Genetic and non-genetic parameters of replacement rate component traits in Holstein Friesian cattle

Records on 3092 pregnancies distributed over a period of 24 years (1986 to 2010) were used to estimate genetic and non genetic parameters of threshold traits in Holstein Friesian. Parity, season and year of calving were included in the model to estimate their effect on replacement traits. A total of 105 sires' records were used to study the genetic component of the characters. The overall averages for abnormal and normal births, male-female sex ratios, mortality and culling rate in females up to age at first calving and female replacement rates based on female births and total pregnancies were estimated as 12.0% and 88.0%, 52.5% and 47.5%, 23.0% and 7.0% and 70.0% and 29.0% respectively. The effects of parity and year of calving on above traits were found to be significant, except parity effects on culling rate and replacement rate based on total pregnancies, which were non-significant. The season effects for all traits were non-significant. Average 3.45 pregnancies were required to produce one heifer that becomes replacement of the old and low producer cow. The heritability culling and replacement rate from total pregnancy were 0.71 and 0.66 suggesting sufficient additive genetic variance for selecting sires in these traits. Better feeding and health management could reduce mortality and force culling female calves.