Genetic studies of fertility performance in Holstein-Friesians

Abstract

A dairy herd of Holstein-Friesian purebred was eyaluated for its fertility in over 20 years. A least square mean of 40.7±0.5 months was found for age at first calving (AFC). This estimate is longer by about 10 months than the available estimate of same cattle breed kept in the tropics. Variation of AFC due to sire was not significant but variation was significant over the years; as it has increased by about 500 days over the 20 years. Regression revealed that AFC has increased significantly by 25.0 daysl year. Least square mean for calving interval (CI) was 455.5±9.2 days. This estimate again is'Jonger by about 60 days than the available values of same cattle breed in the tropics. Variation of this trait was significant due to sire, Parity, dam within same sire and due to year. Regression gave a 4.5 days increase of CI/ year. This implies that CI has increased by about 90 days over the 20 years. Heritability estimates of age at first calving and calving interval were 0.15±0.1 and 0.18±0.1 respectively.