REPEATABILITY ESTIMATES AND GENETIC EFFECT ON CARCASS AND GROWTH PARAMETERS OF SOME RABBIT BREEDS AT VARIOUS AGES

Abstract

A study was conducted using nine parent breeds of rabbits namely New Zealand White, Havana, Checkered Giant, locally adapted, Flemish Giant, Chinchilla, Rex, California White and Dutch. These breeds when randomly crossed severally produced 66 kits, which were grouped into 16 genotypes namely California white and California white (CF vs CF), Checkered giant and Checkered giant (CG vs CG), Chinchilla and Chinchilla (CH vs CH), Dutch and Dutch (DT vs DT), Flemish giant and Flemish giant (FG vs FG),Locally adapted and locally adapted (LA vsLA), New Zealand white and New Zealan d white (NZW vs NZW), Rex and Rex (Rx vs Rx), California and Dutch; Dutch and Locally adapted (CF x DT vs DT x LA), Flemish giant and Locally adapted; Flemish giant (FG XLA vs FG), Havana and Dutch; Locally adapted (HV x DT vs LA), Havana and Dutch; Flemish giant (HV x LA vs FG), New Zealand White and California White; California White (NZW x CF vs CF), New Zealand White and Dutch; New Zealand White (NZW x DT vs NZW), New Zealand White and Rex; Rex (NZW x Rx vs Rx), Rex and Dutch; Dutch and Locally adapted (Rx x DT vs DT x LA), Dutch, Rex, California White and Chinchilla. Data on body weaning weights linear body measurements and carcass parameters of these genotypes were collected for this study. The body weight and linear body measurements such as ear length (EL), trunk length (Trkl), chest girth (CG), height at withers (HW), body length (BL), nose to shoulder length (Nsl) and tail length (Tll) were taken at different ages. The experiment lasted for a period of nine (9) months. Results of the study showed that genotype was important source of variation for body weight, weaning weight and linear body measurements. Genotype had significant (P < 0.05) effect on all parameters. Crosses of New Zealand White (NZW vs NZW), Checkered giant (CG vs CG), New Zealand White and California White (NZW x CF vs CF), New Zealand White and Rex (NZW x Rx vs Rx), Flemish giant and locally adapted (FG x LA vs FG), performed well in all the linear body measurements, Crosses of New Zealand white and California (NZW x CF vs CF) had the highest weight at birth, 21and 28 days, Checkered giant (CG vs CG) had highest mean weaning weight at age 28 days. Sex effect of birth weight showed significant difference at day 21, but not in day 28. Notwithstanding, the males were observed to have the higher mean values at 21 and 28 days, except in day 21 where females had the higher mean values in body length and tail length. Kits of 2nd parity recorded the highest least squares means of body weight and linear body measurements compared to kits of parities 1 and 3. The highest and strongest correlation coefficient (r = 0.92) was recorded between trunk length and weaning weight; (r = 0.91) body length and trunk length. The result on the study of relationships between body weight and linear body traits of genotypes at 21 and 28 days using the simple linear and quadratic functions revealed a significant effect and strong interrelationship between them. Trunk length, chest girth and body length were best predictors of body weight. The regression analysis showed that the simple linear model gave the best prediction based on the coefficient of determination (R2) values. Trunk length and chest girth had the highest R2 of 99.995, meaning that the entire body dimensions were good indicator of live body traits. Repeatability allows for performance of individual to be accessed for future purpose. It remains a useful tool for predicting the performance as well as the selection of individuals. The results of this study showed that repeatability estimate was moderate, thereby making breeding of rabbit types of various genotypes at different agess feasible. Hence, among the genotypes, it was observed that crossbreeding of rabbits produced superior performance at various ages, because, they appeared to harness the additive genes from their different parents that might result in positive heterotic effects.