The Level of Inbreeding and Its Effects on Milk Yield, Age at First Calving and Calf Mortality in Holstein Cattle Reared on the Agricultural Faculty Farm of Ege University
In this study, the inbreeding coefficient of 1535 Holstein calves born on the Agricultural Faculty farm of Ege University during the period 1980-2000 was calculated, and the change of inbreeding levels over the years was investigated. Furthermore, the effects of inbreeding on first lactation 305-day milk yield, age at first calving and calf mortality were examined. The mean inbreeding level of calves born in the investigated period was 1.89%. The level of inbreeding in the herd fluctuated from 0% to 4.37% according to the birth years of calves. Furthermore, over the last 3 years of the period (1998-2000) inbreeding steadily increased. Over the years, it was estimated that a linear relationship (R2 = 0.62) existed between the inbreeding level and the percentage of sires bred in the herd. Estimates of inbreeding depression per 1% increase in inbreeding were -16.9 kg for milk yield, and 2.8 days for age at first calving. These levels of depression, however, were not statistically significant. A significant relationship between inbreeding and calf mortality was found. While calf mortality for non-inbred calves was 8.9%, it was 17.8% for calves with an inbreeding level ? 12.5%.
The Level of Inbreeding and Its Effects on Milk Yield, Age at First Calving and Calf Mortality in Holstein Cattle Reared on the Agricultural Faculty Farm of Ege University
In this study, the inbreeding coefficient of 1535 Holstein calves born on the Agricultural Faculty farm of Ege University during the period 1980-2000 was calculated, and the change of inbreeding levels over the years was investigated. Furthermore, the effects of inbreeding on first lactation 305-day milk yield, age at first calving and calf mortality were examined. The mean inbreeding level of calves born in the investigated period was 1.89%. The level of inbreeding in the herd fluctuated from 0% to 4.37% according to the birth years of calves. Furthermore, over the last 3 years of the period (1998-2000) inbreeding steadily increased. Over the years, it was estimated that a linear relationship (R2 = 0.62) existed between the inbreeding level and the percentage of sires bred in the herd. Estimates of inbreeding depression per 1% increase in inbreeding were -16.9 kg for milk yield, and 2.8 days for age at first calving. These levels of depression, however, were not statistically significant. A significant relationship between inbreeding and calf mortality was found. While calf mortality for non-inbred calves was 8.9%, it was 17.8% for calves with an inbreeding level ? 12.5%.
