| Popis: |
Milk production, feed consumption and body weight data were collected on 661 lactations of 318 Holstein cows by 17 sires to study the genetic aspects of gross feed efficiency of milk production. Gross feed efficiency was defined as the ratio kilogram of fat-corrected milk yield per therm of estimated net energy consumed. Least squares analyses of variance were conducted on both a first and over-all parity basis. Body weight change from calving to the end of lactation had a significant effect on efficiency in both analyses. Year effects on efficiency were not significant in the first parity, but were on an over-all lactation basis. The genetic correlations between efficiency and production, efficiency and body weight, and body weight and production were 0.92, −0.17, and 0.28, respectively. The heritability of efficiency was 0.46 as opposed to 0.62 for production. It was concluded that selection on the basis of yield alone would increase the genetic potential for feed efficiency. |
