Effect of reproductive rhythm and litter weaning age on the performance and body energy balance of rabbit does

One hundred twenty multiparous does were used. The does were synchronized to have parturition the same day (initial kindling). The trial lasted until the successive (final) kindling. At initial kindling, 22 does were selected for initial comparative slaughter. The remaining does were assigned to three reproductive rhythms, being mated 2 days postpartum (R2), 11 d pp (R11) or 26 d pp (R26). Within each rhythm, the does were further divided into two groups, whose litters were weaned at 21 (S21) or 25 (S25) d of age. A total of fifty-four does were pregnant and were slaughtered soon after the final kindling. Effect of reproductive rhythm. When increasing the kindling to mating interval, total milk production increased (5590 to 6065 g for R2 and R26 rhythms; P=0.05). Voluntary feed intake was not affected during lactation (364 g/d on average), but decreased during the dry period (182 to 169 g/d; P=0.05) and throughout the entire experiment (299 to 249 g/d; P<0.01) according to reproductive rhythm. At the final kindling, the number of kits born per litter was lower in does submitted to R11 rhythm (P<0.01). When increasing the kindling to mating interval, doe body water concentration decreased, while fat and energy increased (P<0.001) and a higher EB gain was recorded (from -123 to -4 to 97 g, P<0.001). As a consequence, body protein, fat and energy balances moved from negative values to equilibrium as reproductive rhythm became extensive (energy balance: -14.4%, -1.8% and +0.5% of the initial body content in R2, R11 and R26 does, respectively; P<0.001). Blood leptin concentration at 28 d after kindling was higher in R26 does (P<0.01), indicating higher body fat recovery due to lack of pregnancy. Effect of weaning age. Daily feed intake during the entire experiment was significantly lower in W21 does due to the longer dry period. At the final kindling, increasing weaning age from 21 to 25 d, both the number of kits born alive per litter (from 7.3 to 9.8; P=0.02) and doe body water concentration increased, while body fat and energy decreased (P<0.05). Therefore, W21 does showed an energy balance near equilibrium (-2.6%) while W25 does had negative fat (-14.1%) and energy (-7.9%) balances (P=0.08). Lower blood leptin concentration was recorded in W21 than W25 does (1.87 vs. 2.76 ng/ml, P=0.03).