Effects of a specific blend of essential oils on apparent nutrient digestion, rumen fermentation and rumen microbial populations in sheep fed a 50:50 alfalfa hay:concentrate diet

Six sheep fitted with ruminal fistulas were used in a repeated measurement design with two 24-d periods to investigate the effect of adding a specific mixture of essential oils (MEO) at 0 (control), 0.8 and 1.6 ml/d on apparent nutrient digestibility, rumen fermentation characteristics, rumen microbial population and blood chemical metabolites. Animals were fed with a 50:50 alfalfa hay: concentrate diet. Ruminal pH, total VFA concentration, molar proportion of individual VFA (acetate, propionate, butyrate, iso-valerate), acetate: propionate ratio and methane production were not affected with MEO. Small peptides plus amino acid nitrogen and large peptides nitrogen concentration in rumen fluid were not affected with MEO supplementation relative to those of the control; while, rumen fluid ammonia nitrogen concentration at 0 and 6 h after morning feeding in sheep fed with 1.6 ml/d of MEO was lower (P < 0.05) compared to those fed with control and 0.8 ml/d of MEO. At 0 h after morning feeding, ammonia nitrogen concentration was higher (P < 0.05) in sheep fed with 0.8 ml/d of MEO relative to that fed with 1.6 ml/d of MEO and control diet. Ruminal protozoa and hyper ammonia producing (HAP) bacteria counts were not affected by addition of MEO in the diet. For evaluated blood cells and metabolites in sheep fed diet supplemented with MEO relative to those fed the control, no changes were observed in red blood cells, white blood cell, hemoglobin, hematocrit, glucose, BHBA, cholesterol, total protein, albumin, blood urea nitrogen (BUN) and AST and ALT concentration. Apparent total tract digestibility of dry matter (DM), crude protein (CP), organic matter (OM) and nuteral detergent fiber (NDF) were not influenced by MEO supplementation. The results of the present study suggested that supplementation of MEO may have limited effects on apparent nutrient digestibility, ruminal fermentation and protozoa and HAP bacteria count, blood cells and metabolites.