Genetic and phenotypic parameters for lactation traits in a flock of Saanen goats in Mexico

Heritability, repeatability and genetic and phenotypic correlations of total milk production (TM), cumulated milk production to 120 days (M120) and lactation length (LL), were estimated from the analysis of 1413 records (566 does) obtained from a Saanen goat flock in Querétaro, Mexico, during 1991–1997. Variance components were estimated using a restricted maximum likelihood procedure and applying an animal model. The model included the fixed effects of year–season of kidding, litter size and age of doe, and random effects of animal, permanent environment and residual. For TM, M120 and LL estimates of heritability were 0.22 ± 0.07, 0.12 ± 0.05 and 0.04 ± 0.03, and of repeatability were 0.40, 0.27 and 0.11, respectively. Genetic correlations between TM and M120, TM and LL, and M120 and LL, were 0.98, 0.58 and 0.53, respectively. Phenotypic correlations ranged from 0.30 to 0.83. The correlated selection response for TM from indirect selection on M120 was 71.5% of that expected from direct selection. Efficient selection for TM is possible and M120 could be used as an early indicator of TM, due to the high indirect selection response calculated.