Reproductive rhythm and litter weaning age as they affect rabbit doe performance and body energy balance

Abstract

Abstract One hundred and twenty multiparous does were synchronized to give birth the same day (initial kindling). The trial lasted until the successive (final) kindling. Immediately following initial kindling, 22 does were selected for comparative slaughter. The remaining does were assigned to three reproductive rhythms and mated 2 (R2), 11 (R11) or 26 (R26) days post partum. Within each rhythm, the does were further divided into two groups with litters weaned at 21 (W21) or 25 (W25) days of age. A total of 54 does were pregnant and were slaughtered soon after final kindling. By increasing the kindling-to-mating interval from 2 to 26 days, total milk production was increased (5590 to 6065 g for R2 and R26, respectively;P< 0·05); voluntary food intake during lactation was not affected (356 g/day on average), but during the dry period was reduced (182 to 169 g/day;P< 0·05) in this way accounting for a decrease during the experimental period on the whole (299 to 249 g/day;P< 0·01). At the final kindling, the number of kits born per litter was lower in does submitted to the R11 than to the R26 rhythm (P< 0·01). By increasing the kindling-to-mating interval, doe body water concentration decreased, while fat and energy increased (P< 0·01) and higher empty body gain was recorded (from −123 to −4, and to +97 g, in R2, R11 and R26 does, respectively;P< 0·001). As a result, body protein, fat and energy balances changed from negative values to approach equilibrium as reproductive rhythm became extensive (energy balance: −0·14, −0·02 and +0·01 of the initial body content in R2, R11 and R26 does, respectively;P< 0·001). At 28 days after kindling, blood leptin concentration was higher (P< 0·01) and IGF-1 lower (P< 0·05) in R26 does. Daily food intake throughout the experiment was lower (P< 0·05) in W21 does due to the longer dry period. Increasing weaning age from 21 to 25 days increased both number of kits born alive per litter (from 7·4 to 9·6;P< 0·05) and doe body water concentration, while body energy tended to decrease (P< 0·1). At 28 days after kindling lower blood leptin concentration was recorded in W21 than W25 does (1·87 v. 2·76 μg/l,P< 0·05).