PSXI-15 Clove and cashew nut shell oils on the growth of ruminal gram-positive bacteria

Abstract

Abstract Livestock production efficiency is dependent on the rumen environment. Daily or long-term alterations of the rumen bacterial population can modify the degradability of feeds and the production of volatile fatty acids. This work was realized to evaluate the effect of clove (Syzygium aromaticum) and cashew nut shell (Anacardium occidentale) oils on the growth of ruminal bacteria Ruminococcus albus, Ruminococcus flavefaciens and Streptococcus bovis, gram-positive bacteria involved on carbohydrate degradation. The experiments were designed using each bacteria exposed to two different doses (0.20 and 0.02 mg/ml) of either clove or cashew nut shell oils. Bacteria were cultivated on Hobson’s M2 medium in Hungate tubes. Cultures cultivated without addition of any oils were considered as control. Bacteria were cultivated overnight and freshly inoculated into new tubes containing medium. Bacteria growth was monitored at 0, 8, 12 and 24 hours after inoculation using a spectrophotometer at 600 nm wavelength. Data were analysed using the linear mixed models and the NLME Procedure in R software. The highest concentration of cashew nut shell oil (0.2 mg/ml) decreased (P < 0.05) R. albus density by 24 hour (-38.4%) in contrast to the control treatment. R. flavefaciens had the greatest sensitivity (P < 0.05) among the tested bacteria at 12 hour to clove oil compared to the control, having a decrease in population (-10.8% and -15.9%) when doses 0.2 and 0.02 mg/ml were used, respectively. Also, R. flavefaciens showed an effect (P < 0.05) with cashew nut shell oil (0.02 mg/ml) causing a decreasing population (-2.9%) in comparison to control treatment. S. bovis was not affected by the oils. Changes in bacterial growth is likely linked to modifications in acetate:propionate ratio, which affect the ruminant feed use efficiency. In conclusion, use of clove and cashew nut shell oils influenced the tested rumen bacteria growth.