De novo fatty acid synthesis and balance of fatty acids of pigs fed different fat sources

Dietary fatty acid composition has been shown to influence fat deposition in rodents, chickens and pigs. Results in pigs, however, have been less clear than in other species and may relate to the level of fat/oil added to the diet and the reporting of gross carcass composition instead of gravimetrically measured fat content. The objectives of the experiment were to study the effect of dietary fat composition on whole pig (carcass + viscera) fatty acid (FA) composition and to perform a whole-body balance in order to study de novo FA synthesis and the fate of essential FA. Seventy crossbred gilts (61.8 +/- 5.2 kg BW) were divided into 10 animals per treatment. Pigs were fed one of seven treatments: a semi-synthetic diet formulated to contain a very low level of fat (NF) and six fat supplemented diets (10%) based on a barley-soybean meal. The supplemental fats were tallow (T), high-oleic sunflower oil (HOSF), sunflower oil (SFO), linseed oil (LO), blend (FB) (55% tallow, 35% sunflower oil, and 10% linseed oil) and fish oil blend (FO) (40% fish oil and 60% linseed oil). In addition, 5 pigs were killed at 61.8 kg to measure body composition at the start of the balance period. Carcass and viscera fat content and FA composition were determined to perform a balance in pigs growing from 61.8 to approximately 100 kg BW. Whole-body FA composition reflected dietary treatments: viscera showed a high content of long-chain polyunsaturated fatty acids. Whole-body fat content of HOSF (26.7%) and SFO (26.7%) fed animals was higher than T (22.9%) fed animals (P<0.05). The ratio of de novo FA synthesis (endogenous FA) of pigs fed the very low fat diet was 1.6:1.0:3.0 for palmitic, stearic and oleic acids, respectively. The different diets containing high amounts of polyunsaturated FA (SFO, LO and FO) showed deposition ratios (not catabolizated exogenous FA) of linoleic and linolenic acids between 64.8 and 66.5, and 62.9 and 64.1%, respectively, whereas deposition rates of arachidonic, eicosapentaenoic and docosahexaenoic acids were 33.6, 47.9 and 48.9%, respectively. Tissue content of eicosapentaenoic acid and arachidonic acid increased in the diets containing high levels of linolenic and linoleic acids (P<0.05), respectively, but the diet containing high linolenic acid did not increase docosahexaenoic acid deposition (P<0.05). In conclusion, dietary tallow lowers whole animal fat content as compared to sunflower oil and high-oleic sunflower oil diets. (C) 2010 Elsevier B.V. All rights reserved.