Changing need in cattle feed
Animals in industrilized countries both farmers and animals are becoming specialized. Thus dairy farmers keep high milk producing cows. Beef farmers keep specialized beef animals - sheep are specialized in producing meat or wool. Likewise the crops are specialized and crop residues generally discarded or ploughed in.
This total market orientation lead to security in homogeneity both of crop and animals.In the new case of this is achieved by intensive selection using AI and embroyo transfer.
In developing or less industrialized countries the environment cannot usually be controlled.As the animals have many functions thus diversity has survival value. Moreover, animals selected on the basis of homogeneity will not fare well as it is simply illustrated by the many failures of importations of "upgraded animals" from industrialized countries to less industrialised countries.
The feed resources in crop livestock systems in less industrialized countries. Only little attention will be given to the animal product which are many and varied. In the case of ruminants they contribute directly to human food in terms of milk not meat products. They contribute wool, hair and skin for clothing, carpets and shelter. Most important they contribute indirectly to human food by providing draught power for cultivation. They contribute to threshing and transport. They supply dung for domesticfuel, manure and building material. As distinct from industrialised systems both animal manure and crop residues are valuable resources.
Perhaps on a global scale the most important products the animals produce is their role in providing security and prestige and their important contribution to risk aversion. Animals are often sold when cash is needed for school fees and other important items. They can often absorb excess labour as more feed can be collected when labour is available. The most important animal products are so to speak maintenance and survival. Many of the products mentioned above can be substituted by fossil fuel such as draught power if this was economical and more feed could be used for production of milk and meat. The animals role in security and risk aversion can only be changed by long term political and economic stability.
Regardless of product there is a finite amount of feed resource available. In the following emphasis will be given to feed used in crop livestock systems rather than in rangeland systems as there is probably more possibilities to enhance utilization and feed availability in such systems.
Crop residues constitute the major component of feed for ruminants in almost all small scale crop livestock systems e.g. straw from rice, wheat, barley, stovers from maize, sorghum and milet and stalk from ground-nut sweet potatoes etc. bagasse and molassis are available in suger can areas. In some areas small amounts of cultivated forage are available. A limited amount of higher quality crop residues are available such as wheat, rice and maize browse and leaves from trees and bushes and city by products such as brewers grains. A small amount of grazing along roadside and edges of fields and ponds in also available and in rainfed areas the fields can be grazed in the dry season.
Genetic selection of straw The simpler and cheapest way to improve crop residues would be if it could be done by genetic selection. Here there are real and almost totally unexplored possibilities. Plant breeders have hardly ever taken quality of crop residues into account in selecction indicies. Thus the International Rice Research Institute in the Phillipines pay no attention to quality of straw.
In the past there were some good reasons for this because straw quality was difficult to measure rapidly. It could only be done by large scale digestibility trials in which groups of animals were put into crates and their excreta collected. such difficulties no longer exists. Biological methods are now available which can rapidly and reliably test quality of crop residues.
In 1986-87 The International Feed Resources Group in Scotland tested up to 100 varieties of grain from wheat, barley and oats. The quality of barley and wheat in particularly showed wide variations. In fact the variability was such that groups of cattle grew 300 g/d more from consuming one variety of straw than another. such work has now been published also from Indonesia using rice straw, from India using variation of rice straw and sorghum stover, and from Syria using barley straw varieties, to name but a few.
A negative correlation between grain yield and straw quality has never been reported so the 2 aspects can be selected for at the same time. It is worth pointing out here that farmers have been known to reject new varieties of grain due to the poor quality straw or stovers they produced! Crop residues are very important for most farmers in crop livestock areas.
Are the causes of genetic variability due to differences in botanical fractions or due to differences in quality of individual fractions? Seperation of botanical fraction
Cereal straw contain essentially 4 separate fractions, the stems, the leaves, the nodes and the chaff (from the flowering parts). the latter two fractions constitute about 15%. Of these fractions the leaf is by far the most the digestible except for rice straw and the stem the least digestible. rice straw is an exception as the stem is more digestible than leaf.
the smallfraction of nodes and chaff are intermediate. It is thus possible to alter the quality by selecting for a greater proportion of leaf in the straw. In most examinations of genetics variation in straw quality differences in leaf to stem ratio have not been nearly so important as differences in quality of the individual components. This is interesting. Oftern there are no differences in the lignin content which is the products that holds it together but there seem to be differences in the architecture of the straw. It could be tempting to ask whether straws of high nutritive value would also be prone to lodging but there is no evidence for that.
