Heterosis and heterosis retention for reproductive and maternal traits in Brahman - British crossbred cows



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Texas A&M University


Reproductive, maternal, and weight traits were analyzed for Angus (A), Brahman (B), and Hereford (H) straightbred cows; F1 and F2 BA and BH cows; and 3/8 B 5/8 A first (Bn) and second (Bn2) generation cows in Central Texas. Heterosis was estimated for calf crop born (CCB), calf crop weaned (CCW), and cow weight at palpation (PW) by linear contrasts within cow breed groups. F1 BA cows expressed heterosis (P<0.01) for CCB (0.10) and CCW (0.11), while F2 BA cows expressed negative heterosis (P<0.10) for CCB (-0.06) and CCW (-0.07). F1 BH cows expressed heterosis (P<0.001) for CCB (0.15) and CCW (0.16), and F2 BH cows retained F1 heterosis (P<0.001) for CCB (0.13) and CCW (0.15). Bn2 cows expressed heterosis (P<0.01) for CCB (0.14), but Bn cows did not express heterosis (P>0.10) for CCB or CCW. Only the F1 BA (22.9 kg) and F2 BH (42.1 kg) groups expressed heterosis (P<0.10) for PW. Bn2 cows (-65.7 kg) expressed negative heterosis (P<0.01) for PW. Heterosis for calf survival (CS), birth weight (BW), and weaning weight (WW) was estimated by linear contrasts within calf breed groups for B- and H-influenced calves. F1 BH (0.11) and F2 BH (0.14) calves expressed heterosis (P<0.01) for CS. None of the groups expressed heterosis (P>0.10) for BW, but B-sired F1 BH calves were 5.5 kg heavier (P<0.01) than H-sired F1 calves at birth. F1 BH (22.4 kg) and F2 BH (26.2 kg) calves expressed heterosis (P<0.001) for WW, and H-sired F1 BH calves were 20.7 kg heavier (P<0.10) than B-sired F1 calves at weaning.