Abstract
Essential oils (EOs) and their active components are attracting a lot of attention as sustainable feed additives due to their known antimicrobial properties against a variety of microorganisms, including bacteria, protozoa, and fungi. They also have biological therapeutic, antioxidant, and flavor properties. They can be used for modifying the rumen environment and improving animal productivity. The present study was designed to investigate the effect of supplementation with 2.5 and 5 g/head/day of an essential oils blend (EOB) of clove, oregano, and juniper in equal proportions on milk production and quality, and physiological status of early lactating Holstein dairy cows for 8 weeks of treatment followed by 8 weeks of posttreatment. The results revealed an improvement in milk yield (p <= 0.02) and feed efficiency (p <= 0.001) with EOB at a dose of 2.5 g/head/day. The percentages of milk protein and lactose were increased (p <= 0.03) with a high dose of EOB inclusion during the treatment period as compared with the control group. Milk fat percentage, fat-corrected milk, and energy-corrected milk were not significantly affected by EOB supplementation. The supplementation of EOB tended to decrease milk total bacterial and somatic cell counts when compared to the control group. The supplementation of EOB at both doses increased serum total protein (p <= 0.02) and globulin (p <= 0.05), and decreased cholesterol level (p <= 0.001) and creatinine (p <= 0.001) as compared to the control group. Furthermore, the results show that the low dose of EOB had more desirable effects on milk yield, milk total bacterial count, milk somatic cell count, and feed efficiency than the high dose, suggesting that lower doses may not inhibit rumen microbial populations. Moreover, the low doses of EOB could be used as sustainable natural alternatives to antibiotics in livestock diets.