Review Lecture: The nutrition of ruminant animals in relation to intensive methods of agriculture

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Intensive methods of nutrition and husbandry of sheep and cattle are being developed and accepted by the farming community largely as a result of economic pressures. Some are briefly described, notably intensive methods of beef production based on all-grain feeding and intensive methods of lamb production based on alterations of the breeding cycle of ewes by control of day length. The microbiology, physiology and biochemistry of ruminal digestion when grains rather than roughages form the diet are described and some of the new problems that have arisen and their causes are discussed. These include parakeratosis of the rumen wall, abscess formation in the rumen due to ingested hairs, deposition of body fats containing unusual amounts of fatty acids with branched chains and straight chain acids with an uneven number of carbon atoms, incidence of zinc deficiency and enhanced vitamin A requirements. New possibilities, including novel methods of feeding and diet preparation in relation to protein utilization by ruminants and control of the ruminal fermentations are considered. Some of the wider implications of these advances in terms of human food production, present limits on animal productivity, and natural resource utilization are discussed.