Effects of sea-buckthorn flavonoids on growth performance, nutrient digestibility, microbial protein synthesis, and plasma antioxidant capacity of finishing lambs

Sea-buckthorn flavonoids (SFs) are a type of natural antioxidants that have attracted considerable attention because of their extensive biological functions and regulatory effects on animal physiology. This study evaluated the effects of dietary SFs supplementation on growth performance traits, apparent nutrient digestibility, rumen fermentation, microbial protein synthesis, and antioxidant capacity of finishing lambs. In total, forty-eight 1/2 Dorper (♂) × 1/2 Small thin-tailed (♀) crossed male lambs (body weight = 22.5 ± 1.33 kg, mean ± SD) were randomly allocated to one of the four treatment groups (n = 12 lambs/group): basal diet supplemented with 0 (CON), 1.0 (LSFs), 3.0 (MSFs), and 5.0 (HSFs) g SFs/kg diet (dry matter basis). After 60 days of feeding experiment, six lambs were randomly selected from each group for 10 days of digestion and metabolism experiment. The results showed that lambs in the MSFs group had significantly higher ADG than those in CON group (P < 0.05), and both LSFs and MSFs group had higher DMI than the other groups (P < 0.05). The digestibility of DM in MSFs group was significantly higher than that in CON group (P < 0.05), and the digestibility of OM and NDF was also higher than that in CON and HSFs group (P < 0.05). The urinary nitrogen excretion of lambs in MSFs and HSFs groups was lower than that in CON and LSFs groups, therefore, the dietary nitrogen retention was significantly increased (P < 0.05). Rumen fermentation results showed that acetate and total volatile fatty acids (VFA) concentrations in MSFs and HSFs groups were higher than those in other groups (P < 0.05), and the microbial proteins (MCP) yield in MSFs group was also significantly increased compare with the CON group. In addition, the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in plasma of lambs in MSFs and HSFs groups were significantly increased, while the content of malondialdehyde (MDA) was significantly decreased (P < 0.05). Therefore, SFs are beneficial for growth performance, rumen fermentation, and serum antioxidant capacity in lambs and could be used as a natural feed additive in lamb production.