GENETIC EVALUATION OF THE PERFORMANCE OF SOVIET CHINCHILLA AND CALIFORNIAN WHITE RABBITS
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Date
2003-08
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT :
The present study was conducted on 171 Soviet Chinchilla (SC) and 122 Californian White (CW) bunnies born during the years 1996 to 2001 in the Rabbit Production for Meat Scheme of the Department of Animal Genetics and Breeding, College of Veterinary Science, Rajendranagar, Hyderabad. The influence of season of birth, year of birth, litter size at birth and sex of bunny on various traits from birth to 16 weeks of age was studied by the least squares analysis. Step-down multiple regression equations were developed to predict the body weights based on biometrical measurements. The heritabilities and genetic and phenotypic correlations were estimated by half-sib correlation method based on the adjusted data. Season of birth had significant effect on pre-weaning litter weights of SC bunnies, while year of birth had no significant influence on litter weights of SC and CW breeds. Litter size at birth significantly influenced the litter weights. The pre-weaning body weights of SC bunnies at birth and 1week of age were significantly influenced by the season of birth, while the body weight of SC bunnies at one week and CW bunnies at 4 weeks of age were affected significantly by the year of birth. Litter size at birth exerted significant influence on the birth and weaning weights of SC and one and 2 week weights of CW bunnies. The post weaning body weights (5 to 16 weeks of age) of SC rabbits were affected significantly by the season of birth at 14 weeks of age, the year of birth at 6 weeks of age and the sex of bunny at 10 and 16 weeks of age but the influence of these effects were not significant in CW rabbits. The pre-weaning Average Daily Gain (ADG) and Cumulative ADG (CADG) of SC and CW bunnies were unaffected by the season of birth but the ADG during 3 weeks of age and CADG up to 3 and up to 4 weeks of age were affected significantly by the year of birth. Litter size at birth influenced the ADG and CADG of SC and CW bunnies significantly.
The post weaning ADG at 7 and 8 weeks of age in SC was affected significantly by the season of birth and the ADG during 5 and 6 and 9 and 10 weeks of age in SC and during 5 and 6 and 11 and 12 weeks of age in CW rabbits were significantly influenced by the year of birth. Sex of bunny had no significant effect on post weaning ADG in the two breeds studied.
The variations in the carcass traits between the various seasons and years of birth were insignificant in SC and CW breeds, except the significant effect of year of birth on edible offals weight in SC rabbits. Sex of bunny did not exert any significant influence on carcass traits of SC but this effect was significant on the weights of hot carcass, head, pelt mid-cut and hind cut of hot carcass in CW rabbits. The season and year of birth exhibited significant influence on biometrical measurements at various post weaning ages in SC and CW rabbits and with an exception on the chest girth at 6 weeks age in CW rabbits, sex of bunny had no significant influence on various body measurements of SC and CW rabbits. The R2-values of the step-down multiple regression equations for predicting the body weights based on biometrical measurements were low, indicating the low reliability of utilization of body measurements as indicators of the body weights. The heritability estimates of pre-weaning body weights, ADGs and CADGs ranged from low (up to 0.30) to medium (0.31 to 0.60) in SC and varied from low to high (more than 0.60) in CW bunnies and the genetic and phenotypic correlations varied from low to high in magnitude. The post weaning body weights and ADGs had heritabilities ranging from low to high in SC and from low to medium in CW and the corresponding genetic and phenotypic correlations were positive and ranged from low to high in SC rabbits. The carcass traits had heritabilities ranging from low to high in magnitude in SC and CW breeds. The genetic and phenotypic associations between various carcass traits varied from low to high in magnitude.
The biometrical measurements had heritabilities ranging from low (0.13 for ear length at 8 weeks age in SC and 0.01 for paunch girth at 12 weeks age in CW) to high (0.92 for height at 12 weeks age in SC and 0.80 for height at 16 weeks age in CW). The genetic and phenotypic correlations among the biometrical measurements and between the body weights and biometrical measurements were, in general, positive and ranged from low to high.
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