Estimates of genetic, environmental and phenotypic trends in indigenous Nguni cattle of Zimbabwe: implication for manage
Journal Title: Scientific Journal of Animal Science - Year 2013, Vol 2, Issue 12
Abstract
Growth traits in indigenous cattle are desirable economicparameters which should be improved and their trends monitored over time toinvestigate direction of change. Traits considered were birth weight (BWT) andweaning weight (WWT). BLUP breeding values were regressed on year to obtainannual direct and maternal genetic trends, while fixed effects solutions andmean performances were regressed on year to obtain environmental and phenotypictrends, respectively. Linear regression representing genetic trends for directeffects indicated a decrease of -0.02 kg per year for BWT, and an increase of0.12 kg per year for weaning weight. The environmental trend was positive forbirth weight and negative for weaning weight. A cubic regression produced arelative better fit for environmental values for WWT (R-square= 34%), ascompared to a linear regression of (R-square=18%). Environmental values for WWTdecreased from approximately 1983, suggesting that the environmental conditionshad a negative effects on WWT. There was a net phenotypic gain for birth weightof 0.48 kg per year, and a net phenotypic loss for WWT of -01.57 kg per year. The trend of maternal ability forBWT increased at the first quarter of the study (1983 to 1991), and thendeclined thereafter (1992 to 1997), and was insignificant for WWT. The resultsobtained in the present study on various trends demonstrate that very smallgenetic gains were realized signaling need for change in selection and/ormanagement procedure in the scheme.
Authors and Affiliations
N. Assan| Matopos Research Station, Bag K 5137, Bulawayo, Zimbabwe.
Keywords
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- EP ID EP670
- DOI 10.14196/sjas.v2i12.1089
- Views 506
- Downloads 22
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