Selection response and genetic parameters for residual feed intake in Yorkshire swine1

Abstract

Residual feed intake (RFI) is a measure of feed efficiency defined as the difference between the observed feed intake and that predicted from the average requirements for growth and maintenance. The objective of this study was to evaluate the response in a selection experiment consisting of a line selected for low RFI and a random control line and to estimate the genetic parameters for RFI and related production and carcass traits. Beginning with random allocation of purebred Yorkshire littermates, in each generation, electronically measured ADFI, ADG, and ultrasound backfat (BF) were evaluated during a approximately 40- to approximately 115-kg of BW test period on approximately 90 boars from first parity and approximately 90 gilts from second parity sows of the low RFI line. After evaluation of first parity boars, approximately 12 boars and approximately 70 gilts from the low RFI line were selected to produce approximately 50 litters for the next generation. Approximately 30 control line litters were produced by random selection and mating. Selection was on EBV for RFI from an animal model analysis of ADFI, with on-test group and sex (fixed), pen within group and litter (random), and covariates for interactions of on- and off-test BW, on-test age, ADG, and BF with generations. The RFI explained 34% of phenotypic variation in ADFI. After 4 generations of selection, estimates of heritability for RFI, ADFI, ADG, feed efficiency (FE, which is the reciprocal of the feed conversion ratio and equals ADG/ ADFI), and ultrasound-predicted BF, LM area (LMA), and intramuscular fat (IMF) were 0.29, 0.51, 0.42, 0.17, 0.68, 0.57, and 0.28, respectively; predicted responses based on average EBV in the low RFI line were -114, -202, and -39 g/d for RFI (= 0.9 phenotypic SD), ADFI (0.9 SD), and ADG (0.4 SD), respectively, and 1.56% for FE (0.5 SD), -0.37 mm for BF (0.1 SD), 0.35 cm(2) for LMA (0.1 SD), and -0.10% for IMF (0.3 SD). Direct phenotypic comparison of the low RFI and control lines based on 92 low RFI and 76 control gilts from the second parity of generation 4 showed that selection had significantly decreased RFI by 96 g/d (P = 0.002) and ADFI by 165 g/d (P < 0.0001). The low RFI line also had 33 g/d lower ADG (P = 0.022), 1.36% greater FE (P = 0.09), and 1.99 mm less BF (P = 0.013). There was not a significant difference in LMA and other carcass traits, including subjective marbling score, despite a large observed difference in ultrasound-predicted IMF (-1.05% with P < 0.0001). In conclusion, RFI is a heritable trait, and selection for low RFI has significantly decreased the feed required for a given rate of growth and backfat.

Liver and skeletal muscle mitochondria proteomes are altered in pigs divergently selected for residual feed intake1,2

“…We have reported the unique protein profile and PTM differences in comparisons of pigs that were genetically and phenotypically divergent in feed efficiency during the growing period. The differences in growth performance reported in these comparisons are consistent with previously published results from these same lines of pigs (Cai et al, 2008;Grubbs et al, 2013b;Harris et al, 2012;Smith et al, 2011) and another similar swine RFI genetic selection project (Barea et al, 2010;Lefaucheur et al, 2011). Phenotypic differences in RFI without genetic selection for RFI have also been reported in cattle Table 5.…”

“…Nine gilts from the high RFI and 9 gilts from the low RFI lines of the eighth generation of the Iowa State University swine RFI selection project were used in this experiment (Cai et al, 2008). Pigs were selected by matching weights across lines and individually penned with ad libitum access to water and feed.…”

“…Growth performance is reported in Table 1. Residual feed intake phenotype was calculated as previously described (Cai et al, 2008;Young et al, 2011).…”

“…To elucidate some of these biological differences in feed efficiency, we used Yorkshire pigs that have been divergently selected for residual feed intake (RFI; Cai et al, 2008). Residual feed intake is a measure of feed efficiency calculated by determining the difference between an individual animal's observed feed intake and its expected feed intake based on the animal's rate of growth and backfat Cai et al, 2008). Pigs with a low RFI consume less feed than expected while maintaining similar growth performance and back fat compared to high RFI pigs (Barea et al, 2010;Boddicker et al, 2011).…”

Phenotypic and genetic relationships between growth and feed intake curves and feed efficiency and amino acid requirements in the growing pig

“…phenotypic correlation (0.74 ± 0.01) and genetic correlation (0.52 ± 0.05) estimated between FCR and RFI in a previous study of the same Large White maternal population (Saintilan et al, 2013). Comparing average trait values between the feed efficiency groups also illustrated correlation estimates previously reported with RFI and FCR on similar (Gilbert et al, 2007;Cai et al, 2008) or different (Clutter, 2011;Saintilan et al, 2013) breeds. Because of its calculation, RFI is phenotypically independent from ADG, LMC, BFT and DP, and the corresponding genetic correlations are expected to be low.…”