INFLUENCE OF THE NUMBER OF SUCKLING YOUNG AND THE FEED LEVEL ON FETAL SURVIVAL AND GROWTH IN RABBIT DOES

This study was undertaken to determine the influence of various degrees of nutritional deficit on foetal survival and growth in pregnant and lactating does. All females were mated within 12 h of parturition (d 0) and slaughtered at d 28. For around half of them, lactation was terminated at parturition and does were fed ad libitum throughout gestation (CNL group, n = 28) or feeding was restricted from d 15-28 (RNL group, n = 27). Other females were allowed to nurse 4 (FL group, n = 27) or 10 young (TL group, n = 27), and were fed ad libitum. Live-weight variation between d 14 and 28 (deltap1428) varied highly between groups (CNL: +194 g; RNL: +112 g; FL: -1 13 g; TL: -1 97 g; P < 0.01). Late foetal mortality (> d 15) was significantly increased in lactating groups (FL: 10.4%, TL: 15.5%) compared with non-lactating groups (CNL: 5.4%; RNL: 3.6%) without any influence of deltap1428. The weight of the foetuses was significantly lower in the lactating groups (CNL: 39.7 g; RNL: 39.3 g; FL: 37.5 g; TL: 34.9 g; P < 0.001) and was negatively related to deltap1428 (r = 0.47; P < 0.001). The concentrations of progesterone were lower in lactating than in non-lactating does (TL + FL vs CNL + RNL; P < 0.01) on d 7 and 17, but similar on d 28. These results suggest that the detrimental effect of lactation on foetal survival and growth can be decreased by reducing the number of suckling young.