饲粮锌对高温应激雪山草鸡生长性能、营养物质表观消化率和血清生化指标的影响

Effect of Dietary Zinc on Growth Performance,Apparent Digestibility and Serum Biochemical Indices of High-temperature Stressed Xueshan Broilers

【目的】评估不同形态和剂量的锌对高温应激环境中雪山草鸡生长性能、表观消化率和血清生化指标的影响,以期为高温环境下雪山草鸡的锌营养提供参考。【方法】试验采用2(锌源)×2(锌添加水平)两因子完全随机设计,2种锌源分别为无机硫酸锌和中等螯合强度蛋白锌,2种锌添加水平分别为30和60 mg/kg,共4个试验组;另设1个满足肉鸡锌需要量的对照组。选取320只61日龄雪山草鸡,随机分配到5个组中,每个处理8个重复,每个重复8只鸡。预试期7 d,正试期28 d,均在高温应激条件下进行。分别在试验第14(75日龄)和28(89日龄)天时采集饲料样、粪样和血样,用于测定肉鸡的生长性能、养分表观消化率和血清生化指标。【结果】①锌源、锌添加水平及两因子互作对高温应激肉鸡的生长性能均无显著影响(P>0.05)。②与对照组相比,饲粮中添加锌显著提高了肉鸡粗蛋白质和粗脂肪的表观消化率(P<0.05)。锌源对干物质的消化率有显著影响,在锌源主效应上,与饲粮中添加无机硫酸锌相比,添加中等螯合强度蛋白锌显著降低了高温应激肉鸡的干物质表观消化率(P<0.05)。③与对照组相比,饲粮中添加锌显著提高了试验第14天时肉鸡血清中总蛋白、白蛋白和球蛋白含量(P<0.05),以及显著提高了试验第28天时肉鸡血清中总蛋白和白蛋白含量(P<0.05)。锌源对试验第14天时肉鸡血清中总蛋白和白蛋白含量有显著影响(P<0.05);锌水平对试验第14天时肉鸡血清中总蛋白、白蛋白和球蛋白含量,以及试验第28天时肉鸡血清中总蛋白和白蛋白含量有显著影响(P<0.05);锌源×锌水平交互对试验第14天时肉鸡血清中总蛋白含量和试验第28天时肉鸡血清中白蛋白含量均有显著影响(P<0.05),其中饲粮中添加60 mg/kg中等螯合强度蛋白锌作用效果最佳。④在锌源、锌水平和锌源×锌水平互作效应上,饲粮中添加锌对高温应激肉鸡血清中谷丙转氨酶和谷草转氨酶活性均无显著影响(P>0.05)。⑤与对照组相比,饲粮中添加锌显著提高了试验第14天时肉鸡血清中总胆固醇和高密度胆固醇含量,显著降低了试验第28天时肉鸡血清中总胆固醇和低密度胆固醇含量(P<0.05)。锌水平对肉鸡血清中总胆固醇、高密度胆固醇和低密度胆固醇含量均有显著影响(P<0.05)。【结论】在高温应激条件下,饲粮中添加锌虽然没有显著改善肉鸡的生长性能,但对肉鸡粗蛋白质和粗脂肪的表观消化率产生了显著影响,并对高温应激肉鸡血清蛋白质和脂代谢指标产生有益影响,有助于维持肉鸡生理功能的稳定性。

【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 32061-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】①The 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).②Compared 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).③Compared 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.④In 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).⑤Compared 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.