Genetic and environmental influences on beef cattle production in Zambia. 3. Carcass characteristics of purebred and reciprocally crossbred castrated males

Carcass characters for 365 male castrated cattle of the Africander, Angoni, Barotse and Boran breeds, and the reciprocal crossbreds of the latter three were reported. In each of the two year-of-birth groups, different slaughter-age/management regimes were used. For all carcass characters except those related to size, the two Sanga breeds, Africander and Barotse, were very similar, as were the two zebu breeds, Angoni and Boran. The introduced breeds, Africander and Boran, which had similar carcass weights, had heavier carcasses (+18 kg, +10%) than the indigenous Barotse and Angoni breeds. The Sanga breed carcasses had less fat cover than those of the zebu breeds. Maternal effects were not important for carcass characters and the Angoni/Barotse and Angoni/Boran crosses showed no heterosis. In the Barotse/Boran crosses, slaughter and carcass weights and eye muscle area gave between 8% and 9.5 heterosis, and the linear carcass measurement between 2% and 3%. There was no economic advantage in delaying slaughter to the later of the two ages compared in the two year-of-birth groups

Genetic and environmental influences on beef cattle production in Zambia. 4. Weaner production from purebred and reciprocally crossbred dams

Dam reproductive performance of purebred Africander, Angoni, Barotse and Boran, and reciprocal crossbreds of the latter 3 breeds under ranching conditions were investigated. Mean performance based on a maximum of 1996 records collected over six parities were: calving rate, 65.6%; weaning weight rate, 62.8%; calf birth weight, 26.6 kg; calf weaning weight, 163.6 kg; and dam live weight at weaning 363.0 kg. Comparative evaluations of dam performance indicated that there were no differences between reciprocal crossbred dams for calving and weaning percentages; dam status at mating had an important effect on fertility; there were large differences between breeds for calf weights but heterosis estimates were small and non-significant; there were no differences between progeny weights of reciprocal crossbred dams; dams which lost most live weight during the breeding season had significantly poorer fertility. Sex, date and period of birth, and dam status had significant effects on calf weight. Overall estimates of heritability derived by dam/daughter regression were 0.20 for calving percentage, 0.76 for calf birth weight and 0.72 for weaning weight

Genetic and environmental influences on beef cattle production in Zambia. 1. Factors affecting weaner production from Angoni, Barotse and Boran dams

Factors influencing reproductive performance of Angoni, Barotse, and Boran under ranching conditions are examined. Five years reproduction records of 675 Angoni, 731 Barotse and 815 Boran were analysed. Calving percentages were 82.5, 78.1 and 75.4 for Angoni, Barotse and Boran, respectively. Year had significant influence on calving and weaning percentage in all breeds. Age of dam and status at mating was only important in the Angoni breed, in which lactating dams produced more calves than dry dams. Mean calf-weaning weights were 147.3, 167.0 and 169.5 kg for the Angoni, Barotse and Boran dam breeds respectively. Hereford, Friesian and Boran bulls sired heavier progeny than Angoni and Barotse. Dam live weights at the beginning of the breeding season were 313, 357 and 348 kg for the Angoni, Barotse and Boran breeds respectively. Angoni and Boran dams reached maximum live weight at 7 years and Barotse at 9 years

Genetic and environmental influences on beef cattle production in Zambia. 2. Live weights for age of purebred and reciprocally crossbred progeny

Live weights from birth to 3.5 years are reported for beef cattle reared under ranching conditions in Zambia. The 809 cattle were purebred Africanders, Angonis, Barotses and Improved Borans and the reciprocal crossbreds of the latter three breeds born in 2 years. All animals born in the 1st year and half the males born in the 2nd year grazed natural grassland. The remaining males and all females born in the 2nd year received, in addition, dry season supplementary feed from 1.5 years of age. The interaction of genotype with year-of -birth was important but not the interactions of genotype with management or sex. Purebred progeny of the introduced Africander breed were heavier than the progeny of the indigenous Angoni and Barotse breeds in both year-of-birth groups, but only heavier than progeny of the introduced Boran breed in the first group. On average, the Africander progeny had live-weight advantages of about 16% and 10%, and the Boran progeny advantages of about 12.5% and 5.5% over the purebred Angoni and Barotse progeny respectively. Heterosis estimates tended to increase with age, reaching levels of about 5 to 6% in the Barotse/Boran crosses at and after 1.5 years. Heterosis was not shown by the other crosses. The Barotse and Boran breeds had similar maternal effects which were superior to those of the Angoni breed