Effect of unsaturated fatty acids on cellulose degradation and fermentation characteristics by mixed ruminal microbes

This experiment was conducted to evaluate the effects of supplemental unsaturated fatty acids (UFA) on fermentation characteristics, especially on gas production, cellulose degradation and volatile fatty acid (VFA) concentration by mixed ruminal microorganisms. In order to attain this objective, unsaturated fatty acids including oleic acid (C18:1), linoleic acid (C18:2) and arachidonic acid (C22:4) were added at varying level. Mixed ruminal microbes used in this experiment were obtained from the rumen of a cannulated Holstein cow. Medium pH values after 7 d incubation were significantly affected by type and level of unsaturated fatty acids (p<0.01). All of UFA inhibited total gas production, and especially treatment of arachidonic acid at the levels of 0.01% gave the lowest gas production after 7 d incubation (p<0.01). Comparison of the population of protozoa revealed that UFA did not have any significant effect on the total protozoa number. The addition of UFA did not effect dry matter degradation. Volatile fatty acid (VFA) composition of the culture was influenced little by UFA, although the considerable amount of iso-type VFA were detected in UFA supplemented incubations. The ratio of acetic acids to propionic acids, however, was lower than control in all the treatments after 7 d incubation (p<0.01).