Genetic parameters for production traits and measures of residual feed intake in large white swine

The purpose of this study was to estimate genetic parameters for ADG, backf at thickness and loin eye area (LEA), and measures of feed intake and effic iency for purebred Large White boars born from 1990 to 1997. Boars from 60% of the litters were culled at weaning based on a maternal breeding value t inder) of the dam, and remaining boars tn 26,706) were grown to 100 d of ag e. Selection of boars for individual pen testing was based on a combination of growth and maternal indices. Boars were fed a corn-soybean meal diet th at was 1.14% lysine, 19% protein, and 3,344 kcal/kg ME for approximately 77 d. Boars were weighed at the beginning and end of the test, and feed intak e was recorded. Daily feed intake (DFI), ADG, and feed:gain ratio (FG) were computed. Four measures of residual feed intake (RFI) were estimated as th e difference between actual feed intake and that predicted from models that included 1) initial test age and weight and test ADG (RFI1); 2) initial te st age and weight, test ADG, and backfat (RFI2); 3) initial test age and we ight, test ADG, and LEA (RFI3); and 4) initial test age and weight, test AD G, backfat, and LEA (RFI4). Genetic parameters were estimated using an anim al model and single- or multiple-trait DFREML procedures. Models included f ired effects of contemporary groups and initial test age as a covariate and random animal and litter effects. Heritability estimates for test ADG, DFI , FG, backfat, LEA, RFI1, RFI2, RFI3, and RFI4 were .24, .23, .16, .36,.24, .17, .11, .15, and .10, respectively. Genetic correlations between ADG and backfat, ADG and LEA, ADG and DFI, and ADG and FG were .37, .36, .82, and -.32, respectively. Genetic correlations between ADG and measures of residu al feed intake ranged from .11 to .18. Genetic correlations of backfat with LEA, DFI, and FG were -.27, .64, and .40, respectively. Genetic correlatio ns of backfat with RFI measures were higher when backfat was not included i n the estimation of RFI. Genetic correlations for LEA with DFI and FG were 0 and -.52, respectively. Genetic correlations for LEA with RFI measures we re all negative and ranged from -.31 to -.51. Genetic correlations indicate that selection for reduced RFI could be made without adversely affecting A DG. Backfat should also decrease,and LEA should increase. The amount of cha nge in backfat or LEA would depend on the measure of RFI used.