Using soybean acid oil or its calcium salt as the energy source for broiler chickens: Effects on growth performance, carcass traits, intestinal morphology, nutrient digestibility, and immune responses

This study consisted of three experiments performed on Ross 308 broilers. The first experiment (Exp. 1) was a bioassay in which the nitrogen-corrected apparent metabolizable energy (AMEn) of soybean acid oil (SAO) and its calcium salt (CSSAO) was measured to be 37.30 and 30.36 MJ/kg, respectively. The latter two experiments evaluated SAO and CSSAO as the energy source for growing chickens. The treatments for Exp. 2 were a control diet with no added fat and six diets that were included with either SAO (1.0, 2.0, or 3.0 % [SAO1, SAO(2), and SAO(3), respectively]) or CSSAO (1.2, 2.4, or 3.6 % [CSSAO1, CSSAO(2), and CSSAO(3), respectively]) to provide similar AMEn. The AMEn contents were 11.90, 12.20, and 12.50 MJ/kg of diet in the starter (8-14 d of age), grower (15-28 d of age), and finisher (29-42 d of age) periods, respectively. The treatments for Exp. 3 were a control (as in Exp. 2) and 4 diets that were enriched with SAO (2.0 or 4.0 % [HSAO(1) and HSAO2, respectively]) or CSSAO (2.4 or 4.8 % [HCSSAO(1) and HCSSAO(2), respectively]) and formulated to be higher in AMEn than the control. The AMEn contents of the HSAO1 and HCSSAO(1) diets were 12.25, 12.55, and 12.85 MJ/kg, while the HSAO2 and HCSSAO(2) provided 12.60, 12.90, and 13.20 MJ/kg AMEn in the starter, grower, and finisher periods, respectively. In Exp. 2, a tendency to improve of overall body weight gain was recorded with the increase of SAO and CSSAO concentrations in the diet (P = 0.076). In Exp. 3, however, a rise of dietary AMEn with either fat source increased body weight gain and feed efficiency than the control during the entire period (P < 0.05). Diet inclusion with SAO or CSSAO increased the villus height and villus/crypt ratio across the small intestine and decreased the ileal crypt depth, while improved dry matter and crude protein digestibility (P < 0.05), with these differences were more marked in Exp. 3. Conversely, the ether extract digestibility tended to decrease with HSAO(2) and HCSSAO(2) diets (P = 0.104). Dietary treatments did not affect antibody titers against Newcastle-and avian influenza diseases (Exp. 2 and Exp. 3). To conclude, both SAO and CSSAO could be added as energy source to the diet while having beneficial effects on the performance and health of broiler chickens.