Quantitative animal nutrition and metabolism: a general review

Abstract

Examples of increasing productivity of livestock enterprises over the last three to four decades, and the contribution to such advances, of scientific knowledge including that of the nutrition of farm livestock are referred to. Space limitations neccessitate restricting the review to consideration of ruminant livestock, with particular emphasis on ruminant digestive processes, on milk synthesis and on certain aspects of energy metabolism. Factors affecting the supply of amino acids to the host animal are referred to. The importance of synchronising N and energy supply to the rumen microorganisms to maximize microbial protein synthesis is emphasised and the need for knowledge of the extent to which particular feed proteins escape fermentation within the rumen. Concerning milk synthesis, the importance of an adequate supply of glucose or glucose precursors is mentioned as are the causes of the low milk fat syndrome. Limitations to existing knowledge of amino acid supply and milk protein synthesis are noted. Finally, aspects of ruminant energy metabolism studies are considered; particular stress is given to the importance of energy transactions in the intestinal wall as a major contributor to overall heat increment.