Use of group records of feed intake to select for feed efficiency in rabbit

Models for genetic evaluation of feed efficiency ( FE ) for animals housed in groups when they are either fed ad libitum ( F ) or on restricted ( R ) feeding were implemented. Definitions of FE on F included group records of feed intake ( FI ¯ F ) and individual records of growth rate ( G F ) and metabolic weight ( M F ). Growth rate ( G R ) as FE measurement on R was used. Data corresponded to 5,336 kits from a rabbit sire line, from 1,255 litters in 14 batches and 667 cages. A five‐trait mixed model (also with metabolic weight on R, M R ) was implemented including, for each trait, the systematic effects of batch, body weight at weaning, parity order and litter size; and the random effects of litter, additive genetic and individual. A Bayesian analysis was performed. Conditional traits such asFI ¯ F | M F , G F andG F | M F , FI ¯ Fwere obtained from elements of additive genetics (FI ¯ F | M F , G F g andG F | M F , FI ¯ F g ) or phenotypic (FI ¯ F | M F , G F p andG F | M F , FI ¯ F p ) (co)variance matrices. In the first case, heritabilities were low (0.07 and 0.06 forFI ¯ F | M F , G F g andG F | M F , FI ¯ F g , respectively) but null genetic correlation between the conditional and conditioning traits is guaranteed. In the second case, heritabilities were higher (0.22 and 0.16 forFI ¯ F | M F , G F p andG F | M F , FI ¯ F p , respectively) but the genetic correlation betweenFI ¯ F | M F , G F p and G F was moderate (0.58). Heritability of G R was low (0.08). This trait was negatively correlated withG F | M F , FI ¯ F p andG F | M F , FI ¯ F g of animals on F, which indicate a different genetic background. The correlation between G R and G F was also low to moderate (0.48) and the additive variance of G F was almost four times that of G R , suggesting the presence of a substantial genotype by feeding regimen interaction.