Lifetime productivity of crossbred cows, 2. Age and weight at first oestrus, calf birth weight, assisted calvings, calving interval and reproduction rate
1991
Newman, S. (Adelaide Univ., Glen Osmond (Australia). Waite Agricultural Research Inst.) | Deland, M.P. (South Australian Dept. of Agriculture, Naracoorte (Australia). Struan Research Centre)
Crossbred heifers were produced from 7 breeds of cattle by mating Hereford bulls to Shorthorn cows, Hereford bulls to Friesian cows, Hereford bulls to Jersey cows, and using semen or natural service of Sahiwal, Charolais, Simmental and Brahman bulls on Hereford cows. Breed differences were important sources of variability for age and weight at first oestrus. The heifers were joined with Hereford bulls to produce backcross progeny in a semi-arid environment. Parity and its interaction with breed had significant effects on frequency of assisted calvings, birth rate, calving rate and weaning rate. On average, over all parities, European cross dams had calves of higher birth weight than other types but also had more assisted calvings, a lower calving rate and longer calving interval.
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