Using collective feed intake data to select for feed efficiency on full or restricted feeding regimen

Variance components of average daily gain (ADG) on both full and restricted feeding regimen (FF and RF), and average daily feed intake (ADFI) on FF of kits raised in collective cages were estimated for each week of the fattening period by using a multiple-trait model analysis. Data from a total of 6,264 kits from 1,317 litters housed in 812 cages along 14 batches were used for the analysis. Results indicate that weighted estimate of heritability for ADG was 0.47 (0.03) and 0.40 (0.03) on FF and RF, respectively, but genetic variance was much smaller on RF. The interaction between the genotype and feeding regimen was 13% of the mean phenotypic variance of both traits. Heritability of ADFIFF was 0.28 (0.06). Breeding values of ADGRF conditional on ADGFF represents the effects of genes only involved in feed efficiency. The heritably of this trait is equal to that for ADFIFF conditional on ADGFF (a different measurement of feed efficiency) but its genetic variation is lower. The genetic correlation between them was nearly null which indicates that these traits are related to different components of feed efficiency.

Key words: Feed efficiency, feeding regimen, GxE interaction, genetic parameters, collective data