Influence of the breed and litter breed composition on the growth, survival, and health of rabbits

The aim of this work was to investigate the effect of the breed and the litter breed composition on the growth, survival, and health of rabbits. Two genetic types were compared: purebred INRA 1777 ( INRA ) and crossbreed ¾ Fauve-de-Bourgogne × ¼ INRA 1777 ( Crossbreed ). To study the effect of the litter breed composition, two cross-fostering strategies were used for suckled rabbits at birth: within-genetic type and between-genetic type, where the dam raised kits of the same or different genetic types. Litter composition was maintained after weaning. A total of 1 670 growing rabbits were monitored from birth to weaning (at 35 days of age), and then 1 030 rabbits were monitored from weaning to 64 days of age. Four cohorts were raised from September 2019 to April 2020. Health was evaluated using visual health scores and white blood cell counts. Crossbred rabbits had a higher survival rate in the preweaning period (+14.9% points; P < 0.001), and a higher percentage of healthy individuals at 64 days of age (+13.9% points; P < 0.001) than purebred rabbits, even though the survival rate was equivalent (92%) between the two genetic types in the postweaning period. Crossbred rabbits were lighter than INRA rabbits (−128 g at 64 days of age; P < 0.001). The between-genetic type cross-fostering strategy had a positive effect on survival in the preweaning period (+4.6% points for INRA and +13.3% points for Crossbreed; P < 0.001) compared to the within-genetic type cross-fostering strategy. No lasting effects of the litter breed composition on postweaning survival or health were observed. Mixing kits of different genetic types within litters may be a strategy to improve the overall herd health and help reduce the use of antibiotics in rabbit farming.