Estimation of Genetic and Environmental Trends from Simultaneous Genetic Evaluation of Bulls and Cows using Hokkaido Dairy Herd Milk Records

Abstract

The purpose of this study is to estimate genetic and environmental trends for milk and fat production and to investigate the effective breeding program in Hokkaido. All lactation records of 757, 615 Holstein cows in 10, 553 herds were used in this study. These records were obtained from Hokkaido Dairy Herd Milk Recording Association. Breeding values were estimated from simultaneous evaluations of bulls and cows using the animal model. Environmental trends were estimated from averages of herd-year effects in mixed model. Annual environmental changes from 1982 to 1988 in the year of calving were 136.8kg and 5.20kg for milk and fat production, respectively. Genetic trends in the year of calving were estimated from averages of cows' breeding values and averages of sires' estimated transmitting abilities weighted by number of daughters. Annual genetic changes from 1982 to 1988 in the year of calving were 73.2kg and 2.50kg for milk and fat production, respectively. Genetic trends in the year of a cow's birth were estimated from averages of cows' breeding values. Annual genetic changes in the year of a cow's birth for cows' breeding values were 88.1kg and 3.15kg from 1981 to 1986 for milk and fat production, respectively. Genetic trends in the year of a bull's birth were estimated from averages of bulls' breeding values. Annual genetic changes in the year of a bull's birth for bulls' breeding values were 82.1kg and 2.34kg from 1979 to 1984 for milk and fat production, respectively.