Inclusion of Different Levels of Eucalyptus Oil: An In Vitro Trial to Study the Effect on Sheep Rumen Methanogenesis and Fermentation Processes

Abstract

An in vitro trial was conducted in fermentation vessels under anaerobic conditions using composite feed-1 and composite feed-2 with inclusion of different levels of Eucalyptus oil (EO) along with buffered rumen liquor of sheep to observe the effects of oil on rumen methanogenesis and fermentation. The CF-1 consisted of 40% of concentrate and CF-2 had 25 % of concentrate. The various concentrations of EO used in present study were 0.5,1 and 2 µl/ml. During the present investigation it was observed that on increasing concentration of EO in CF-1 and CF-2 resulted in linear decrease in total gas production up to 74.26% in CF-1; and 31.01% by inclusion of EO in CF-2, respectively. The findings suggest that decrease in total gas production and methane concentration was highly pronounced in CF-1 compared to CF-2. The rumen digestibility in CF-1 and CF-2 also decreased significantly (p < 0.01) from control. A significant decrease in NH3 –N compared to control was also documented. As EO in both the feeds was found to inhibit deamination activity, the ammonia production decreased with increase in the efficiency of protein utilization. The inclusion of the oil decreased the Total Volatile Fatty Acids (TVFA) concentration significantly (p < 0.01). The A:P ratio increased by inclusion in CF-2 but not in CF-1. The pH was effected on inclusion of EO in CF-2 whereas inclusion of EO in CF-1 exhibited non significant effect. Therefore, the difference in Volatile Fatty acids (VFA) pattern due to essential oil might be because of different diets and pH in different experiments. The inclusion of EO decreased the protozoa number significantly (p < 0.01). EO was found to decrease fermentation in a manner that even at 0.5 µl/ml concentration there was a significant decrease in GP, ME, SCFA, TDDM and MBP. It could therefore be envisaged that increasing the proportion of concentrate in diets and using EO as a feed additive increases the rumen efficiency by reducing the methane concentration and gas production.