Evaluation of heterosis and heterosis retention in Bos taurus-Bos indicus crossbred cattle for reproductive and maternal traits in cows
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Reproductive, maternal and weight traits were analyzed for Angus (A), Brahman (B), Hereford (H), and Nellore (N) straightbred cows; F1 NA; 3/8N 5/8A cows; and four breed composite cows (BANH) at the McGregor Research Station in Central Texas. Heterosis was estimated for calf crop born (CCB) (n = 1,698), calf crop weaned (CCW) (n = 1,698), calf survival (CS) (n = 1,388), birth weight (BW) (n = 1380), weaning weight (WW) (n = 1,198), and cow weight at palpation (PWT) (n = 1,929) by linear contrasts for cow breed and cow breed group. F1 NA and the quarter breed composite BANH dam group expressed significant (P < 0.0001) heterosis for calf crop born and calf crop weaned. The 3/8 N 5/8 Aa produced by matings of 3/4 A 1/4 N bulls to NA dams expressed significantly more heterosis for CCB (P < 0.0001) and CCW (P < 0.01), while the 3/8 N 5/8 Ac dams expressed less heterosis than predicted from the dominance model for both traits. For CS the 3/8 N 5/8 Aa expressed the same amount of heterosis as predicted from the dominance model of 0.05, while the 3/8 N 5/8 Ab and 3/8 N 5/8 Ac dams expressed less heterosis than predictions based on the dominance model. Heterosis estimates were only significantly higher (P < 0.10) for BANHb dams than expectations from the dominance model. For BW all the BANH cows expressed significant heterosis except for the BANH2 cows which expressed significant (P < 0.05) negative heterosis of -0.96 kg. Calves out of F1 NA cows were heaviest at weaning with 239 kg. All BANH cows expressed significant (P < 0.0001) heterosis for weaning weight except for the BANHc cows. These heterosis estimates were higher than those expected from the dominance model for BANHb and BANH2 cows, while the heterosis estimate was slightly lower in BANHa cows and similar for BANHc cows. All 3/8 N 5/8 A cows expressed less heterosis for WW than prediction from the dominance model. Nellore cows were the heaviest at four years of age with 542 kg. Only the BANHb and BANHc cows expressed significant (P < 0.05) heterosis for PWT. None of the 3/8 N 5/8 A cows expressed heterosis for cow weight at palpation. Results from this study showed that heterosis levels expressed by the different crossbred cow types were generally equal or higher to those predicted by the dominance model.
Neufeld Arce, Rodney Oliver (2006). Evaluation of heterosis and heterosis retention in Bos taurus-Bos indicus crossbred cattle for reproductive and maternal traits in cows. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from