Effects of Thymol, Eugenol and Malate on In vitro Rumen Microbial Fermentation

Abstract

The purpose of this study was to investigate effects of increased levels of eugenol, thymol and malate on pH and the concentrations of VFA, lactate and ammonia-N during in vitro ruminal incubation. One Hanwoo beef steer(741kg) fitted with a rumen cannula was used and fed 0.5kg/day rice straw and 10kg/day corn-based concentrate(ratio of concentrate to rice straw = 95:5 on DM basis). Three different doses of thymol, eugenol and malate were used. Treatments of the experiment were as follows: Treatments of thymol were control(1g D-glucose/40ml), T1(1g D-glucose+40mg thymol/40ml), T2(1g D-glucose+50 mg thymol/40ml) and T3(1g D-glucose+60mg thymol/40ml). Treatments of eugenol were control(1g D-glucose/40ml), E1(1g D-glucose+55mg eugenol/40ml), E2(1gD-glucose+65mg eugenol/40ml) and E3(1gD-glucose+75mg eugenol/40ml). Treatments of malate were control(1gD-glucose/40ml), M1(1gD-glucose+25mg malate/40ml), M2(1g D-glucose+50mg malate/40ml) and M3(1g D-glucose+100mg malate/40ml). The results of this study showed that eugenol and thymol have improved stability of the ruminal fermentation by decreasing lactic acid concentration and increasing ruminal pH. However, it inhibited the production of total VFA, acetate and propionate. Malate also improved stability of the ruminal fermentation by decreasing lactic acid concentration and increasing ruminal pH, but it had a very little effect on ruminal lactate concentrations and pH. On the other hand, malate did not decrease the concentrations of total VFA, acetate and propionate. Therefore, at the low ruminal pH expected in high-concentrate diets, thymol, eugenol, and malate are potentially useful in Hanwoo finishing diets. Further studies are necessary for determining the effectiveness of these additives on in vivo rumen fermentation and animal performance in Hanwoo finishing steers.