Document Type : Original Article
Author
Animal Production Research Institute, Agriculture Research Center, Ministry of Agriculture, Dokki, Cairo, Egypt.
Abstract
This study was carried out on 765 litters of New Zealand White(NZW)rabbit breed and extended for about 5years to study some factors affecting milk traits. The effect of season of kindling on milk production was higher significantly during most of the weeks of the study and total milk yield. The insignificant effect of parity on milk production and the milk yield during 1st, 3rd week and total milk yield but increased gradually with the advancement of parity from 1st to 3rd parity and decreased for other parities. Increasing the litter size from 3 to 9 was associated with a significant increase for milk production during 1st, 2nd, 3rd, 4th week and total milk yield. Teats number were significant in milk yield during most of weeks and total milk yield of the study. Genetic correlation between litter size at birth and litter weight were positive and high and ranging from 0.48 to 0.66.Genetic correlations between litter size at birth and litter weight at weaning were low while the phenotypic correlations were positive and high and ranging from 0.34 to 0.74.Selection indices for litter and milk traits were constructed incorporating litter size at birth (X1), litter size at weaning (X2), litter weight at birth (X3), litter weight at weaning (X4) and pre-weaning mortality (X5), milk yield during the 1st, 2nd, 3rd and 4th week (X1, X2, X3, X4)and total milk yield (X5) to improvement of productivity of does of New Zealand White rabbits. Relative efficiencies(RIH ) in litter traits were high for I1 (based on five traits) to other indices
Relative efficiency(RIH ) in milk traits were high for I2 (based on four traits) to other indices and recommended for use to maximize response and apply selection on this index. The expected genetic gain changes in litter size at birth was low in all of the indices used and ranging from -0.031 to 0.129 young, in litter size at weaning was low and ranging from 0.065 to 0.100 young, in litter weight at birth was moderate or high and ranging 3.71 to 9.34 g, in litter weight at weaning was high and ranging 108.99 to 131.65 g and in pre-weaning mortality was ranging 0.282 to 1.30 young. The expected genetic gain changes were high in milk yield during the 1st, 2nd, 3rd,4th week and total milk yield and ranging 14.39 to 34.77g, 42.33 to 54.26g, 83.71 to 105.66 g, 10.45 to 32.70 g and 143.60 to 151.76 g.
Conclusively, Milk production was higher in winter months than other seasons. For litter traits recommended for use to maximize response and apply selection on index I1 (based on five traits).For milk traits recommended for use to maximize response and apply selection on this index, I2 (based on four traits).
Keywords
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