Effects of increasing choice white grease in corn- and sorghum-based diets on growth performance, carcass characteristics, and fat quality characteristics of finishing pigs

A total of 120 pigs (60 barrows and 60 gilts; TR4 x PIC 1050; 54.4 kg initial BW) were used in an 83- d study to evaluate the effects of added fat in corn- and sorghum- based diets on growth performance, carcass characteristics, and carcass fat quality. Treatments were arranged in a 2 x 3 factorial with grain source (corn or sorghum) and added fat (0, 2.5, or 5% choice white grease; CWG) as factors. There were 2 pigs (1 barrow and 1 gilt) per pen and 10 replicate pens per treatment. Pigs and feeders were weighed on d 14, 22, 39, 53, 67, and 83 to calculate ADG, ADFI, and G: F. At the end of the trial, pigs were slaughtered and jowl fat and backfat samples were collected and analyzed for fatty acid profile. No interactions were observed for growth performance. Pigs fed sorghum- based diets had greater (P < 0.01) ADG than pigs fed cornbased diets. Adding CWG improved (linear, P < 0.01) ADG. Pigs fed corn- based diets tended to have greater (P < 0.09) carcass yield, 10th- rib backfat, and percentage lean than pigs fed sorghum- based diets. Add- ing CWG increased (linear, P = 0.02) 10th- rib backfat, tended to increase (linear, P = 0.08) HCW, and tended to decrease (linear, P = 0.07) percentage lean. There was no grain source x fat level interaction for iodine value (IV) in backfat, but an interaction (P = 0.03) was observed for IV in jowl fat. Adding CWG increased (P < 0.01) IV in jowl fat for pigs fed sorghum- and cornbased diets; however, the greatest increase was between 0 and 2.5% CWG in sorghum- based diets and between 2.5 and 5% CWG in corn- based diets. Pigs fed cornbased diets had less (P = 0.01) C18: 1 cis-9 and MUFA but greater (P = 0.01) C18: 2n-6, PUFA, and backfat IV than pigs fed sorghum- based diets. Increasing CWG in the diet increased (linear, P = 0.01) backfat IV. Of the 2 fat depots, backfat generally had a reduced IV than jowl fat. In summary, feeding sorghum- based diets reduced carcass fat IV and unsaturated fats compared with corn- based diets. As expected, adding CWG increased carcass fat IV regardless of the cereal grain in the diet.