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

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Abstract
Factors influencing reproductive performance and calf and dam live weights were examined for two indigenous breeds, Angoni and Barotse, and an introduced breed, Boran, under ranching conditions in Zambia.Over 5 years, 675 Angoni, 731 Barotse and 815 Boran records gave calving percentages of 82·5, 78·1 and 75·4 respectively. Year was an important influence on calving and weaning percentages in all breeds; age of dam had little effect 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 age and status did not influence calf weights, which were positively correlated with dam weights and negatively correlated with dam weight change during lactation.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 Barotses at 9 years. Subsequent calving rate was not influenced by live weight at the beginning of the breeding season nor, in lactating dams, by live-weight change between the autumn peak and mid breeding season.