A GENETIC EVALUATION OF PRODUCTION TRAITS FOR DAIRY CATTLE IN THAILAND

Abstract

A study of genetic parameters, breeding values, genetic and phenotypic trends, 305-day milk, fat and protein yields was carried out using 6,357 pedigree and milk records of Holstein Friesian crossbreds, recorded between 1990-2002, in the Master bull project database, Artificial Insemination Division. First lactations, with a lactation length of more than 150 days, were adjusted to a 305-day yield and Restricted, Maximum Likelihood (REML), estimated, variance components. Genetic parameters and breeding values were estimated using the Best Linear Unbiased Prediction (BLUP). The results showed that the average 305-day milk, fat and protein yields were 3,651.87 ± 904.97, 138.32± 39.98 and 117.42 ± 30.09 kg. respectively. Heritability of the three traits in the study was 0.33, 0.23 and 0.27 (single traits analysis) and was 0.32, 0.20 and 0.20 (Multiple traits
analysis). The genetic trend for milk production traits were constant or slightly decreased. When considering the genetic trends during 1990-2000, it was found that there was a slight increase (23 kg. /year, 0.6%/year) while the phenotypic trends were also increased. The average increase in phenotypic milk production was approximately 99.08 kg. /year (2.71%/year) while the phenotypic trends for fat and protein yield were similar to those for milk production.