Determination of the Apparent Metabolizable Energy of the Different Types of Soy Oil in Poultry
A trial was conducted to determine the AME concentration of soybean oil (SO), recycled soy bean oil (RSB) and acidulated soy oil soapstocks (ASO) in 35 wk-old Hy-Line W-66 cocks. There were 4 experimental diets that consisted in a basal diet based on corn and soybean meal and 3 additional diets that resulted from the combination of 95% of the basal diet and 5% of the corresponding experimental oils. Each of the 4 treatments was replicated 6 times and the experimental unit was an individual rooster. Oils were analyzed for major quality parameters (peroxide index, free fatty acid content, oleic acid index, MIU, and fatty acid profile). The AME of the oils was estimated by difference in AME between the basal and the experimental diets and then extrapolating to 100% dietary fat, and by multiplying the gross energy of the oil by its apparent digestibility coefficient. The chemical composition of the 3 oils fitted expected value with higher free fatty acid content, peroxide index, and MIU content for the ASO and lower for the SO, with the RSO being intermediate. Also, linoleic acid content was higher for SO than for ASO with RSO being intermediate. The AME of the oils obtained from the GE and the digestibility was higher for SO and RSO than for ASO (8.916, 8.880, and 7.849 kcal/kg, respectively; P < 0.05). When AME was calculated by difference between AME of the diets, the same trend was observed although the energy values of the oils were slightly higher (9.137, 8.956, and 7.961 kcal AME/kg oil for SO, RSO, and ASO, respectively; P < 0.05). It is concluded that ASO has less energy content than RSO and SO but that the three sources of soy oil, if correctly processed and evaluated, can be used as energy sources in diets for poultry.