Effects of Oregano Essential Oil and/or Yeast Cultures on the Rumen Microbiota of Crossbred Simmental Calves.

This study hypothesized that combining oregano essential oil () and yeast cultures (s) would modulate rumen microbiota to promote gastrointestinal homeostasis and function. Twenty-four newborn, healthy, disease-free, crossbred Simmental male calves (birth weight ≥ 35 kg) were assigned to one of four treatments based on birth data. Treatments were as follows: (1) Control (), calves fed calf starter without additives; (2) , calves fed calf starter containing 60 mg/kg body weight () of OEO per day; (3) s, calves fed calf starter containing 45 mg/kg BW of YC per day; and (4) , calves fed calf starter with OEO (60 mg/kg, BW) and YC (45 mg/kg, BW) combination.

Oregano Essential Oil as a Natural Plant Additive Affects Growth Performance and Serum Antibody Levels by Regulating the Rumen Microbiota of Calves.

This experiment aimed to investigate whether supplementation of calves with different doses of oregano essential oil (OEO) could promote the development of the gastrointestinal tract and enhance the immune ability of calves by regulating the rumen microbiota. Twenty-four 70-day-old healthy and disease-free Holstein male calves were randomly divided into four groups, with the control group fed a basal diet, and the treatment group provided 4 g, 6 g, and 8 g of oregano essential oil per day in addition to the basal diet. After the 14-day pre-test, a 56-day formal test was conducted.