The digestibility of straws and stovers (Stovers are the same for straw from maize and sorghum and millet) is normally between 40 and 50%. Differences in digestibility of 10% may not seem much but it can have pronounced influence as to how much the animal can consume. sometimes they can eat 30 to 50% more even if the differences were only 10% units in digestibility and therefore cause large differences in performance of the animals. In spite of the large differences in straw quality reported for all cultivated grain varieties there is still an unwillingness of plant breeders to pay attention to this. If in India and Bangladesh for instance with such large cattle population an increase in digestibility of crop residues by 10% was possibles at little or no cost it could have a revolutionary influence on animal productivity.
It could be argued that if the leaf fraction was so much better than stems, then if there was surplus of straw it would be best if the leaf fraction could be fed and the stems discarded. In effect small ruminants like goats and to a lesser extent sheep do just that.
they are reluctant to eat the stems and can to a large extent select the leafy parts. So if sheep and goats are given say two times as much straw as they consume they can achieve quite a high performance as what they have eaten is high quality feed.
In some industrialized countries there is a desire to do wthat separation for another reason altogether. The reason is that the stem fraction is almost like wood in chemical composition and therefore very suitable for paper and hardboard making while leaf is not, but fortunately leaf is best for the animals. A fractionation thus add value to both fractions. From a future perspective this opens up possibilities for plant breeders not only to select for the highest quality for animal feed but also the highest quality for industrial raw materials. High nutritive value of leaf in again not correlated with industrial quality of stems. A separation method often used by small farmers in Indonesia and China for maize stover is to remove the leaves for feeding to animals and use the stalks as domestic fuel.
Upgrading of straw
The digestibility of straw is about 40 to 50% and the reason for the low digestibility is the lignin which prevent bacteria in the stomach from penetrating it. Thus if the lignin could be loosened or dislodged then digestibility could at least theoretically be about 90% as the indigestible lignin amounts to about 10%.
Upgrading can be done by alkali which swells some of the lignin bonds so more cellulose and hemicellulose is exposed to bacterial action. Caustic soda was used in Germany already during the first world war to make more feed available for animals. Caustic soda is a strong alkali and generally the most effective but it has little or not practical application due to the danger in using it and the environmental consequeces of high sodium levels. However the much weaker alkali ammonia is applied in many places.
In industrialized countries it is either gaseous ammonia or ammonium hydroxide as industrial suppliers provide the chemicals in tanks to large farms. for small farms however another product has become much more popular namely urea. When urea is hydrolysed ti yields ammonia. Urea is a relatively harmless substance it dissolves easily in water and can be applied to small quantities of straw. The level of inclusion is about 5 kg urea/100 kg of straw. The stack needs to be covered with mud, plastic, banana leaves, planks etc., depending on local availability.
Several million Chinese farmers are now using this method but also some Indian, Bangladeshi and Iranian farmers. digestibility is usually increased by about 10% unit. The treatment is complete in 10 to 20 days depending on external temperature (the method cannot be used during very cold periods).
Due to the importance of this method for small scale farmers in developing countries it is perhaps worth just to discuss one more aspect namely the economy of using urea/ammonia treatment. However, there are certain conditions which must be present before one can recommend this intervention to farmers. First of all urea has to be available all the time. Secondly the price of urea has to be such that making straw more digestible is the cheapest option. Let us say that 5 kg urea generated 10 kg of digestible matter from 100 kg straw which imply 1 kg of urea generates 2 kg of digestible matter. If high quality material such as rice bran cottonseed etc. can be bought cheaper and with less labour then urea treatment should be advocated. If there is a surplus straw then the urea treatment enable the animals to consume sometimes 30 to 50% and a much higher performance can be achieved. It was the surplus straw and high demand for beef which has made treatment such an attractive medhod for small farmers in China. Alternate methods of treatment:
Oxidative method
Instead of swelling the bonding to lignin it is possible to oxidize it with use of for instance hydrogen peroxide in alkaline solution. Use of peroxie has the advantage that the oxidation product is water. this method is far too expensive. The same can be said for acid treatment of make straw more digestible.
