Acid versus crude oils for broiler chicken diets: In vitro lipid digestion and bioaccessibility

The use of acid oils and fatty acid distillates in poultry feed formulations is limited due to controversial productive results that has been partially related to a lower digestibility compared with their corresponding crude oils. In vitro digestion and bioaccessibility models mimicking fat intestinal digestion will provide valuable information to understand differences in dietary fat digestibility observed in in vivo trials. The hydrolysis processes that occur during intestinal digestion of soybean acid oil (SA: unsaturated), palm fatty acid distillate (PFAD: saturated), and their corresponding crude oils, as well as their potential bioaccessibility were studied using an in vitro digestion model. The release of lipid-class products (Triacylglycerol(s), TAG; Diacylglycerol (s), DAG; Monoacylglycerol(s), MAG; and Free fatty acid(s), FFA) was followed at 10, 30, and 60 min of digestion. In all oils studied, the largest hydrolysis rate occurred within the first 10 min. At the end, the percentages of generated lipid products were in the range of expected values according to the pancreatic lipase activity. After digestion, dietary mixed micelles (DMM) and the non-bioaccessible precipitated phase (PP) were isolated to analyze their lipid-class composition. Unsaturated oils showed higher DMM fraction than saturated ones (P = 0.001). Higher PP (P < 0.001) were generated in acid oils. Results suggested that hydrolysis did not limit oil digestion and that the oil FFA levels influenced their bioaccessibility less than the saturation degree.

Automated summary

The use of acid oils and fatty acid distillates in poultry feed formulations is limited due to lower digestibility compared with their corresponding crude oils. In vitro digestion models show that unsaturated oils have higher bioaccessibility and acid oils produce more non-bioaccessible precipitated phase. The release of lipid-class products in digestion does not limit oil digestion, and the saturation degree of oil influences bioaccessibility more than the levels of free fatty acids.