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This Article Full Text (PDF) All Versions of this Article: jas.2008-1454v1 87/4/1423    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Apple, J. K. Articles by Yancey, J. W. S. Search for Related Content PubMed PubMed Citation Articles by Apple, J. K. Articles by Yancey, J. W. S.

Interactive Effects of Dietary Fat Source and Slaughter Weight in Growing-Finishing Swine: II. Fatty Acid Composition of Subcutaneous Fat

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 the fatty acid composition of s.c. fat. Pigs were blocked by initial BW (0 = 28.1 kg), and, within blocks, pens (8 pigs/pen) were randomly assigned to either 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, within 1 h postmortem, samples of backfat were removed from each carcass between the 4^th and 8^th thoracic vertebra, and separated into the inner, middle and outer layers for fatty acid composition analysis. During the first 17.4 kg of BW gain, percentages of all SFA increased over 4% in s.c. fat from pigs fed Ctrl and BT, but decreased 4.4 and 7.7% in pigs fed PF and SBO, respectively (fat source x slaughter weight, P < 0.001). Proportions of all MUFA in s.c. fat from BT-fed pigs increased 6.1% during the first 17.4 kg of BW gain, but MUFA levels in SBO-fed pigs decreased 9.1% between 28.1 and 45.5 kg (fat source x slaughter weight, P < 0.001). Conversely, percentages of all PUFA from SBO-fed pigs increased 39.9%, while PUFA levels in BT-fed pigs decreased 12.6%, as slaughter weight increased from 28.1 to 45.5 kg (fat source x slaughter weight, P < 0.001). Resultant iodine values (IV) of s.c. fat from SBO-fed pigs increased (P < 0.05) from 73.5 to 85.2 within the first 17.4 kg of BW gain, and remained elevated above their contemporaries fed Ctrl, BT or PF diets at each subsequent slaughter weight (fat source x slaughter weight, P < 0.001). The inner backfat layer had the greatest (P < 0.05) proportions of all SFA and the lowest (P < 0.05) proportions of all PUFA, whereas the outer layer had the lowest (P < 0.05) percentages of all SFA, but the greatest (P < 0.05) percentages of all MUFA. And, even though the middle and outer s.c. fat layers had similar (P > 0.05) levels of PUFA, the greatest (P < 0.05) and lowest (P < 0.05) IV were in the outer and middle layers, respectively. As expected, fat source included in swine diets was responsible for the fatty acid compositional changes in s.c. fat; yet, results of this study indicate that feeding 5% SBO dramatically increases the polyunsaturation of s.c. fat within the first 17.4 kg of BW gain, with backfat IV exceeding 80 thereafter.

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