Interactive effects of dietary fat source and slaughter weight in growing-finishing swine: I. Growth performance and longissimus muscle fatty acid composition.
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 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 degrees 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 >or= 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 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 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.
Apple JK
，Maxwell CV
，Galloway DL
，Hutchison S
，Hamilton CR
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Fatty acid and energy metabolism in broiler chickens fed diets containing either beef tallow or an oil blend.
The hypothesis tested was that the feeding of n-6 polyunsaturated fatty acids (PUFA) results in more whole-body fatty acid oxidation than the feeding of saturated fatty acids (SFA). It was reasoned that the increased fatty acid oxidation would be associated with enhanced whole-body energy expenditure and stimulated de novo fatty acid synthesis. To put the hypothesis to the test, broiler chickens were fed diets containing either beef tallow as source of SFA or an oil blend as source of n-6 PUFA. The broilers either had free access to their diet or were fed a restricted amount. Seven-day-old, male broiler chickens were used; they were kept individually in cages from 1 to 4 weeks of age. In the birds fed ad libitum, the n-6 PUFA diet reduced average daily feed intake (ADFI), but did not significantly affect average daily weight gain (ADG) and the feed:conversion ratio (FCR). The lower ADFI on the n-6 PUFA diet was associated with a higher apparent digestibility of total fatty acids. The ratio of deposition in the body to intake of digestible total PUFA, which reflected n-6 PUFA, was significantly decreased by the n-6 PUFA diet, pointing at preferentially increased n-6 PUFA oxidation on the n-6 PUFA diet. The ratio for n-9 monounsaturated fatty acids (MUFA) was higher than 1.0, which agrees with net de novo synthesis, but the n-6 PUFA diet induced a lower value than did the SFA diet. Feeding either the n-6 PUFA or SFA diet did not influence energy expenditure expressed as percentage of energy intake. This study supports the idea that dietary n-6 PUFA instead of SFA are preferentially oxidized, but no proof was obtained for enhanced energy expenditure and contrary to the hypothesis put forward, the n-6 PUFA diet depressed de-novo fatty acid synthesis.
Wongsuthavas S
，Yuangklang C
，Vasupen K
，Mitchaothai J
，Alhaidary A
，Mohamed HE
，Beynen AC
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