REPRODUCTION IN CONTINUOUSLY UNDERFED BRAHMAN COWS

This experiment examined the effects of sustained levels of undernutri tion applied to grazing Brahman heifers on subsequent lifetime reprodu ctive performance. Weaned heifers were raised to a target weight of 27 0 kg at three different stocking rates to obtain contrasting weight ga ins (0.097 kg/day, 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 B rachiaria humidicola pasture, where mean weight changes ranged between -0.1.00 and +0.300 kg/day depending upon season and physiological con dition. Differences in age at first calving between L and the other tr eatments (200 days) were maintained in subsequent calvings. Calf weani ng weights were higher in L and M than in H. The mean weight of calf w eaned per cow per year was higher in M than in either L of H. Cow weig ht at conception increased with parity, and was higher in L than in th e other treatments. Similar trends were observed for the dam's weight pre- and post calving, and at weaning. This trend was associated with higher weight loss during lactation in L. We conclude that in tropical grazing systems that allow only low growth rates, differences establi shed early in reproductive life may become perpetuated for the lifetim e of the animal. Management implications in the context of extensive t ropical grazing systems are discussed.