Inclusion of soy oil levels on the acceptability and digestibility of diets for equines

Abstract

The effects of different quantities and types of dietary fats on the digestibility of feeds for equines are complicated and not fully understood. The present work was undertaken to evaluate the acceptability and digestibility of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), and neutral and acid detergent fibers (NDF, ADF), upon increasing inclusion levels of soybean oil (SBO) (5, 10, 15 and 20%) in the concentrate portion of diets composed of equal parts of grass hay and concentrate. The total collection of feces method was used with four yearling colts. The experimental design was 4 x 4 Latin square and the data were analyzed by simple polynomic regression. The SBO showed good acceptability as all of the concentrates offered were consumed. Level of SBO inclusion in the concentrate affected (P < 0.05) OM digestibility, there being and initial increase up to a maximum of 66.7% at the 10.74% inclusion level and decreasing digestibility thereafter; in analogous fashion the digestibilities of NDF and ADF increased to maxima of 51.8% and 45.5% at SBO inclusion levels of 9.5% and 10.56%, respectively. The lower digestibilities at higher inclusion levels were presumably due to inhibitory effects of added lipid on the cecal cellulolytic microflora. Level of SBO inclusion did not significantly affect the digestibilities of DM, CP and EE, although DM digestion followed a quadratic tendency (P = 0.08) very similar to that observed for OM.