Genetic trends for weaning weight during development of a multibreed population of beef cattle in two contrasting environments

Genetic trends for weaning weight were determined in two herds of multibree d beef cable that originated from a common base and were subject to mutual breeding policies in separate environments. The herds diverged for the dire ct though not the maternal genetic component of weaning weight within the 1 3-yr period examined; in the final year, the difference (P < 0.001) between the herds was almost 3 kg. This could have been partly due to unequal sele ction differentials and generation intervals. Results suggested the extent of natural selection also differed between the two environments.