Estimation of phenotypic and genetic parameters for pre- and post- weaning performance in nili ravi heifers

The data on pedigree and body weights at different ages of 624 buffalo heifers kept at the Livestock Experiment Station, Bahadurnagar, Okara were collected from 1989 to 2002 in the present study and analyzed by using computer programs LSMLMW (Mixed Model Least square and Maximum Likelihood) and DFREML (Derivative Free Restricted Maximum Likelihood Model) to investigate the genetic and phenotypic parameters of birth weight, weaning weight, yearling weight, pre-weaning average daily gain, post-weaning average daily gain and weight up to three years of age. Overall average birth weight for Nili-Ravi female calves was 35.86 plus minus 4.30kg with coefficient of variation 11.99%. Average weaning weight of Nili-Ravi female calves was 66.12 plus minus 9.16 with coefficient of variation 13.85 %. Average yearling weight was found to be 145.82 plus minus 19.50 with coefficient of variation 13.37%. Pre-weaning average daily gain was 316.17 plus minus 18. 33 g, while average post-weaning daily gain was 301.21 plus minus 29.14 g. Average weight at 2 years of age in heifers was 240.05 plus minus 25.10 kg and average 3 years weight was 329.73 plus minus 23.17 kg. The analysis of variance for influence of year and season of birth, age and weight of dam at calving on weights of calve at different ages indicated that all the factors, year and season of birth, age and weight of dam significantly effected the birth weight, weaning weight and pre-weaning daily gain. However all the other weights and gains were significantly affected by year and season of birth and weight of the dam but generally by the all above factors. Maximum weights and gains were observed in spring season, while minimum gains were obtained in autumn, humid hot, dry hot and winter seasons. In case of genetic parameters i.e. heritability, repeatability and different types of correlation, maximum heritability was 0.25 plus minus 0.14 for birth weight. While minimum h eritability was observed for weight at nine months of age that was 0.11 plus minus 0.12 which indicates that all the growth traits were moderate to highly heritable suggesting that selection will be a best criteria for improvement of such traits in Nili-Ravi heifers. Maximum repeatability was 0.49 plus minus 0.05 for yearling weight while minimum repeatability was 0.25 plus minus 0.09 for birth weight. It shows that growth traits in Nili-Ravi heifers were moderate to highly repeatable. Among phenotypic correlations maximum correlation was 0.90 that was between weaning weight and weight at six months of age whereas minimum correlation was observed in birth weight and weight at three years of age that was 0.29. Maximum genetic correlation among, growth traits was observed in birth weight and yearling weight that was 1.11 while minimum figure 0.25 was obtained for correlation between yearling weight and weight at three years of age. In general environmental, phenotypic and gene t ic correlations were fairly large and positive indicating that selection for the improvement of one trait will positively affect the other trait.