Biological methods
The use of a white rot fungi which supposedly utilize lignin has been tried in many places including NDRI Karnal Haryana. The problem is that too much substrate is lost. The fungi uses from 20 to 40% of the substrate in order to make the remainder a little more digestible. Such methods need to be combined with production of human food from the fruiting bodies of the fungi such as pleurotis austreatus species.
Use of enzymes
A great deal of progress has been made in isolating enzymes for exogenous degradation of straw. Mixtures of xylanases and cellulases are used. so far exogenous enzymes cannot break down substrate which is protected by lignin. It has the potential to generate soluble sugar from cellulose which in turn can ferment to fermentation acids and make ensiling of straw possible. Perhaps in the future it could be used as a method of preserving wet harvested rice straw which is often wasted.
Setting fields of paddy straw and other crop residues knowing, that it could be used as animal feed with resultant manure which could be used as fertilizer for better than ashes from burned straw.
During some harvest the paddy straw needs to be dried or otherwise preserved. The problem is often one of labour and another crop needs to be planted. Here it should at least be mentioned the urea treatment described above also achieve to preserve the straw as the ammonia generated prevents mould development.
In many areas particularly in Africa stovers from maize sorghum and millet are grazed by animals in the field and the remainder ploughed in for next harvest. when the maize cob is removed the stalks are often still green and considerably higher nutritive value than it is later when the soluble material is the green stalks has disappeared. There is a need here to develop new methods of preserving stovers in such a way that the maximum amount of nutrients are retained.
On small farms in China what is called maize silage is actually silage made from talks after the cob has been removed. there is room for innovative methods of drying green thick stalks which also include cultivated foragee like Napier grass which sometimes provide excessive biomass in the wet season. The quality of such biomass deteriorate when it is more than 1 m high so methods of drying or preserving thick green stemmed material is needed.
Cellulosic feeds and supplements
Supplements are here understood products of higher quality which may or may not be produced on the farm but often produced at small village mills such as rice, maize or wheatbrans cottonseed, mustard seed, noug cakes and many more. In sugar can areas molasses may be available for feeding.
Here we must again consider that crop residues by definition is not whole crop it is therefore like that they are deficient in some nutrients since the main product like grain have accumulated the essential nutrients necessary to accomplish germination.
Supplements are therefore critical in so far that they must contain if possible the limiting nutrients in crop residues. In most instances the limiting nutrient is nitrogenous compounds which can yield ammonia for the bacteria in the rumen. If this is limiting, the speed of digestion will be reduced and due to longer time in the rumen the animal will eat less and digest a smaller proportion. Alleviating that can have dramatic results on straw utilization.
Another aspect of crop residues which often limits it utilization is that even if there is adequate nutrient for the bacteria they may grow so slowly on poor quality feeds that the number of bacteria in solution in their rumen limits the speed at which new feed is being colonized and therefore degraded by bacteria to produce short chain fatty acid. As a result intake and digestibility can again be limiting. To alleviate that however the supplement must also be cellulosic or fermented by the same bacteria as those fermenting straw.
There are many of these products about, to name but a few, brans are namely cellulosic, leaves from trees such as glyricidia jackfruit, leucaena etc. cottonseed cake also contain cellulosic energy. Some supplements such as tree leaves, has an excess of protein which when fermented yields ammonia. Young roadside grass can be an excellent supplement to straw diets something in any case farmers have routinely for years.
The correct supplement could possibly relieve both deficiencies as well as being utilized as a nutrient in its own right. The net result is that the responses to small amounts of the correct supplement can be much greater than expected as they help to utilize the basal feed better as well as being a nutrients themselves. Molasses however cannot be used for that purpose as it is fermented by a different microflora though it is often being used as a carrier for urea.
Livestock-crop interaction
I would like to complete this little article by a few comments on livestock-crop interaction. There is no doubt that excessive number of livestock can be destructive but in cropping areas this is seldom the problem. Livestock by consuming crop residues provide a large number of services as mentioned earlier and in many instances the manure is better fertilizer than the crop residues. I am reminded of the work in Sri Lanka by Pathirana (K.K.Pathirana, University of Ruhuna, Sri Lanka), who showed that by grazing cattle under coconut, coconut yields increased. By supplementing the cattle with straw and brans the cattle produced almost one calf/year and coconut yield increased still further.
Cattle grazing causes an increased rate of return of soil nutrients from bioareas to soil and thus increases soil fertility and coconut yield. There are no doubt a multitude of examples like that. Here however, people from industrialized countries have little to teach and much to learn.