Gladney, Cody Jack (2008-08). Evaluation of udder and teat characteristics, calf growth, and reproduction in young Bos indicus-Bos taurus cows. Master's Thesis.
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.