The Effect of Essential Oils of Spearmint on the in Vitro Rumen Fermentation, Growth, and Deaminative Activity of Amino Acid Fermenting Bacteria

Abstract

The aim of this study was to assess the effect of essential oils of spearmint (SEO) on the in vitro gas production (GP) kinetics, fiber digestibility and proteolysis by rumen microbial community using Menke syringes. Asymptotic GP, half time of GP and the sigmoidisity degree of the GP curve were determined using a typical growing lamb diet. Ammonia production and in vitro fiber digestibility in response to different doses SEO was measured. The effect of this oil on the deaminative activity of mixed rumen microbes and a recently isolated amino acid-fermenting bacterium were studied. SEO decreased asymptotic GP and increased degree of sigmoidicity. While In vitro fiber digestibility was negatively affected by SEO, the concentration of ammonia in fermentation syringes increased. The tested oil inhibited ammonia production and the specific rate of ammonia production by the isolate (Clostridium SPP. MT8). Similarly, such results were observed for ammonia production by mixed rumen microbes. Overall, SEO had an antimicrobial activity and anti-proteolysis effect, and therefore modulating effect on rumen fermentation.