Studies on acid oils and fatty acids for chickens III. Effect of chemical composition on metabolisable energy of by-products of vegetable oil refining.

1. Fourteen by-products of oil refining, selected for their variability in free fatty acid and unsaponifiable contents, were analysed chemically with the objective of relating the determined ME values of the products to chemical composition by means of multiple linear regression analysis. Refined sunflower oil was included as a reference fat. 2. Twenty-one 2-week-old chicks were used to determine fat digestibilities and AMEn values of diets, using the total collection method. Fats were included in a wheat-soyabean meal diet at 100 g/kg. Multiple linear regression analysis was used to express the ME values of fats as functions of the parameters measured (moisture, gross energy, impurities, unsaponifiables, non eluted material, free fatty acid content, unsaturated: saturated ratio, peroxide value, TBA test). 3. The ME of the fat products lay in the range l2.62 to 24.35 MJ/kg, and 29.26 MJ/kg for refined sunflower oil. Free fatty acid content of the fats was shown to be a poor predictor of their ME values, whereas non eluted material (NEM) of the fat products showed a good correlation with their ME. A regression equation could be derived (R2 0.6548; SEE 2.0064) with the unsaturated: saturated ratio (U:S) and NEM. An ME prediction equation based on the U:S, NEM and unsaponifiable content is also proposed (R2= 0.7l68; SEE= 1.9058).