Effects of adding minimally refined cottonseed oil or crude glycerol to diets containing 40% corn distiller's dried grains with solubles on growth performance, carcass characteristics, and pork fat firmness of growing-finishing pigs.

Abstract

Diets containing more than 20% distiller's dried grains with solubles (DDGS) reduce fat firmness in pork, but supplementation of cottonseed oil or crude glycerol may improve fat firmness. The objective of this study was to assess the effect of feeding minimally refined cottonseed oil or crude glycerol on growth performance, carcass composition, and fat quality of growing-finishing pigs. Mixed sex pigs ( = 216; 24 ± 4 kg initial BW) were blocked by BW and allotted to 1 of 3 dietary treatments: 1) a basal corn-soybean meal diet with 40% DDGS (CON), 2) CON diet plus 5% minimally refined cottonseed oil added throughout the experiment (COT), or 3) CON fed during the first 8 wk and CON + 8% crude glycerol fed during the last 6 wk of the experiment (GLY). Although diets were not isocaloric, total AA-to-ME ratios were calculated to be equal among diets. Carcass composition was estimated using real-time ultrasound 2 d before harvest. Gilts (16/treatment) closest to the mean BW of each pen were harvested (115 ± 8 kg BW), and bellies were retrieved for in-depth analysis of fat quality. Belly fat was sampled and analyzed for fatty acid composition. Overall, ADFI of pigs fed COT (2.30 kg/d) was less ( < 0.01) than that of pigs fed CON or GLY (2.47 and 2.49 kg/d, respectively). Pigs fed COT (0.93 kg/d) had greater ( < 0.01) ADG compared with pigs fed CON or GLY (0.88 and 0.87 kg/d, respectively). Greater ( < 0.01) G:F was observed for pigs fed COT (0.41) than for pigs fed CON or GLY diets (0.36 and 0.35, respectively). Final BW of pigs fed COT (124.3 kg) was greater ( < 0.01) than that of pigs fed CON or GLY (118.9 and 118.6 kg, respectively). Pigs fed COT had greater ( < 0.01) HCW (94.9 kg) compared with pigs fed CON or GLY (89.9 and 89.2 kg, respectively). No differences were observed for dressing percentage (75.7, 76.3, and 75.3%), fat-free carcass lean percentage (50.5, 49.7, and 50.0%), and belly flop angle (6.21, 8.57, and 6.06°) for CON, COT, and GLY, respectively. Pigs assigned to COT had higher ( < 0.01) melting point of belly fat compared with pigs assigned to CON or GLY (30.4 vs. 26.3 and 25.3°C, respectively). Pigs fed COT had increased ( < 0.05) SFA, PUFA, and iodine value (IV) compared with CON-fed pigs. Glycerol supplementation had no influence on SFA, MUFA, and PUFA concentrations or IV of belly, jowl, and back fat compared with CON. In conclusion, COT diets improved growth performance due to greater energy density, but carcass composition was not affected by treatments. In this experiment, feeding neither COT nor GLY improved fat firmness of pigs fed diets containing 40% DDGS.