The effect of litter size on reproductive performance of rabbit does and kit mortality over the first two parities

Under field conditions, rabbit reproductive performance and kit survival are critical at the first parities, when females have not completed their morphological and physiological development. During the first breeding cycles, litter size is usually standardized at a maximum 8-9 kits to allow for a sufficient milk intake and reduce kit mortality. To improve the management and welfare of reproducing does, this study evaluated the effect of increasing litter size from 9 to 11 kits in rabbit does at their first two reproductive cycles. Ten days before kindling, 72 crossbred does (Hyplus Grimaud Frère) were allocated to six experimental groups resulting from the combination of 2 parity orders (1st vs. 2nd parity, P1 vs. P2) × 3 standardised litter sizes (9 vs. 10 vs. 11 kits). Immediately after kindling, litters were standardized and monitored until weaning (33 days of age). The P2 consistently outperformed P1 in kit birth weight (59.6 vs. 54.6 g; P<0.01), daily weight gain (24.6 vs. 21.1 g/d; P<0.001), and litter and doe feed intake (+24%; P<0.001). The P2 had also higher live weight at 19 (+4%; P<0.05) and 33 days (+7%; P<0.001) of lactation. Kit mortality at weaning was significantly higher in P1 than in P2 (20.5% vs. 10.1%; P<0.01). Increasing litter size reduced weaning kit weight (877 vs. 827 vs. 776 g in litters with 9, 10 and 11 kits, respectively; P<0.001), whereas doe live weight and body condition were not affected. Kit mortality increased from 11-12% in litters of 9 and 10 kits to 22.5% in litters of 11 kits (P<0.05), on average of the two parity orders. In conclusion, increasing the parity order improved litter performance and reduced kit mortality, whereas standardization to 11 kits increased mortality and lowered weaning weight, making it less advisable during the first reproductive cycle.