GENETIC AND PHENOTYPIC CORRELATIONS AMONG PRODUCTION AND REPRODUCTIONTRAITS IN AFRINO SHEEP

Knowledge of genetic correlations among traits is essential for derivi ng a selection strategy for any breed. In this study, genetic and phen otypic correlations were estimated among weaning weight (WW), nine- (W 9) and 18-month body weight (W18), clean fleece weight (CFW), mean fib re diameter (MFD), total weight of lamb weaned over three parities (TW W), as well as number of lambs born (NLB) and weaned (NLW) over three parities in the Carnarvon Afrino flock. Covariance components and gene tic correlations were estimated using DFREML procedures. High genetic (0.915 to 0.980) and phenotypic (0.643 to 0.809) correlations were est imated among WW, W9 and W18. There were no significant genetic correla tions between CFW and WW, W9 or W18, while the corresponding phenotypi c correlations were 0.148, 0.143 and 0.095, respectively. Mean fibre d iameter was neither genetically nor phenotypically significantly corre lated with WW, W9 or W18, the estimated phenotypic correlations being close to zero. Low positive genetic (0.175) and phenotypic (0.163) cor relations were estimated between CFW and MFD. High significant genetic (0.828 to 0.998) and phenotypic (0.791 to 0.920) correlations were ob tained among the reproduction traits. High positive genetic correlatio ns 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 mode rate negative. A negative genetic correlation of -0.523 was estimated between CFW and TWW. The results of this study imply that TWW, which i s very important, but sex limited as well as a laborious and time-cons uming measurement, can be improved by indirect selection for body weig ht at any age.