Comparison of three methods for estimating breeding values of Mecheri rams for body weights

Estimates of breeding values were obtained for weights at birth, 3, 6, 9 and 12 months of age in Mecheri sheep maintained at Mecheri Sheep Research Station, Pottaneri, Tamil Nadu, India, over a period of 16 years (1991 to 2006). Records of 1763 lambs born out of 74 sires were used for the study. Analyses were carried out by least-squares (LS), best linear unbiased prediction (BLUP) and derivative free restricted maximum likelihood (DFREML) methods. Error variance for LS, BLUP and DFREML estimates were 0.153, 0.155 and 0.053; 3.573, 3.589 and 2.082; 6.529, 6.576 and 3.888; 8.697, 8.734 and 4.337 and, 8.324, 8.391 and 4.435 respectively for birth, 3, 6, 9 and 12 months weights. The coefficient of determination (R²) for LS, BLUP and DFREML methods were 24.7, 19.6 and 71.2; 32.6, 28.7 and 48.1; 37.0, 32.6 and 48.1; 39.0, 34.2 and 58.7 and, 46.9, 40.2 and 57.6 for birth, 3, 6, 9 and 12 months weights respectively. Spearman's rank correlation for DFREML with BLUP and LS estimates were highly significant (P<0.01). The DFREML method seems to be most efficient (lower error variance) and accurate (higher coefficient of determination) method. However, significant and higher magnitude of rank correlations between DFREML and LS showed that LS could be used as next best method.