Genetic improvement in lifetime milk yield expected from selection on single traits or indices

Performance records of 1 647 Murrah buffaloes from 4 military dairy farms were analysed to study relationships between early and lifetime performance traits and to compare genetic gains in lifetime milk yield expected from selection on an individual early economic traits or in combination in Murrah buffaloes. The phenotypic correlations of first lactation milk yield, MY/FLL and MY/FCI with lifetime milk yield and milk yield/day of herdlife were positive and significant, The corresponding genetic correlations were also positive and high (0.59+/-0.15 to 0.91+/-0.08) suggesting that continued selection on first lactation milk yield is an efficient means of maximising lifetime milk yield and milk yield/day of herdlife. The phenotypic correlations of early economic traits with longevity were, in general, low and ranged between -0.09 to 0.18. The corresponding genetic correlations were not significantly different from zero. The expected responses to different selection criteria revealed that the correlated response in lifetime milk yield was more than the direct response when selection was based on MY/FLL. Combination of early economic traits did not lead to any appreciable improvement in correlated response. These results therefore suggested that there was no advantage in basing selection on combining various early economic traits and that MY/FLL wan an ideal trait for selection to achieve maximum gain in lifetime milk yield.