Response in female fertility and calf growth to selection for pregnancy rate in tropical beef cattle
1993
Davis, G.P. | Corbet, N.J. | Mackinnon, M.J. | Hetzel, D.J.S. (Commonwealth Scientific and Industrial Research Organisation, Rockhampton (Australia). Div. of Tropical Animal Production) | Entwistle, K.W. (James Cook Univ., Townsville (Australia). Graduate School of Tropical Veterinary Science) | Dixon, R. (Commonwealth Scientific and Industrial Research Organisation, Townsville (Australia). Div. of Tropical Crops and Pastures)
Pregnancy rates were significantly higher in Bos indicus cross heifers of the High line compared with the Low line and in lactating 4-year-old cows and in 3 of the 5 years of the study. The Low line had significantly higher pregnancy rates in 1 year. These differences in pregnancy rates were reflected in weaning rates, but calf survival was only different between the lines in 2 of the 4 years analysed. The High line had significantly shorter days to calving than the Low line in heifers, lactating 3-year-old cows, non-lactating 3-year-old cows and lactating 4-year-old cows. Differences between the lines in pre-weaning growth varied according to generation with significantly lower weaning weights and pre-weaning growth in first generation High line calves from foundation dams and no differences between the lines in second generation calves from first generation dams. Post-weaning growth was significantly higher in High line calves. The results indicate that selection of sires on EBV for pregnancy rate leads to improved fertility in heifers and 4-year-old lactating cows without adverse effects on progeny growth.
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