An in vitro and in situ evaluation of a diet for cattle added with organic oils

Abstract

Objective: To perform in vitro and in situ evaluation of a diet for dairy cattle at different rates of fish oil and soybean oil. Design /methodology /approach: Four treatments with different rates of fish oil (FO) and soybean oil (SO) were evaluated (Control: no added oil; diet 1: 2% FO; diet 2: 2% FO and 1.5% SO; diet 3: 2% FO and 3% SO). In vitro digestibility and in situ degradability were evaluated. Ammonia nitrogen, lactic acid, volatile fatty acids (VFAs), and microbial protein were determined. For the in situ evaluation, a protein degradability kinetic was carried out. The means were compared using a Tukey test at a 5% confidence level. Results: The proposed diets increased gas production in in vitro kinetics, as the addition of oils increased (p<0.001) and the kinetic latency time decreased (p<0.001). All diets decreased the production of short-chain fatty acids (p<0.001). The production of ammonia nitrogen and lactic acid did not differ compared to the control (p<0.05). Diet 3 had a higher production of propionic acid in comparison to diet 1 and 2. In the in situ kinetic, the "kd" rate increased as more oils were added. Study limitations/implications: Although all treatments increased the production (milliliters) of and , the gas production had a proportional increase, as a result of a better use of the diets. Findings/conclusions: The addition of oils produced changes in the fermentation patterns and in the degradation of the protein at the ruminal level, increasing bypass protein. This offers an opportunity to improve performance in certain production situations