Effect of Rosemary on Growth Performance, Meat Quality, Fatty Acid Content, Intestinal Flora, and Antioxidant Capacity of Broilers

Rosemary (<i>Rosmarinus officinalis</i> L.) is a natural spice plant with an aromatic flavor and antioxidant properties that can help enhance the flavor and texture of food, as well as be used as an antioxidant source in pet feed. This study explored the effect of rosemary on the growth performance and antioxidant capacity of broiler chickens. In total, 144 healthy 1-day-old Arbor Acres broilers were randomly divided into four groups: The control group was fed a basic diet, while the positive control group was fed a basic diet supplemented with 30 mg/kg kitasamycin, and the treatment groups were fed a basic diet supplemental with 0.5% rosemary, or 2% rosemary. The average daily feed intake of broilers fed with 0.5% and 2% rosemary in 1-42 days was higher than that in the basal diet group (<i>p</i> < 0.05). The pH was lower in the rosemary groups than in the 30 mg/kg kitasamycin group as measured in the thigh muscle tissue (<i>p</i> < 0.05), and the monounsaturated fatty acid C17:1 heptadecanoic acid content of the 2% rosemary group was higher than that of the other groups (<i>p</i> < 0.05). With 0.5% rosemary supplementation, the activities of the serum and liver antioxidant enzymes catalase (CAT) activity and total antioxidant capacity (T-AOC) increased (<i>p</i> < 0.05); malondialdehyde content decreased (<i>p</i> < 0.05). The serum activities of CAT, total superoxide dismutase, and T-AOC increased with 2% rosemary supplementation (<i>p</i> < 0.05). The relative expression of liver antioxidant genes, the nuclear factor E2-related factor 2, glutathione catalase 1, and superoxide dismutase 1 increased (<i>p</i> < 0.05) with 0.5% rosemary supplementation. The addition of rosemary resulted in higher intestinal <i>lactobacilli</i> counts and lower <i>E. coli</i> counts. In summary, adding 0.5% or 2% rosemary to the diet improved the growth performance of Arbor Acres broilers and increased the number of intestinal probiotics, and supplementing with 0.5% rosemary yielded better results than adding 2% rosemary. This study provides valuable insights into the broader application of plant-derived antioxidants in promoting sustainable and health-focused animal farming practices.