Genetic evaluation for milk production traits in Slovakian Lacaune sheep

Abstract

Genetic parameters and covariance components as well as genetic and environmental trends were estimated for milk production traits in purebred Slovakian Lacaune sheep. The traits under study were daily milk yield, fat and protein content. The data from performance testing, gathered by the State Breeding Institute over the period 1999-2005 comprised 2196 test-day records. The pedigree data comprised 438 records. The three-trait animal model was used for the analysis. Genetic and environmental parameters were estimated using Restricted Maximum Likelihood (REML) algorithm as implemented in the VCE-5 package. The heritabilities were 0.15, 0.10 and 0.25 for daily milk yield, fat and protein content. Variance ratios for flock-test day effect as the most important environmental effect were 0.33, 0.47 and 0.21 for the respective traits. Breeding values used as the basis for estimation of genetic trends were calculated using best linear unbiased prediction (BLUP) methodology as implemented in the PEST package. Genetic trends were expressed as changes in averages of breeding values (adjusted for standardised 150-day lactation) across birth years of animals. Cumulative genetic changes over the analysed period were 5.1 kg, -0.16 and -0.12 % for 150-day milk, fat and protein content. Environmental trends were expressed as changes in averages of flock-test day solutions across years and months of the measurement. The maximum change between the two successive year-month periods was 0.47 kg for daily milk yield and 3.26 and 0.66 % for fat and protein content respectively.