Body weight and its association with age at first calving and milk production in crossbred cattle of Kerala

Abstract

The present study was undertaken with a VIew of estimating body weights of crossbred calves in the field conditions of Kerala at birth, three, six and twelve months of age and to find association of these body weights with age at first calving and first lactation milk yield. The data for the present study were taken from the records of ICAR Field Progeny Testing Scheme of Centre for Advanced Studies in Animal Genetics and Breeding, Kerala Agricultural University. The data were of the 1993-2000 period. Body weights at birth, 3, 6, 12 months and at calving were predicted from body measurements using Minnesota formula given by J ohnson,( 1940). The data were analyzed using least squares analysis of variance to study the effects of non-genetic factors on different traits under study. The data adjusted for significant non-genetic factors .. were used to study the effect of sire and for estimating heritability and correlation among body weights and between body weights and

age at first calving and between body weights and first lactation milk yield. The overall average body weights of crossbred calves at birth, 3,6 and 12 months of age were 26.0 ± 0.38 kg, 48.7 ± 1.26 kg, 74.1 ± 2.81 kg and 151.0 ± 7.74 kg, respectively. Least squares analysis of variance has shown that the effect of season of birth was significant (P~0.05) only on body weight at six months of age. The influence of period of birth was significant for all body weights upto one year age except for body weight at six months of age. Centre was a significant source of variation for all body weights upto one year age, The mean Age at First Insemination, Age at first calving and Weight at first calving of crossbred cattle were 689.3 ± 22.9 days, 1013.6 ± 21.74 days and 284.9 ± 7.71 kg respectively. The season of birth did not affect age at first insemination, age at first calving and weight at first calving. The significant (P~0.05) influence of period of birth and centre were 11

observed on age at first insemination and age at first calving only but not on weight at first calving. The effect of period of calving and centre on first lactation milk yield was significant whereas the effect of season of calving and age at first calving did not affect first lactation milk yield. The average first lactation milk yield of crossbred cows was 1958.5 ± 30.74 litres. The sire wise means of body weight at six months of age, weight at first calving and first lactation milk yield did not differ significantly but sire effect was significant (P~0.05) in all the other traits. Heritability estimates were calculated by paternal half sib method for different traits under study. The low heritability estimate was obtained for birth weight, body weight at six months of age, age at first calving and weight at first calving. But the heritability estimates of body weight at three months of age and body weight at twelve months of age were high. Age at first insemination was moderately heritable. The heritability estimate of first lactation milk yield was -0.069 ± 0.05. iii

Association among body weights and that between body weights and age at first calving followed no definite trend. However, the genetic correlation (0.46) between body weight at six months and first lactation milk yield and high, positive (> 1) genetic correlation between body weight at twelve months and first lactation milk yield indicates strong genetic association of body weight at six months and body weight at twelve months with first lactation milk yield and their relationship can be used advantageously for selection of heifers for milk production under field conditions