Effects of mild inbreeding on productive and reproductive performance of Guernsey cattle.
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. Inbreeding ranged from 0 to 25.3% and averaged 4.1%. Milk and fat yields were all first lactations standardized to a mature equivalent, twice daily milking, and 305 d. Intrasire regressions of production traits on percent inbreeding were -23.8 kg of milk, -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 in inbreeding.
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D007178:Inbreeding; D007774:Lactation / Q000502:physiology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*