Abstract
Residual feed intake (RFI) gained attention as a potential alternative to the feed conversion ratio (FCR). Thus, this study aimed to estimate genetic parameters for different feed efficiency (FE) traits (FCR, RFI1 to RFI5) and their genetic correlation to on-test daily weight gain (ADG), backfat (BFT), loin muscle area (LMA), lean percentage (LP), and total feed intake (FI) for 603 Male Duroc (DD), 295 Landrace (LL), and 341 Yorkshire (YY). The common spatial pen effect was also estimated in these traits. Five RFI measures were estimated by regressing daily feed intake on initial testing age (ITA), initial testing weight (IBW), and ADG for RFI1; other models were the same as RFI1 except for additional BFT for RFI2; LMA for RFI3; BFT and LMA for RFI4; BFT, LMA, and average metabolic body weight (AMBW) instead of IBW for RFI5. Genetic parameters estimated using two animal models and the REML method showed moderate heritability for FCR in all breeds (0.22 and 0.28 for DD, 0.31 and 0.39 for LL, 0.17 and 0.22 for YY), low heritability for the majority of RFI measures in DD (0.15 to 0.23) and YY (0.14 to 0.20) and moderate heritability for all RFI measures in LL (0.31 to 0.34). Pen variance explained 7% to 22% for FE and 0% to 9% for production traits’ phenotypic variance. The genetic correlation revealed that selection against less complex RFI1 in DD and LL and RFI2 in YY would bring the most advantageous reduction to FI (0.71 for DD, 0.49 for LL, 0.43 YY) without affecting ADG in all breeds (0.06 for DD, −0.11 for LL, 0.05 for YY), decrease in BFT, and increase in LP in DD (0.51 in BFT, −0.77 in LP) and LL (0.45 in BFT, −0.83 in LP). Therefore, inclusion of these breed-specific RFI measures in the future selection criteria would help improve feed efficiency in the swine industry.
Highlights
In the modern capital-intensive pork production system, the feed accounts for about60% to 70% of the total cost of production [1]
The contemporary group accounts for differences in the environmental and managerial aspect for each testing batch and testing farm-batch; fixed covariates such as ITA and initial body weight (IBW) account for differences in the initial testing age and weight among animals, respectively; average daily gain (ADG) represents the growth performance of pigs during the testing period; BFT, loin muscle area (LMA), and lean percentage (LP) represent carcass components; and average metabolic body weight (AMBW) represents the maintenance requirements of each pig
Carcass components, and maintenance requirement traits included in the residual feed intake (RFI) models used in this study, only ADG, BFT, and AMBW were found significant, while LMA was not significant but remains worthy to be included in the model to determine its impact in the prediction accuracy
Summary
In the modern capital-intensive pork production system, the feed accounts for about60% to 70% of the total cost of production [1]. Azarpajouh et al [2] stated that improving FE could support industry competitiveness and reduce demand to global feed resources, which complement environmental sustainability. In the livestock and poultry industry, the FE is commonly measured through the feed conversion ratio (FCR) and gain to feed ratio (G:F), but less commonly measured using residual feed intake (RFI). The FCR and G:F ratio is obtained using two-component traits, the feed intake and weight gain, while RFI is measured by subtracting actual daily feed intake (DFI) and predicted daily feed intake (pDFI). The pDFI can be obtained by regressing DFI to different production traits, carcass components, and maintenance requirements of the animal.
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