Effect of essential oils of Zataria multiflora on in vitro rumen fermentation, protozoal population, growth and enzyme activity of anaerobic fungus isolated from Mehraban sheep

This study was conducted to investigate the effects of different doses (0, 150, 300, 450 and 600 μg/ml) of Zataria multiflora essential oils (ZMEO) on in vitro gas production, fermentation parameters and protozoal population using rumen inocula from growing lambs fed a high concentrate diet. Gas production (GP) was recorded at 1–144 h of incubation. After 144 h, the incubation was stopped and inoculants filtered to determine dry matter disappearance (D144). In separate runs, the effects of ZMEO on total protozoal count and species distribution were studied. The main constituents of ZMEO were carvacrol (515 g/kg), p-cymene (204 g/kg) and thymol (154 g/kg). Addition of ZMEO reduced asymptotic GP, GP rate, D144 and dry matter disappearance (P < 0.001), while GP lag and half-time were increased (P < 0.001). Also GP after 24 h of incubation, ammonia production, microbial biomass and true in vitro degradability were decreased, whereas the partitioning factor increased with addition of ZMEO (P < 0.001). Total VFA was the highest at 150 μg/ml of ZMEO. Inclusion of ZMEO decreased the number of Entodinium spp., Epidinium caudatum and Epidinium ecaudatum (P < 0.001). At the doses higher than 150 μg/ml of ZMEO Isotricha spp. as well as Dasytricha spp. were completely disappeared.Light microscopy showed that the isolated fungi were similar to Neocalimastix sp. Inclusion of ZMEO entirely inhibited growth and filter paper digestion by isolated fungus. The avicelase and β-1,4-glucosidase activity in both extracellular and cell associated fractions was decreased by ZMEO (P < 0.01). It is concluded that the ZMEO has the potential to modulate ruminal fermentation and further in vivo research is needed to determine the optimal doses of ZMEO.