Combination of Essential Oils and Extracts Enriched with Tocopherols in Diet of Holstein Steers and Its Effect on Ruminal Fermentation, Antioxidant and Anti-Inflammatory Response, Feed Efficiency and Fatty Acid Profile in Meat

Background: This experiment evaluated whether the combination of essential oils (thyme, rosemary, orange) with extracts of Cinnamomum and Quillaja saponaria (enriched with tocopherols) in steers' diet has positive effects on the health, digestibility, growth, oxidative stress, and fatty acid profile of meat. Methods: The experiment included 24 Holstein steers, divided into two groups, randomly divided (treated = phytogenic mixture (n = 12); control = monensin (n = 12)), undergoing a growth phase of 120 days and 90 days of finishing in individual pens, with a monthly collection of blood, rumen fluid, feces, and feed. Results: In the finishing phase (days 150 to 210), there was a tendency (p = 0.07) toward more significant average daily weight gain when cattle consumed a phytogenic mixture than monensin. The use of the phytogenic product showed greater feed efficiency in the period from 150 to 240 days (p < 0.05), with higher levels of short-chain fatty acids (SCFAs), without differences in the composition of these SCFAs between the control and treated groups, with a reduction in apparent digestibility in the treated group. In blood parameters, the treated group showed higher erythrocyte counts (p < 0.05) without changes in leukocytes, lymphocytes, granulocytes, monocytes, and platelets. The phytogenic treatment demonstrated higher total protein and globulin levels, with increased glucose levels on days 30 and 210 (p < 0.05). Ceruloplasmin and haptoglobin levels increased in the treated group without changes in ferritin, transferrin, C-reactive protein, IgA, and heavy-chain immunoglobulins (p < 0.05). A reduction in oxidative stress was observed using the phytogenic agent, with a marked decrease in the levels of reactive oxygen species (ROS) and carbonyl proteins, with a tendency to increase glutathione S-transferase (p < 0.05). In meat, the phytogenic reduced saturated fatty acids with increased polyunsaturated fatty acids and increased the omega 6/omega 3 ratio. Lower levels of thiobarbituric acid reactive substances and ROS were detected in the meat combined with a higher concentration of total thiols in the treated group than in the control group. Conclusions: The use of the phytogenic in steers' diets has shown to be a viable candidate for replacing monensin, presenting equal or superior performance results with systemic modulating effects on oxidative stress, meat quality, and serum and biochemical parameters that contribute to more substantial health and efficiency.