Abstract: 【Objective】 The aim of this study was to assess the effect of diverse forms and doses of zinc on the growth performance,apparent digestibility and serum biochemical indices of Xueshan broilers subjected to high-temperature stress conditions,so as to provide a reference for zinc nutrition of Xueshan broilers in high-temperature environments. 【Method】 The experiment employed a 2 (zinc sources)×2 (zinc supplementation levels) completely randomized factorial design.The 2 zinc sources were inorganic zinc sulphate and moderate chelated zinc proteinate,and 2 zinc supplementation levels were 30 and 60 mg/kg,resulting in a total of four experimental groups.In addition,a control group was established to meet the zinc requirement of broilers.A total of 320 61-day-old Xueshan broilers were randomly divided into five groups,with eight replicates per treatment and eight birds per replicate.The pre-trial period was 7 d,followed by a formal trial period of 28 d,both conducted under high-temperature stress conditions.Samples of feed,faeces and blood were collected on days 14 (75 days of age) and 28 (89 days of age) of experiment for determining the growth performance,apparent digestibility of nutrients and serum biochemical indices of broilers. 【Result】 ① The zinc source,zinc supplementation level and their interaction had no significant effect on the growth performance of broilers under high-temperature stress (P＞0.05).② Compared with control group,dietary zinc supplementation significantly increased the apparent digestibility of crude protein and crude fat in broilers (P＜0.05).The zinc source had a significant effect on the digestibility of dry matter.In the main effect of zinc source,the addition of moderate chelated zinc proteinate significantly decreased the apparent digestibility of dry matter in high-temperature stressed broilers compared with the addition of inorganic zinc sulfate (P＜0.05).③ Compared with control group,dietary zinc supplementation significantly increased the serum levels of total protein,albumin and globulin in broilers on days 14 of the experiment (P＜0.05),and significantly increased the serum levels of total protein and albumin in broilers on days 28 of the experiment (P＜0.05).The zinc source had a significant effect on serum total protein and albumin levels in broilers on days 14 of the experiment (P＜0.05).The zinc level had a significant effect on serum total protein,albumin and globulin levels on days 14,as well as total protein and albumin levels on days 28 of the experiment (P＜0.05).The interaction between zinc source and zinc level had a significant effect on serum total protein levels on days 14 and serum albumin levels on days 28 in broilers (P＜0.05).Among these,the addition of 60 mg/kg moderate chelated zinc proteinate in the diet showed the best effect.④ In the terms of zinc source,zinc level and their interaction,dietary zinc supplementation had no significant effect on the activities of serum alanine aminotransferase and aspartate aminotransferase in high-temperature stressed broilers (P＞0.05).⑤ Compared with control group,dietary zinc supplementation significantly increased the serum levels of total cholesterol and high-density lipoprotein cholesterol in broilers on days 14 of the experiment,and significantly decreased the serum levels of total cholesterol and low-density lipoprotein cholesterol in broilers on days 28 of the experiment (P＜0.05).The zinc level had a significant effect on the serum levels of total cholesterol,high-density lipoprotein cholesterol and low-density lipoprotein cholesterol in broilers (P＜0.05). 【Conclusion】 Despite the absence of a notable effect on the growth performance in broilers under high-temperature stress conditions,dietary zinc supplementation demonstrated a substantial influence on the apparent digestibility of crude protein and crude fat in broilers.Additionally,it exhibited a favorable effect on serum protein and lipid metabolism indices in high-temperature stressed broilers,thereby contributing to the maintenance of physiological stability.

Key words: zinc; high-temperature stress; Xueshan broilers; growth performance; apparent digestibility; serum biochemical indices