CHARACTERIZING LITTER LOSSES IN PUREBRED NEW ZEALAND WHITE RABBITS
M. Mohamed Abdelsabour Elmaghraby, S. Zakaria Elkholya
Eight hundred sixty six kits of 104 New Zealand White litters were studied for the rate of stillbirth, within litter mortality (M) between birth and day 21 of age (M0-21) where kits rely solely on milk, day 22 to weaning (M22-28) and postweaning to marketing (M29-70). Overall least squares means were 6.96% (stillbirth), 10.62% (M0-21), 0.55% (M22-28) and 3.08% (M29-70). In 30.77% of litters, all kits survived to marketing. Dead kits at birth and those died within the first week of age had significantly lower body weight (bwt) than their surviving littermates. M0-21 was higher in litters of low mean kit birth weight (≤ 60 vs > 60 g). Kit survival pre- (M0-21) and postweaning (M29-70) was better when their does gained > 250 g bwt during the first three weeks post-kindling compared to dams losing bwt or gaining < 250 g. The rate of stillbirth tended to increase (P = 0.06) with longer gestation periods. M0-21 was higher in large litters (alive kits ≥ 9 vs < 9 kits). Summer and spring born litters experienced significantly higher M0-21 than autumn and winter born ones. Stillbirth increased with parity (P< 0.05). Repeatability was 0.31 for M0-21 and low (0.00 to 0.07) for other traits. Conclusion: Small kit size, dam bwt loss or low bwt gain during the first three weeks postnatal, large litters, summer and spring kindlings, and 3rd or higher kindling orders reduce kit survival, particularly at birth and during the first three weeks of age.
Key words: Rabbits, litter mortality, environmental factors, repeatability