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* Department of Animal Science, University of Arkansas, Fayetteville, 72701
Darling International Inc., Irving, Texas 75038
Abstract
Crossbred pigs (n = 288) were used to test the interactive effects of dietary fat source and slaughter weight on live performance, carcass traits, and fatty acid composition of the LM. Pigs were blocked by initial BW, and, within each of 9 blocks, pens (8 pigs/pen) were randomly assigned to either control corn-soybean meal grower and finisher diets devoid of added fat (Ctrl) or diets formulated with 5% beef tallow (BT), poultry fat (PF), or soybean oil (SBO). Immediately after treatment allotment, as well as at mean block weights of 45.5, 68.1, 90.9, and 113.6 kg, 1 pig was randomly selected from each pen, slaughtered, and allowed to chill for 48 h at 1°C. Backfat was measured on right sides, and a sample of the LM was removed for fatty acid composition analysis. Regardless of source, inclusion of fat in swine diets did not (P 
0.349) affect ADG, ADFI, or G:F. Furthermore, carcasses from pigs fed diets formulated with 5% fat had greater (P = 0.013) average backfat depths than those from pigs fed the Ctrl diet. Live weight, carcass weight, and backfat depths increased (P < 0.001) as slaughter weight increased from 28.1 to 113.6 kg. The proportion of SFA in the LM increased (P < 0.001) with increasing slaughter weight from 28.1 to 68.1 kg, but SFA percentages were similar between 68.1 and 113.6 kg, and pigs fed the Ctrl diet had greater (P = 0.032) proportions of SFA than pigs fed SBO and PF. Moreover, the proportion of all MUFA increased (P < 0.001) 9.4 percentage units from 28.1 to 113.6 kg; however, only pigs fed SBO had lower (P = 0.004) MUFA percentages than those fed Ctrl, BT, and PF. Even though the proportion of PUFA in the LM decreased with increasing slaughter weight, pigs fed SBO had greater PUFA percentages, a higher PUFA-to-SFA ratio, and greater iodine values than all other dietary treatments when slaughtered at weights of 45.5 kg or greater (fat source x slaughter weight, P < 0.001). Results of this study indicate that fat source had little to no impact on live pig performance, but feeding a polyunsaturated fat source altered the fatty acid profile of the LM within the first 23 kg of gain, and, more specifically, including 5% SBO in swine diets could lead to economical ramifications associated with soft pork/fat.
Key Words: s: Dietary fat source • Fatty acid composition • Longissimus muscle • Performance • Pork • Slaughter weight
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J. K. Apple, C. V. Maxwell, D. L. Galloway, C. R. Hamilton, and J. W. S. Yancey Interactive effects of dietary fat source and slaughter weight in growing-finishing swine: III. Carcass and fatty acid compositions J Anim Sci, April 1, 2009; 87(4): 1441 - 1454. [Abstract] [Full Text] [PDF]
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