Abstract Two experiments evaluated different fat sources and levels on growth performance and carcass characteristics in commercial finishing pigs. In Exp. 1, pigs (n = 2,160 337 × 1050, PIC; initial BW 37.3 ± 0.93 kg) were used. Pens of pigs were blocked by initial BW and randomly assigned to 1 of 4 dietary treatments. Three of the treatments included: 0, 1, and 3% choice white grease fed throughout the trial. The final treatment contained no added fat until pigs were approximately 100 kg, and then the diet containing 3% fat was fed. Experimental diets were fed over 4 phases and were corn-soybean meal-based with 40% dried distillers grains with solubles. There were 27 pigs per pen and 20 replications per treatment. Overall, increasing choice white grease decreased (linear, P = 0.006) ADFI and increased (linear, P = 0.006) G:F without influencing ADG (Table 1). Pigs fed 3% fat only during the late finishing phase (approximately 100 to 129 kg) had similar G:F compared with pigs fed 3% fat for the entire study. Increasing fat tended to increase (linear, P = 0.068) HCW. In Exp. 2, pigs (n = 2,011 PIC 1050 × DNA 600; initially 28.3 ± 0.53 kg) were used. Pens of pigs were blocked by location in the barn and randomly assigned to 1 of 5 dietary treatments arranged in a 2 × 2 + 1 factorial with main effects of fat source (choice white grease or corn oil) and level (1 or 3% of the diet) and a control diet with no added fat. There were 16 replications per treatment with 21 to 27 pigs per pen. Overall, increasing fat, regardless of source, increased (linear, P < 0.001) ADG, decreased (linear, P = 0.013) ADFI, and increased (linear, P < 0.001) G:F. Increasing fat increased (linear, P ≤ 0.016) HCW, carcass yield, and backfat depth (Table 2). There was a fat source × level interaction (P < 0.001) in belly fat iodine value (IV), where IV increased to a greater extent in pigs fed diets containing corn oil with only a small increase in IV in pigs fed diets with choice white grease. In conclusion, the results from these experiments suggest that increasing fat from 0 to 3%, regardless of source, produced variable responses in ADG but consistently improved G:F. Increasing fat increased HCW, carcass yield, and backfat depth, but feeding diets containing corn oil increased belly fat IV to a greater magnitude than choice white grease.
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