Microrabbits: a factorial design to evaluate genetic and maternal effects on growth and feed efficiency in a line selected for residual feed intake

The aim of this study was to evaluate the significance of neonatal environment (ultimately including the microbiota composition) on feed efficiency. For that purpose, half of the rabbits of the G10 line, selected for 10 generations on residual feed intake (RFI), were fostered by does of a non-selected control line G0, and vice versa. In parallel, collaterals were adopted by mothers from their original line. Around 900 animals were produced in 3 successive batches and raised in individual or collective cages. Traits analyzed in this preliminary study were weights at weaning (32 days) and at the end of the test (63 days), average daily gain (ADG), feed intake between weaning and 63 days (FI), feed conversion ratio (FCR) and RFI. Line of the rabbit, type of housing (collective or individual cages: 2 levels) and batch (3 successive mating:3 levels) were significant effects for all traits. G10 does had a negative effect on FCR (+0.06, P = 0.04), irrespective of the line of young rabbits. G10 animals were lighter than G0 at 32 days (-83 g) and at 63 days (-161 g). They also had a lower ADG (-2.36 g/day), FCR (-0.36), RFI (-548 g/day) and a lower FI (-839 g), confirming a better feed efficiency. Our results demonstrate that selection on feed efficiency was successful for direct effect but maternal effects were degraded by the selection. This study is part of the Feed-a-Gene Project, funded from the European Union’s H2020 Programme under grant agreement no 633531.