Genetics analysis of body weight and litter traits of pure bred rabbits

Abstract

The experiment was carried out at the Rabbit Research Station attached to the Centre for Advanced Studies in Animal Genetics and Breeding, Mannuthy. Rabbits belonging to three pure breeds viz. Grey Giant, Soviet Chinchilla and New Zealand White formed the materials for the study. From each breed, seven males were taken and each male was mated to two females each and in all 14 females and seven males were considered in each breed. Seven parameters of reproductive efficiency of the dam were taken and body weights of rabbits born were recorded at four, six, eight, ten and twelve weeks of age. The mean values of body weight at four, six, eight, ten and 12 weeks were highest in Soviet Chinchilla rabbits compared to Grey Giant and New Zealand white, which had the lowest weights among the three breeds. Breed effect was significant for the body weight in all the weeks. The effect of sex on the body weight of rabbit was non – significant in all the three breeds. The sire of the offspring affected the body weight at each stage in all the three breeds. There was also a dam effect on body weight. In general the estimates of heritability were high in all the three breeds. The estimates of heritabilities for body weight show some marked effects of age. In particular, the pre – weaning weights had a high or moderate value compared with the lower estimates obtained for post – weaning weights. Estimates of heritability from the dam component revealed generally larger heritabilities than those of sire component except in New Zealand White rabbits. The phenotypic correlations between the body weights at different ages were positive and generally high, and tended to decrease in value as the differences between the two ages increased. The genetic correlations between body weights for the three breeds showed that all of these relationships were positive, like the corresponding phenotypic estimates. The environmental correlations were generally very high in all the three breeds except in Grey Giant rabbits when estimated based on (Sire + dam) method which may be due to sampling error. It was found that the effect of the breed on the gestation length was non – significant. The breed of the rabbit significantly affected the litter size at birth. Soviet Chinchilla breeds had the lowest litter size at birth. The effect of breed was gain highly significant for the litter size at weaning. Soviet chinchilla rabbits had the lowest litter size at weaning also. Maximum pre – weaning mortality was seen in the Soviet Chinchilla breed though the effect of the breed was found to be non – significant. The highest litter weight at weaning was seen in grey Giant rabbits and the lowest in the New Zealand White rabbits though the number of rabbits alive in New Zealand White breed were more than in the Soviet Chinchilla rabbits. The mean litter weight at weaning was highest in Soviet Chinchilla rabbits. The overall sex ratio was 52 percent. The estimates of heritability for the litter size at birth and at weaning were negative and hence adjusted to zero.