Effects of dietary sclareol supplementation in aged broiler breeders on production performance, egg quality, antioxidant capacity, and gut microbiota

This study evaluated the effects of sclareol on production performance, serum antioxidant indices, and gut health in late-laying Tianfu broiler breeders. Six hundred 42-week-old breeders were randomly divided into five groups: basal diet (CON), basal diet with 250 mg/kg oregano thymol (ORE), or basal diet with 200 (LSCL), 400 (MSCL), or 800 mg/kg sclareol (HSCL). Each group included eight replicates of 15 birds. Performance parameters were recorded weekly. On days 42 and 84, samples were collected to assess antioxidant capacity, digestive enzyme activity, and intestinal morphology. Compared to CON, the MSCL group exhibited a 6.3 % higher egg production rate (P < 0.05) and significantly lower cracked and deformed egg rates by 32.1 % and 28.5 % (P < 0.05) during days 42-84. Both MSCL and HSCL groups showed increased Total Antioxidant Capacity (T-AOC) and Total Superoxide Dismutase (T-SOD) activities (P < 0.05) and an 18.6 % reduction in Malondialdehyde (MDA) content (P < 0.01). The MSCL group demonstrated a 22.4 % increase in duodenal villus height and an 18.6 % higher villus-to-crypt ratio (P < 0.05), plus a 27.3 % greater jejunal lipase activity (P < 0.05). Ileal T-SOD activity increased (P < 0.05), and MDA content decreased (P < 0.01) in MSCL. FATP4 expression was upregulated in duodenum and jejunum, while SREBF-1 expression increased in jejunum and ileum (P < 0.05). Total fatty acid contents in eggs peaked in MSCL (P < 0.05). Sclareol supplementation improved intestinal morphology, nutrient digestibility, and antioxidant capacity, enhancing breeder performance, with 400 mg/kg providing optimal benefits.