Somatic nutrient requirements of ruminants.

On the basis of existing information it is, perhaps, useful to propose tentative preliminary figures for somatic nutrient requirements (Table 2). Such a proposal may serve as a focus for research to clarify more precisely the somatic requirements for a given production function in a given species. The requirements, therefore, are presented as interspecies generalizations and are calculated per kilogram of metabolic body size for the maintenance of adult animals. Only those nutrients for which there are some experimental data are included, so the absence of a given nutrient is an indication that it has not been studied. The figure for energy was derived by subtracting from the metabolizable energy for maintenance those heat losses associated with bacterial action and with prehension and transport of food. The resulting value was then increased by an amount representing the relative inefficiency of VFA, as compared with glucose metabolism. Amino acid values are essentially those obtained by intravenous administration. Water-soluble vitamin values except for thiamin were not listed because they were not expected to differ from whole-body requirements. Thiamin data were based on the work of Mueller & Asplund (51). The most obvious need is for definitive values for the amino acid requirements for productive functions and for water-soluble vitamin data. In the absence of such data, experiments with supplementation of these nutrients will continue to be haphazard and arbitrary. (Table: see text).