Genetic and phenotypic correlations among production and reproduction traits in Afrino sheep

Author: M.A. Snyman, G.J. Erasmus and J.B. van Wyk, J.J. Olivier
Year: 1998
Issue: 2
Volume: 28
Page: 74 -

Knowledge of genetic correlations among traits is essential for deriving a selectionstrategy for any breed. In this study, genetic and phenotypic correlations were estimated among weaning weight (WW), nine- (W9) and 18-month body weight (W18), clean fleece weight (CFW), mean fibre diameter (MFD), total weight of lamb weaned over three parities (TWW), as well as number of lambs born (NLB) and weaned (NLW) over three parities in the Carnarvon Afrino flock. Covariance components and genetic correlations were estimated using DFREML procedures. High genetic (0.915 to 0.980) and phenotypic (0.643 to 0.809) correlations were estimated among WW, W9 and W18. There were no significant genetic correlations between CFW and WW, W9 or W18, while the corresponding phenotypic correlations were 0.148, 0.143 and 0.095, respectively. Mean fibre diameter was neither genetically nor phenotypically significantly correlated with WW, W9 or W18, the estimated phenotypic correlations being close to zero. Low positive genetic (0.1 75) and phenotypic (0.163) correlations were estimated between CFW and MFD. High significant genetic (0.828 to 0.998) and phenotypic (0.791 to 0.920) correlations were obtained among the reproduction traits. High positive genetic correlations of 0.752, 0.768 and 0.892 were estimated between TWW and WW, W9 and W18 respectively. The corresponding phenotypic correlations were low positive (0.127, 0.238 and 0.264). The estimated genetic correlations of MFD and CFW with the reproduction traits were generally low to moderate negative. A negative genetic correlation of -0.523 was estimated between CFW and TWW. The results of this study imply that TWW, which is very important, but sex limited as well as a laborious and time-consuming measurement, can be improved by indirect selection for body weight at any age.

Keywords: body weight, fleece traits, Genetic correlations, Reproduction traits, sheep
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