GENETIC AND PHENOTYPIC CORRELATIONS BETWEEN LINEAR TYPE TRAITS AND MILK YIELD IN SAHIWAL COWS

The traits of economic importance in farm animals are mostly controlled by many gene pairs and hence show correlations. The knowledge of such correlations is very much needed while making multiple traits selection in farm animals. The present study was planned with the objectives to find out genetic and phenotypic correlations between linear type traits and milk yield in Sahiwal cows. Freshly calved 310 cows were scaled and scored for traits on a linear scale of 1-9 following the guide lines of International Committee on Animal Recording. The variance and covariance components were estimated using residuals or restricted maximum likelihood (REML) procedures. The linear mixed model was fitted for estimation of variance. Bivariate animal model analysis was performed for estimation of genetic and phenotypic correlations. Stature, angularity, rear udder height, fore teat length, dewlap width, foot angle, udder depth and rear udder width were significant sources of variation for score-day milk yield (P<0.05-P<0.001). The 305-day milk yield was influenced by linear type traits of rump angle, rump width, central ligament and rear udder width (P<.05-P<.001). Highest positive genetic correlations were for rear udder width with score-day milk yield (0.43 +/- 0.00) and 305 days milk yield (0.40 +/- 0.00). The highest negative genetic correlation (-0.27 +/- 0.00 and -0.23 +/- 0.00) was found of udder depth with score-day milk yield and 305-day milk yield. The phenotypic correlations ranged from -0.23 +/- 0.06 between udder depth and score-day milk yield to 0.54 +/- 0.04 between rear udder width and score-day milk yield. The genetic and phenotypic correlations will help to short list the type traits and put focus on those that are more important. The linear scoring in Sahiwal cattle should be initiated at public and private farms.