I.L. Mao

Changes in body weight and frame and its genetic variation during the productive life of dairy cows

Abstract Data used were body weights and physical measures on hip height, body depth, chest girth, hip width, and body length taken at an experimental dairy herd of three breeds (Holstein, Jersey and Danish Red). Random regression mixed models were used to evaluate changes in variances through the productive life of dairy cows in body weight and in each of the physical measures. To indicate the frame size of a cows body, a frame index was established based on linear physical measures, which was a simple cross-product of body depth by hip width. Further analyses with a random regression mixed model indicated that the changes in the index values over age reflect well the process of growth, and were only marginally affected by stages of lactation. Frame index and body weight were highly correlated. However, if breeding for frame size was desired, the frame index would be a preferred selection criterion over the more conventional criterion of body weight, because body weight measures were affected equally by growth and body condition.