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Description:
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Reproductive and weight traits were analyzed for Angus (A ) , Brahman (B ) ,
Hereford (H ) , and Nellore (N ) straightbred cows ; F1 NA cows ; 3 /8N 5 /8A cows and
quarter blood composite cows (BANH ) of the four straightbreds in Central Texas .
Heterosis was estimated for calf crop born (CCB ) , calf crop weaned (CCW ) , and calf
survival (CS ) by linear contrasts within cow breed groups . F1 NA cows expressed
heterosis (P < 0 .0001 ) for CCB (0 .22 ) and CCW (0 .20 ) . Except for the 3 /8N 5 /8Ac
cows , which resulted from the mating of NA bulls to 3 /4A 1 /4N cows , all of the
crossbred cow breed types expressed significant heterosis (P < 0 .05 ) when compared to
the weighted average of the parental purebreds for CCB . BANHc cows that were the
result of mating NA bulls to HB cows expressed heterosis for CCB (0 .35 ) (P < 0 .001 )
and CCW (0 .29 ) (P < 0 .05 ) . The 3 /8N 5 /8Aa females produced by mating 3 /4N 1 /4A
bulls to NA cows expressed heterosis (P < 0 .0001 ) for CCW (0 .20 ) . Heterosis for calf
survival was near zero for all breed types , but only two breed types of 3 /8N 5 /8A cows
were significantly greater than the weighted average of the parental purebreds . Heterosis
for birth weight (BWT ) and weaning weight (WWT ) was also analyzed by linear contrasts within cow breed groups . The BANHb and BANHc cows produced from
mating NA bulls to BH and HB F1 cows , respectively , expressed heterosis for BWT
(2 .89 + 0 .79 (P < 0 .001 ) and 3 .38 + 1 .51 (P < 0 .05 ) ) . All cow breed types expressed
significant heterosis (P < 0 .05 ) for WWT . The BANH2 cows resulting from the mating
of NA bulls to F2 HB or BH cows expressed heterosis (P < 0 .0001 ) for WWT (52 .01 kg
+ 9 .88 ) . |