Effects of Mild Inbreeding on Productive and Reproductive Performance of Guernsey Cattle

Open Access
Publisher Website
Google Scholar
Abstract
Production and reproduction records that spanned a 24-yr period were used to study the effects of low coefficients of inbreeding in two experiment station Guernsey herds. In breeding ranged from 0 to 25.3% and averaged 4.1%. Milk and fat yields were all first lactations standardized to a mature equivalent, twich daily milking, and 305 d. Intrasire regressions of production traits on percent inbreeding were .sbd.23.8 kg of milk, .sbd.1.25 kg of fat, and .002% for fat percentage. Estimates of the effect of inbreeding on reproductive traits had large standard errors but suggested that inbreeding depressed reproductive performance. Age at first calving decreased 3.7 d per 1% increase inbreeding.