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Residual feed intake (RFI), defined as the difference between observed feed intake and that predicted from production and maintenance requirements, is one source of feed intake variability. The objective of our study was to evaluate RFI as a criterion of selection to improve feed conversion ratio (FCR). Data were collected in the frame of the French pig breeding scheme for four pig breeds in collective selection schemes between 2000 and 2009. This data set was used (1) to estimate genetic parameters for RFI, for production traits measured in station and in farm and for the estimation of excretion of nitrogen and phosphorus during growth, (2) to evaluate the response to selection of all of these traits using the OPTIPIG software and (3) to test scenarios using RFI as a selection criterion.
RFI showed moderate heritability for all the breeds (h² from 0.22 ± 0.03 to 0.33 ± 0.05). It is favorably correlated at the genetic level with FCR, with excretion, unfavorably with meat quality traits and is not well correlated with carcass composition and growth rate. Response to selection with indices currently used showed an increase of RFI in maternal breeds and a moderate diminution in paternal breeds. Excreted nitrogen will decease with different intensity according to the breed.
Thus, a selection index including RFI can be used for FCR improvement. For example, we show that a new index including RFI can be formulated to obtain similar responses to selection on the objectives as the current indices.
R. Saintilan, I. Merour, T. Tribout, J. Bidanel, L. Brossard, J. Van Milgen, H. Gilbert. Sélection pour l'efficacité alimentaire chez le porc en croissance : opportunités et conséquences de l'utilisation de la consommation moyenne journalière résiduelle dans les populations en sélection collective. 2012. Journées Recherche Porcine, 44, 13-18.