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Influence of dietary fat source and feeding duration on pig growth performance, carcass composition, and fat quality
A total of 160 finishing pigs (PIC 327×1050; initially 45.6 kg) were used in an 84-d experiment to evaluate the effects of dietary fat source and feeding duration on growth performance, carcass characteristics, and fat quality. Pigs were blocked by sex and BW with 2 pigs per pen and 8 pens per treatment. Dietary treatments included a corn-soybean meal control diet with no added fat or a 3 × 3 factorial with main effects of fat source (4% tallow, 4% soybean oil, or a blend of 2% tallow and 2% soybean oil) and feeding duration (d 0 to 42, 42 to 84, or 0 to 84). One pig was identified in each pen on d 0, and biopsy samples of the back, belly, and jowl fat were collected on d 0, 41, and 81. On d 84, all pigs were harvested with carcass characteristics measured, and back, belly, and jowl fat samples collected. Overall, there were no differences between fat sources for growth and carcass measurements; however, pigs fed added fat diets from d 0 to 84 had improved (P<0.04) G:F compared with pigs fed the control. Pigs fed added fat throughout the entire study also had improved (P<0.04) ADG and G:F and heavier d-84 BW (P<0.01) compared with pigs fed added fat for only period 1 or 2. Adding fat for the entire study increased (P<0.03) backfat and tended to reduce (P<0.08) fat-free lean index compared with pigs fed the control. Added fat also increased (P<0.05) iodine value (IV) compared with pigs fed the control. Jowl fat, unlike the other two fat depots, did not show a period effect of IV when adding dietary fat. Increasing the feeding duration of soybean oil or a blend of soybean oil and tallow decreased monounsaturated and increased polyunsaturated fatty acids relative to feeding tallow (duration × fat source interaction, P<0.05), with the greatest changes in C18:1 and C18:2. In conclusion, feeding added fat improved ADG and G:F; however, feeding soybean oil for an increasing duration, either alone or in a blend with tallow, negatively affected the fatty acid composition and IV of finishing pigs.
Keywords: fat source, finishing pig, iodine value