ABSTRACT An experimental study was conducted to examine the effects of adding serine-protease from Bacillus licheniformis on performance and physiological parameters of broiler chickens under Egyptian condition. A total of 600 one-day-old chicks were randomly divided into four experimental treatments. The treatments consisted of the control diet with 0, 100, 200 and 300 mg/kg serine-protease. Protease supplementation increased (P < 0.05) body weights (BW). Feed conversion ratio (FCR) was improved (P < 0.05) due to 200 and 300 mg/kg protease supplementation. The dry matter and crude protein digestibilities were enhanced (P < 0.05) by both 200 and 300 mg/kg protease supplementation. Plasma albumin and high-density lipoprotein (HDL) concentrations were increased (P < 0.05), while plasma total cholesterol (CHO) and low-density lipoprotein (LDL) concentrations were decreased (P < 0.05) at 100, 200, and 300 mg/kg of protease. Liver malondialdehyde (MDA) levels were declined (P < 0.05) due to 200 and 300 mg /kg protease supplementation. Supplementing 100, 200, and 300 mg/kg of protease increased (P < 0.05) lysine, methionine, and threonine levels in breast muscle. In conclusion, exogenous serine-protease could be used as a feed additive in broiler nutrition and supplementing 200∼300 mg/kg was sufficient to improve growth performance, probably because of its mechanism to enhance protein digestibility.

中文翻译：

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补充地衣芽孢杆菌丝氨酸蛋白酶对肉鸡生长性能及生理变化的影响

摘要 进行了一项实验研究，以检查在埃及条件下添加地衣芽孢杆菌丝氨酸蛋白酶对肉鸡生产性能和生理参数的影响。600只1日龄雏鸡随机分为4个试验组。处理包括含有 0、100、200 和 300 mg/kg 丝氨酸蛋白酶的对照饮食。蛋白酶补充剂增加 (P < 0.05) 体重 (BW)。由于添加了 200 和 300 mg/kg 的蛋白酶，饲料转化率 (FCR) 得到了改善（P < 0.05）。添加 200 和 300 mg/kg 蛋白酶后，干物质和粗蛋白的消化率均提高（P < 0.05）。血浆白蛋白和高密度脂蛋白 (HDL) 浓度增加（P < 0.05），而血浆总胆固醇 (CHO) 和低密度脂蛋白 (LDL) 浓度在 100、200 和 300 mg/kg 蛋白酶时降低（P < 0.05）。由于补充 200 和 300 毫克/千克蛋白酶，肝脏丙二醛 (MDA) 水平下降（P < 0.05）。补充 100、200 和 300 mg/kg 的蛋白酶会增加（P < 0.05）乳房肌肉中的赖氨酸、蛋氨酸和苏氨酸水平。综上所述，外源丝氨酸蛋白酶可作为肉鸡营养中的饲料添加剂，添加200～300 mg/kg足以改善生长性能，可能是因为其具有提高蛋白质消化率的机制。补充 100、200 和 300 mg/kg 的蛋白酶会增加（P < 0.05）乳房肌肉中的赖氨酸、蛋氨酸和苏氨酸水平。综上所述，外源丝氨酸蛋白酶可作为肉鸡营养中的饲料添加剂，添加200～300 mg/kg足以改善生长性能，可能是因为其具有提高蛋白质消化率的机制。补充 100、200 和 300 mg/kg 的蛋白酶会增加（P < 0.05）乳房肌肉中的赖氨酸、蛋氨酸和苏氨酸水平。综上所述，外源丝氨酸蛋白酶可作为肉鸡营养中的饲料添加剂，添加200～300 mg/kg足以改善生长性能，可能是因为其具有提高蛋白质消化率的机制。