| dc.description.abstract | 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. | en |
