees return, at which point "gaps" in the development project may become apparent.
It is frequently believed that it is the "training" (for PhD or Masters) which is the all important aspect; and that - what, where and why - is relatively less significant.
These beliefs are no longer acceptable . It is imperative that young scientists are trained within the particular discipline but with their applied goals (of contributing to development of their own country) firmly in perspective.
So many young scientists return to their own countries with limited technology (training), frequently directed into a narrow research project often irrelevant to the problems they have to tackle in their own country. Quite often they are used as 'inexpensive labour' in a locally financed research programme. On their return to their country, because they have been "trained", they are expected to carry out the necessary literature search and identify the most appropriate and relevant research plan to solve the most economic animal production problems.
Undou btedly there is a role for overseas training and this will be facilitated if the supervisor has development experience and is sympathetic to the research needs of the student. Time that is spent in a laboratory in a developed country, in order to acquire technology and understanding through association with scholars, is usually highly beneficial. Priority should then be given to a reassessment of the problems to be researched by spending periods in the field in their own country to collect data which can then be analysed and written-up in the training centre.
Scientists who do not know the literature are likely to repeat research which has already been completed elsewhere. However, even the most diligent search will not unearth the data that have not been published. Access to what is known, and the lack of opportunity to publish are familiar problems in most developing countries. Library access is usually limited and publication of scientific papers for international readership is, in general, rigorously controlled.
Research work is generally unpublished for three major reasons:
The manuscript cannot get past editorial boards
The working hypothesis was proven (ie. the results were negative)
The research scientist has neither the inclination or time for the arduous task of writing a scientific paper.
In this book we have drawn considerably on unpublished (soon to be) data from our studies or provided by colleagues. The presentation of such data was criticised by some referees in the preliminary edition and is likely to be criticised further. The justification is our confidence in the relevance of the data, which obliges us to make the information accessible to a wider audience.
A major problem is that communication between developing countries with the same environmental constraints is difficult. Often, there is no common route for publication which tends to be through the "prestigious" Western journals, w here scientific merit overrides applied significance.
We recognise the need for rigorous research methodology but we are equally aware that in practice important developments often begin with demonstration trials or simple observations, provided that both are based on sound scientific principles. There is a great need for a journal sympathetic to these ideas but which is not a "soft option for publication".
These statements concerning publication of research are likely to arouse much discussion. An outstanding example of the need for rapid publication and sympathetic. refereeing came from experience in publishing data on bovine hyperexcitability. When this was first observed in cattle fed ammoniated straw in our laboratory we became alarmed because at that time wide scale application of this technique was being advocated in Europe, USA and many developing countries. Once we had established that we could repeatedly obtain this condition, we felt a need to meet the responsibility of reporting the observation, since the effects on ruminants were horrifying and there was potential danger of toxic elements entering the human food chain. We chose to submit a paper to the journal Nature because of its wide readership both in industrialised and developing countries. However, the responsibility we felt was not shared by a referee of the paper who rejected it outright with the most quotable of quotes:
" the authors were scaremongers of the worst possible type"
We attempted to answer the criticism and included data in the next submission to Nature on the fact that toxic components were transmitted via milk and therefore there was some danger to human health . However, the paper was again rejected.
Still feeling a strong responsibility, but unable to have it published quickly, we eventually submitted a full paper (Perdok and Leng, 1987) to Animal Feed Science and Technology which is a journal which has published considerable research on treated straw as feed for ruminants. The reader may be able to imagine our delight at the response of the new referee:
" .. .I see no alternative than to accept the paper and rush it into print"
This was quite the opposite to the response of the previous referee.
The importance of our early observations has been strongly supported by a recent report showing widespread incidences of bovine hyperexcitability in Spain. This work dearly shows that ammoniation of straw in stacks when done in summer and after 1100 hr in the morning, when temperatures are high, is quite likely to result in production of toxic compounds which induce disorders leading to death when the straw is consumed by cattle or sheep (Cabrera et al. 1987). Our paper, carrying an early warning, was delayed two and a half years. The use of ammoniated straw in dairy cow diets during that time means that humans must have consumed, at times, some milk containing the toxic principal.
The second reason for not publishing, (ie. the negative result) is more difficult to reconcile. Negative results are often valuable and their non-publication may mean that in a "marginal benefits" area attention is only given to the positive findings.
It is very difficult to reconcile the attitudes of researchers who do not publish. The huge cost of research, the possibility that research will be repeated (whether it is published or not) tends to compound the costs. Despite the obvious need to carry out research that is well controlled and then reported, researc h scientists often excuse their tardiness on the basis of workload. In our opinion this is inexcusable.
Young scientists must be encouraged to publish their research for the reasons which have been stated.
The final statement on communication is focussed on human interactions because these are the ultimate means by which information is finally assimilated into practice by farmers. New ideas, new information and technology (breakthroughs?) suffer initially from natural human negative reactions. Possibly biological scientists are the most cautious of all technicians in accepting a potential breakthrough. In general the reactions of scientists to new concepts in order of the passage of time are:
It is not true
It is true, but it is not important
It is true, it is important but it is noit new
Prevarication among scientists is a major reason for the slow application of new innovations. The direct testing in a farming system of the innovation soon shows up any weaknesses in the application. We hope the readers of the book will take the information, 'new' and 'old' concepts and in particular the approach to developing feeding systems and put these to the test under farming conditions and then return to their laboratories to study the local problems that will inevitably arise.
Our book has three major objectives:
To present a scientific basis for improvement of livestock production within the framework of utilisation of local resources
To demonstrate the likely responses to applying this information in production systems and from this to establish guidelines for future development
To presen t approaches to the application of technologies within the socio-economic constraints of a rural development strategy.
To achieve these objectives we have drawn on information wherever it could be obtained. We are convinced that the underlying concepts are sound. But we anticipate that some of the detail will be wrong. We will correct any errors in future editions which we intend to update at regular intervals.
Above all we hope that we will succeed in stimulating a fresh approach to an old subject.
 |
|
Tree forages are becoming increasingly important as protein supplements to ruminants fed agro-industrial byproduets and crop residues. Tree crops planted to be used as forage for supplementing cattle in Colombia (Preston T R) |
 |
| In cropping areas ruminants are often confined to crop residues, crop stubbles and grazing erosion gullies. Erosion combined with overgrazing is a major problem in many developing countries (Loess Plateau-Leng R A) |