Study of the estimation of realised genetic gain in dairy performance characters from trends in bull breeding values. 1. Estimation of realised genetic gain using several daughter age classes
Kretzschmar, B.; Clausing, P.
Archiv fur Tierzucht 20(5): 295-312
1977
Document Number: 528973
32 674 first-lactation records obtained between 1 Jan. 1967 and 31 Dec. 1971 for German Black Pied heifers in 58 sire groups were analysed for genetic trend using (1) the general regression model given by Smith [see ABA 30, 1990], (2) the av. regression of breeding value on year, and (3) a weighted regression procedure. The 3rd method had the smallest bias. The estimated values for genetic gain/yr over the 5 yr were 21.69 kg for milk yield, 0.009% for fat content and 1.14 kg for fat yield.