Ingestion rates, food utilization and turnover of water and sodium in grazing buffaloes, Bubalus bubalis, and cattle, Bos taurus × B. indicus, in monsoonal Northern Territory

Abstract

Cows and steers of swamp buffalo and Brahman x Shorthorn cattle grazing freely in a paddock of pangola grass pasture during a monsoonal dry season were compared over 14 days in body composition, rates of sodium and water turnover, and rates of food ingestion by using the isotope dilution method. The cattle, especially the steers, had a higher proportion of body solids than the buffalo and appeared to have a higher proportion of body fat. There were significant interactions of species with either sex, castration or both in the proportions of body water and solids. The differing body compositions had a marked influence in comparisons of physiological rate parameters between the buffalo and cattle. The buffalo had higher rates of water turnover than the cattle and the two species had similar rates of sodium turnover when standardized for body size and composition. The rates of food consumption of the buffalo and cattle were significantly different when expressed per animal and expressed relative to metabolic body mass, with greater rates in the buffalo. When the influence of differing body compositions was removed, the rates of food consumption were not significantly different between species but approached significance. The species showed similar rates of mass gain but the cows of both buffalo and cattle had greater rates than the steers. The conversion efficiency of food to body mass was not statistically different between buffalo and cattle, but the composition of the respective increments may have differed, possibly by different proportions of protein and lipid. This is discussed with respect to the relative efficiencies of nitrogen conservation in buffalo and cattle. It is concluded that buffalo and cattle have different water physiology and broadly similar nutritional efficiencies. The performances of the two species in the monsoonal tropics differ for ecological reasons ensuing from different behavioural adaptations and water physiology.