Evaluation of the growth performance of brown swiss, n'dama and brown swiss x n'dama crossbred genotypes in the humid tropics
Journal of Genetics and Breeding
Department of Animal Breeding and Genetics, College of Animal Sciences and Livestock Production, University of Agriculture, P.M.B.2240, Abeokuta, Nigeria; Department of Animal Science, University of Ibadan, Ibadan, Nigeria
Growth performance traits of 549 calves of different genotypes, from a long term crossbreeding programme in a dual-purpose (meat and milk) herd were studied. The effects of genotype (N'Dama, Brown Swiss, F1s, F2s, 25%, 62% and 75% Brown Swiss backcrosses), year of birth, sex and season on growth rate and body weight at birth, weaning and at 365day of age were studied along with estimated genetic parameters. Genotype significantly (P<0.05) affected the growth parameters studied. At birth, the Brown Swiss (BS) calves with average weight of 31.50kg were significantly heavier than the N'Dama calves and the various crossbred progenies. Among the crossbreds, F1s weighing 26.02kg were significantly heavier when compared with the F2s, 75%, 62% and 25% Brown Swiss. At weaning, there was no significant difference between average body weight of F1s and Brown Swiss calves, whereas the differences between the Brown Swiss calves and calves of other genotype groups became wider. The weight advantage of the F1s and the Brown Swiss calves was consistently maintained till yearling age at 365 days. A general heterotic advantage was observed among the crossbred progenies. Individual and maternal heterosis was positive for all traits. Mortality rate was highest among the 75% BS calves. The significant (P<0.05) effect of year of birth affected all growth traits. Calves born in the earlier years were significantly heavier than those born the latter years. The lowest birth weight was recorded in the year 1987, while the heaviest was recorded in 1974. Similar trend was observed at weaning. Calves average daily gains were linearly related to live weight at birth and at weaning. Season significantly (P<0.05) affected weight at birth and at weaning. Calves born in the early dry season (October-December) were heavier at birth and at weaning. The estimate of heritability and repeatability were moderately high. The genetic and phenotypic correlations were all positive ranging from 0.12 to 0.77.