Abstract: 【Objective】Oxidative stress is widespread in livestock production. Lot of factors can induce oxidative stress, among which heat stress is an important factor. Oxidative stress can influence animal growth performance and even cause death, leading to serious economic losses. Recently, plant polyphenols are getting ever growing attention for their biological functions. The aims of this study were to investigate the effects of different doses of polyphenolic extract from involucres of Castanea mollissima Blume (PICB) on broiler growth performance and antioxidant properties. 【Method】 The experiments were divided into two trials: in trial 1, 400 one-day-old male Abor Aerec (AA) broilers were randomly assigned into 5 groups (4 replicates / group, 20 chicks / replicate): Group I was used as normal control group and the broilers were fed with basic ration; broilers in group II were fed with basic ration with a supplementation of 0.15% 2,6-Ditert butyl-4 methyl phenol (BHT) premix (containing 0.015% effective BHT); broilers in group III-V were fed with the basic ration with an addition of 0.2%,0.3% and 0.4% of PICB, respectively. Intrial 1, The trial lasted for 42 days under normal temperature condition. The broilers were reared according to the AA boilers feeding and immunity programs. The body weights and feed intake were measured every week for monitoring broilers growth performance. In trial 2, 400 28-day-old male AA chicks were randomly assigned into groups described in trial 1. After one week’s adaptation under normal temperature condition, heat stress was applied for 7 consecutive days for all groups. On 3rd and 7th day of heat stress, the chicks were slaughtered and sampled. Growth performance, slaughtering parameters and anti-oxidative parameters were measured to evaluate the effects of PICB on broilers under heat stress condition. 【Result】 Trial 1 showed that under normal temperature conditions, the supplementation of PCIB had no significant effects on chick growth performance (P＞0.05). In Trial 2, the body weights of groups Ⅳ and Ⅴ were significantly higher than that of group I under heat stress condition. Compared with groups I, II, and III, group IV had significantly improved average daily gain and average daily feed intake (P＜0.05). Feed conversion ratio of groups IV and V was significantly lower than that of group I (P＜0.05). The mortality among groups tended (P=0.059) to be significant and that of group V was the lowest. The slaughtering parameters had no significant differences among groups. For broilers heat stressed after three days, total antioxidant capacity (T-AOC) in serum was not significantly different among groups even though there were some oscillations. Total superoxide dismutase (T-SOD) of group IV was significantly higher than that of group I (P＜0.05). Serum malondialdehyde (MDA) contents of different groups were significantly different. The similar situation was also for GSH-Px except for group III significantly higher than group V (P＜0.05). 【Conclusion】 Dietary PICB supplementation had no effect on growth performance of AA broilers under normal temperature condition. While under heat stress conditions 0.3% PCIB addition can significantly improve the antioxidant capacity and growth performance of broilers and mitigate the adverse effects of heat stress.

Key words: chestnut involucres polyphenols, AA broiler, growth performance, antioxidant parameters