Genetic and Phenotypic Parameters of Rabbit Individual Body Weight in the Preweaning Period

The preweaning weight of kits has been related to their mortality during the suckling period. Selecting rabbit kits for individual body weight in the first days of life could be interesting; however, better knowledge of body weight's heritability during the preweaning period is necessary to determine the opportune moment for selection. A total of 1696 growth records of kits from 81 females of the ITLEV2006 synthetic line were analysed in order to estimate the genetic and non-genetic parameters for individual body weight at birth as well as at 5, 7, 14, 21, 28, and 35 days of age. The estimates of heritability (h2) for individual weight were between low (0.11 at birth, 0.16 at 5 days, and 0.17 at 7 days) and moderate (0.21, 0.21, 0.24, and 0.21 at 14, 21, 28, and 35 days, respectively). Weight at birth showed a strong and positive genetic correlation with weight at 5 days (+0.79) and 7 days of age (+0.78), but the correlation was low for the rest of the weight measurements (+0.41, +0.49, +0.54, and +0.54 with weight at 14, 21, 28, and 35 days, respectively). Weight at 5 days and 7 days displayed strong and positive genetic correlations with the rest of the weight measurements (higher than +0.83). The values of the common litter effect (c2) were high, and they increased with age from 0.43 at birth to 0.66 at 35 days of age. The values of the maternal permanent effect (p2) were low compared to those of the common litter effect (c2), varying between 0.04 and 0.11. In conclusion, opting to select for body weight at 5 or 7 days of age would yield a greater response compared to selecting for birth weight. This approach would indirectly increase the kits' weight at birth and at weaning, thereby reducing preweaning losses.

Genetic studies on growth and production traits in German Angora Rabbits under sub-temperate climatic conditions

This study aimed to assess the effect of genetic and non-genetic factors on growth, wool yield and wool characteristics of German Angora rabbit. Data was collected on 607 adult rabbits over a period of four years (2018-2021). The least squares means of body weights (g) at various ages, wool yield (g) at I, II, III and IV clip and wool characteristics assessed by staple length (cm) and fiber diameter (μ) were estimated. Sires of the rabbit progenies demonstrated highly significant effect (P<0.01) on the studied traits except wool characteristics. Sex of the rabbits had significant effect on body weight at 10th, 12th, 14th, 16th, 24th weeks of ages and wool yield at III clip, with greater estimates of females than the males for III clip, staple length, and 24th weeks body weight. Winter and autumn seasons were the most favourable seasons in comparison to summer season for estimated traits. Winter born kits had the highest body weights of 683±20.1, 961±24.3, 1263±27.5, 1484±34.0, 1735±37.1, 1942±40.1, 2136±36.9, 2232±36.7, 2341±37.4 and 2429±37.4 g and the summer born kits had the lowest body weights of 588±22.0, 820±27.2, 1037±31.2, 1307±38.0, 1515.79±41.0, 1696±44.1, 1847±41.4, 1920±41.0, 2034±42.4 and 2139±41.6 g, at biweekly interval from 6th to 24th, respectively. Rabbits with litter size less than six performed better in comparison to other groups for all growth traits and wool yield at I and III clip. The heritability estimates were found positive and high in magnitude for all growth traits, moderate for wool clip at different clips and very low for staple length. Genetic and phenotypic correlations were found to be very high and significant among growth traits and low to moderate among wool traits. The study revealed scope for further improvement in growth and wool yield by adopting selective breeding in the colony.