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Interactive Effects of Dietary Fat Source and Slaughter Weight in Growing-Finishing Swine: III. Carcass and Fatty Acid Compositions

J. K. Apple^*, C. V. Maxwell^*, D. L. Galloway^*, C. R. Hamilton and J. W. S. Yancey^*

^* Department of Animal Science, University of Arkansas, Fayetteville, 72701 Darling International Inc., Irving, Texas 75038

japple{at}uark.edu

Abstract

Crossbred pigs (n = 288) were used to test the interactive effects of dietary fat source and slaughter weight on dissected carcass composition and fatty acid composition of composite carcass samples. 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 (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 primal cuts from right carcass sides were dissected into muscle, fat, bone, and skin components. Then, muscle and fat tissues were ground, and random composite samples were collected from each carcass for fatty acid composition analysis. Fat source did not alter pork primal cut yields (P 0.294), nor were the percentages of carcass muscle (P = 0.213), fat (P = 0.502) and bone (P = 0.551) affected by dietary fat source. Conversely, percentages of the whole shoulder and ham decreased linearly (P < 0.001), and the percentages of loin and belly increased (P < 0.001) linearly, with increasing slaughter weight. Moreover, linear decreases (P < 0.001) in carcass muscle, bone and skin, as well as a linear increase (P < 0.05) in carcass fat, were observed as slaughter weight increased from 28.1 to 113.6 kg. Composite samples from pigs fed BT or Ctrl had greater (P < 0.05) proportions of SFA, particularly oleic and stearic acids, than those from pigs fed PF and SBO when slaughtered at 45.5, 68.1, and 90.9 kg (fat source x slaughter weight, P < 0.001). Percentages of MUFA (including palmitoleic, oleic, and cis-vaccenic acids) decreased (P < 0.05), and percentages of all PUFA, especially linoleic and linolenic acids, and iodine values increased (P < 0.05) in samples from SBO-fed pigs, as slaughter weight increased from 28.1 to 113.6 kg (fat source x slaughter weight, P < 0.001). Dietary fat source did not affect carcass composition; yet, including 5% SBO in swine diets increased the polyunsaturation of pork, which could lead to economical ramifications associated with soft pork and pork fat.

Key Words: Carcass composition • Dietary fat source • Fatty acid composition • Pigs • Slaughter weight