Abstract: 【Objective】 This study aimed to investigate the effects of proline supplementation on growth performance,serum antioxidant and immune indices,and cytokine levels in weaned foals,so as to provide a reference for the healthy growth and development in foals. 【Method】 A total of 28 healthy and 5 months of age weaned foals with similarly weight were randomly assigned to four groups.Foals in control group were fed standard diet,and foals in trial groups Ⅰ,Ⅱ,and Ⅲ were supplemented with 20,40,and 60 mg/kg BW proline,respectively.The pre-feeding period was 7 d,and the experimental period was 60 d.The growth performance,antioxidant index and immune index,and cytokine contents in serum of foals were determined every 30 days. 【Result】 Compared with control group,①With the increase of proline supplementation,there was a significant growth trend of body weight in foals,the total weight gain and average daily gain of foals in group Ⅲ were significantly increased (P＜0.05).On days 0 and 60,proline supplementation exhibited an upward trend in body height,body length,chest girth,and tube girth of foals (P＞0.05).From days 31 to 60,there was a significant increase in body height growth of foals in group Ⅲ (P＜0.05).②On days 30 and 60,the activities of superoxide dismutase (SOD),glutathione peroxidase (GSH-Px),and catalase (CAT),and total antioxidant capacity (T-AOC) in serum of foals in each experimental group were extremely significantly increased (P＜0.01),while the levels of diamine oxidase (DAO) and malondialdehyde (MDA) in serum were extremely significantly decreased (P＜0.01).③On days 30,the concentrations of immunoglobulin A (IgA) and IgG in serum of foals in groups Ⅱ and Ⅲ,and IgM concentration in group Ⅲ,were extremely significantly increased (P＜0.01).On days 60,the IgM concentration of foal serum in group Ⅱ was extremely significantly increased (P＜0.01),and the concentrations of IgA and IgG in group Ⅰ were significantly increased (P＜0.05).④On days 30 and 60，the contents of tumor necrosis factor-α (TNF-α),interferon-γ (IFN-γ),interleukin-1β (IL-1β),IL-6,and IL-8 in serum of foals in each experimental group were extremely significantly decreased (P＜0.01). 【Conclusion】 Under the conditions of this experiment,proline supplementation showed a trend of improving the growth performance in weaned foals,enhancing the antioxidant capacity and immune indices,and reducing the contents of cytokines in serum.The best effect was observed at a dosage of 60 mg/kg BW.

Key words: foals; proline; growth performance; antioxidant; immunity; cytokines