Interactive effects of dietary fat source and slaughter weight in growing-finishing swine: I. Growth performance and longissimus muscle fatty acid composition

Pig performance was not affected by the fat source included in grower diets
Tuesday 8 September 2009 (9 years 1 months 13 days ago)
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The fatty acid composition of pork adipose and muscle tissues changes may be related to the saturation concentration of the dietary fat source and the dietary inclusion concentration of a particular fat source. Additionally, little is known about the effects of fat sources other than beef tallow on fatty acid compositional changes in the LM over time on feed. Therefore, the objective of the present experiment was to test the interactive effects, if any, of dietary fat sources incorporated into diets at 5% and slaughter weight on the fatty acid composition of the LM from growing-finishing pigs.

A total of 288 crossbred 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 BW 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 the 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. Body 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 the SBO and PF diets. Moreover, the proportion of all MUFA increased (P < 0.001) by 9.4 percentage units from 28.1 to 113.6 kg; however, only pigs fed the SBO diet had reduced (P = 0.004) MUFA percentages than those fed the Ctrl, BT, and PF diets. Even though the proportion of PUFA in the LM decreased with increasing slaughter weight, pigs fed SBO had greater PUFA percentages, a greater PUFA-to-SFA ratio, and greater iodine values than pigs fed all other dietary treatments when slaughtered at BW of 45.5 kg or greater (fat source × slaughter weight, P < 0.001).

It is concluded 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 17.4 kg of BW gain; more specifically, including 5% SBO in swine diets could lead to economical ramifications associated with soft pork or fat.

JK Apple, CV Maxwell, DL Galloway, S Hutchison and CR Hamilton. 2009. Journal of Animal Science. 87:1407-1422.

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