Effect of adding caprylic and capric acid to grass on fermentation characteristics during ensiling and in the artificial rumen system RUSITEC

Silage was prepared from grass that was treated either with caprylic or capric acid, prior to ensiling, to increase aerobic stability. The silage was introduced to the RUSITEC in order to measure the effect of treatment on in vitro microbial metabolism. Although, caprylic acid inhibited lactic acid formation during the ensiling process, aerobic stability was high. Capric acid did not interfere with lactic acid production yielding silage with moderate stability. In RUSITEC neither caprylic nor capric acid had an effect on protozoa counts, but both lowered apparently degraded organic matter (OMAD). Caprylic acid promoted methane and acetate production while propionate production and microbial yield were lower. Capric acid had no effect on the production of methane, acetate and propionate; butyrate production increased and microbial yield remained unaffected. ic and capric acid are highly preservative, yielding silage of good quality and high aerobic stability indicating their efficiency against spoilage micro-organisms. The bactericidal effect however, was modified during the ensiling process since both lost some toxicity against rumen protozoa and methanogenic bacteria. Net production of rumen microbial cell mass per unit OMAD was not impaired.