Genetic Parameters of Milk Yield from Three Consecutive Lactation Periods of Imported Holstein Cows

摘要

Both genetic and environmental factors contribute to the phenotype. The contribution of each factor depends on the genetic architecture of the trait and the environment in which an individual is exposed. We present how the genetic contributions of milk yield vary in imported Holstein cows during three periods of lactation. Data were collected from Indonesian Holstein breeding center at Baturraden, Central Java (BBPTU-HPT Baturraden). The information contained pedigree and milk yield records standardized for 305 days from three lactation periods of cows imported in 2012. In total 133 animals were recorded in the pedigree, 57 cows with lactation records from 19 families were used in the Half-sib family analysis. We employ ANOVA with sire as a factor to estimate the genetic and environmental variance. Results showed that milk yield differed among lactation periods which were 5750, 4749 and 4190 kg whereas the heritability were 0.32, 0.42 and 0.63 for lactation one, two and three respectively. The decrease in milk yield on lactation 2 and lactation 3 were assumed to be the consequences of adaptation towards new environment. The different heritability values among lactations as trade-offs between adaptability and production ability involving different genetic architecture among lactation periods and environmental changes. Different sets of genes might govern milk yield in different lactation periods; and different environments contribute differently to the traits. More thorough analysis using mixed model incorporating fixed-environmental and genetics effect with the possible inclusion of genetic by environment interaction might give more proper explanation of this phenomenon.