The Energy Metabolism Of Ruminants

This book is intended to be a companion volume to 'Protein Nutrition in Ruminants' (1982, Academic Press), which emphasized both the role of proteins and new systems for their evaluation. Here the focus is on energy-yielding nutrients and problems involved in evaluating them. Nonetheless in both volumes there is explicit recognition of the interdependence of energy and protein nutrition. I have not attempted to review comprehensively all the literature relating to ruminant energy nutrition and must apologize to colleagues whose work is not fully reported. Where possible tables and figures are taken from the studies of our group at the Rowett Research Institute since, if for no other reason, I am most familiar with these data. I have first considered the nutrition of the newborn and have stressed the role of behaviour 'in determining whether nutrients enter or bypass the rumen. The development of the rumen, the of anaerobic fermentation and the roles of various principles . species of rumen bacteria, protozoa and fungi in relation to different substrates, are summarized. This is followed by accounts of the factors affecting the utilization of different substrates and the v vi Preface absorption and metabolism of the end-products of fermentation and digestion, together with estimates of digestive capacity in various segments of the gut. The ruminant's requirements for energy-yielding nutrients is considered in relation to the per formance of various activities and to environmental conditions, particular attention being paid to the requirement for glucose precursors.

Abstract: This book discusses the factors which affect the heat produced by animals and man and the ways in which the energy of the organic components of their diets are used to support growth and reproduction. The general thermodynamic principles are considered in addition to the physical principles related to heat loss by radiation, convection, conduction and evaporation of water. Major parts of the book deal with the minimal or basal production of heat, with the heat produced during muscular work and as a result of physiological reactions to the climatic environment. The test is intended for undergraduates and postgraduates who are studying energy metabolism in the context of zoology, agriculture, ecology, or medicine.

Two questions could not be avoided in the avant-propos of this book; (i) what is the importance to man of ruminant livestock, and (ii) what results of practical relevance in the growing mountain of scientific verbiage could be found in the Proceedings of this Symposium. Herbivores are an integral and critical part of the natural ecosystem which must be preserved because of their impact on human welfare. Wh at makes ruminants especially important to man is that they can thrive on fibrous forage and are thus the only viable enterprise over much of the earth's surface where crop growing is impracti cable. They contribute a wide array of products in addition to 50000 000 tonnes ofmeat (1977) and represent a 'capital reserve' that can be drawn upon in times of emergency: milk for example (450000000 tonnes) can make the difference between subsistence and starvation. About 60% of the world's meat and 80 % of the milk are produced by one third of the world ruminant population in the developed regions and as much as 99 % of the power for agriculture is provided by the ruminant population in developing countries. For the next two decades, a probable increase by 30 % for . cattle and buffalo and more than 40 % for sheep and goats is expected by improving health, fertility, nutrition and genetic potential rather than feed resources.

This volume is comprised of invited papers presented at the Seventh International Symposium on Ruminant Physiology, held in Sendai, Japan, in September 1989. Papers are invited on the recommendations of 300 international experts. The proceedings of this symposia provides the most comprehensive coverage available of current research in ruminant physiology.