Reproduction in continuously underfed Brahman cows

Abstract

AbstractThis experiment examined the effects of sustained levels of undernutrition applied to grazing Brahman heifers on subsequent lifetime reproductive performance. Weaned heifers were raised to a target weight of 270 kg at three different stocking rates to obtain contrasting weight gains (0·097 kglday, L = low; 0·215 kg/day, M = medium; 0·259 kg/day, H = high). They were then subjected to common grazing in a low-quality Brachiaria humidicola pasture, where mean weight changes ranged between -0.100 and +0·300 kg/day depending upon season and physiological condition. Differences in age at first calving between L and the other treatments (200 days) were maintained in subsequent calvings. Calf weaning weights were higher in L and M than in H. The mean weight of calf weaned per cow per year was higher in M than in either L of H. Cow weight at conception increased with parity, and was higher in L than in the other treatments. Similar trends were observed for the dam's weight preand post calving, and at weaning. This trend was associated with higher weight loss during lactation in I..We conclude that in tropical grazing systems that allow only low growth rates, differences established early in reproductive life may become perpetuated for the lifetime of the animal. Management implications in the context of extensive tropical grazing systems are discussed.