Effects of free-fatty-acid content and saturation degree of the dietary oil sources on lipid-class content and fatty-acid digestibility along the gastrointestinal tract in broilers from 22 to 37 days of age

Abstract

The aim of the present study is to assess the effect of the free-fatty-acid (FFA) content and saturation degree of dietary fat (added at 6%) on the fatty-acid (FA) digestibility and lipid-class content along the gastrointestinal tract and excreta in broilers from 22 to 37 d of age. This is essential to determine the potential use of acid oils (refining by-products rich in FFA) in broiler diets as an alternative to crude oils. The study consisted of a 2 × 4 factorial arrangement, which included 2 fat sources (soybean oils - unsaturated, or palm oils - saturated) and 4 levels of FFA (5, 15, 35, and 50%). Samples of digestive content of the gizzard, duodenum, jejunum, ileum and of the excreta were obtained at 37 d of age. Irrespective of the dietary fat source, more than 80% of total FA (TFA) was absorbed in the jejunum. Broilers fed with unsaturated diets had a higher absorption efficiency of FA than did those fed with saturated diets. This conclusion is supported by the lower FFA content and the higher TFA and polyunsaturated FA (PUFA) digestibility coefficients in the ileum (P < 0.001) observed in the former group. The dietary FFA level did not affect the FA absorption process as much as the dietary fat source did. This was supported by the lack of statistical differences among the diets with a similar saturation degree but rather different levels of FFA, for TFA, saturated FA, and PUFA digestibility coefficients both in the jejunum and ileum. However, the interactions reported in the ileum for triacylglycerol and diacylglycerol contents (P < 0.001), as well as for monounsaturated FA digestibility coefficients (P < 0.05) show that the dietary FFA content affects the FA absorption process. The present results show that the inclusion of acid oils in grower-finisher broiler diets with FFA levels up to 35% does not have a negative impact on the FA absorption process.

Keywords: acid oil; broiler; fatty-acid digestibility; free-fatty-acid; lipid class.

Figure 2

Individual fatty-acid apparent digestibility coefficients in the (A) jejunum, and (B) ileum for the four different dietary free-fatty-acid percentages (5%, 15%, 35%, and 50%) in 37-day-old broiler chickens. Values are means ± SE of 12 replicates per each dietary FFA percentage (with 3 chickens/replicate). Palmitic (C16:0), stearic (C18:0), oleic (C18:1n9), and linoleic (C18:2n6) acids. Abbreviation: FFA, free fatty acids.

Figure 1

Relation between the saturated fatty-acid digestibility calculated in the ileum, and the four dietary free-fatty-acid percentages¹ for two different fat sources (○ soybean oil -unsaturated diets, and • palm oil – saturated diets) in 37-day-old broilers. ¹Diets with an average of 5, 15, 35, and 50% of FFA. Each point represents each replicate value (with 3 chickens/replicate). The black line illustrates the quadratic model observed for the unsaturated diets: y = -3-5 × 2 – 0.006x, where R² = 0.39 and P = 0.007. The saturated diets did not fit any model. Abbreviations: FFA, free fatty acids; SFA, saturated fatty acids.