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Description:
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Sire and family effects were evaluated for calf growth , udder and teat
conformation , and reproduction traits in 2 - to 4 - yr -old cows from the McGregor
Genomics Project . Cows were produced by embryo transfer (ET ) and natural service
(NS ) from the same 4 F1 Nellore -Angus sires , and were analyzed separately . Sire of cow
was significant for calf birth weight (P = 0 .014 ) among ET cows , but not NS cows .
Among NS families , calves from cows out of Brahman -Hereford dams were 2 .0 kg
heavier (P = 0 .064 ) at birth than calves from cows out of Brahman -Angus dams . Sire of
cow accounted for variation in weaning weight (P = 0 .006 ) and preweaning ADG (P =
0 .005 ) of calves from ET dams , but not NS dams . Family nested within sire also
accounted for variation (P = 0 .061 ) in weaning weights of calves from ET dams . Sire of
cow was significant for average teat length in ET (P < 0 .001 ) and NS (P = 0 .013 ) cows .
Sire of cow was significant for average teat diameter (P = 0 .022 ) among NS cows . Sire
of cow also affected udder support score (P = 0 .002 ) , cow disposition at calf birth (P =
0 .002 ) , and cow weight at weaning (P = 0 .045 ) in ET cows . Family and cow age also
accounted for variation in cow disposition at calf birth (P = 0 .015 , P = 0 .041 , respectively ) and cow weight at weaning (P = 0 .001 , P < .001 , respectively ) among ET
cows . Calf year of birth also affected (P < .001 ) cow weight at weaning among ET
cows . For NS dams , calf year of birth (P = 0 .012 ) , cow age (P < .001 ) , and parity nested
within cow age (P = 0 .005 ) affected cow weight at weaning . Although reproduction
data were not formally analyzed , there appear to be substantial differences for calving
rate and average calving date among these cow families . Data from this project will be
used for identification of genetic markers for these cow productivity traits . |