摘要:
This experiment was conducted to investigate the effects of zinc-methionine on egg quality,intestinal morphology and histological structure and cecal microbial flora to determine the scientific doses in laying hens.Five hundred and forty 20-week-old healthy Hyline White laying hens were randomly allocated to 6 groups with 6 replicates per group and 15 birds per replicate.Hens in group Ⅰ were fed a basal diet as the control,and those in group Ⅱ,Ⅲ,Ⅳ,Ⅴ and Ⅵ received the basal diets supplemented with 70,140,350,700 and 1 400 mg/kg zinc-methionine,respectively.The trail lasted for eight weeks.The results showed as follows:Compared with the control group,laying rate,daily egg mass,the ratio of feed to egg were notably increased and unqualified egg rate were significantly decreased (P<0.05),eggshell strength,eggshell thickness,albumin height and haugh unit were remarkably improved (P<0.05),villus height and ratio of villus height to crypt depth were notably increased (P<0.05),the number of Bifidobacteria and Lactobacilli was remarkably increased and the amount of Escherichia coli was notably decreased (P<0.05) in the cecal contents of laying hens in group Ⅱ and Ⅲ,however,laying rate,daily egg mass,the ratio of feed to egg were notably decreased and unqualified egg rate were significantly increased (P<0.01),eggshell strength,eggshell thickness,albumin height and haugh unit were remarkably reduced (P<0.01),villus height and ratio of villus height to crypt depth were notably decreased (P<0.01),the amount of Escherichia coli was extremely increased (P<0.01) and the number of Bifidobacteria and Lactobacilli was notably decreased (P<0.01) in group Ⅵ.Damage occurred in duodenum and ileum of hens in group Ⅵ.The results indicated that dietary supplementation with optimal doses of zinc-methionine upregulated laying performance and egg quality,improved the intestinal morphology,optimized cecal microbiota of laying hens,but continuously improving the supplemental levels would lower its positive effect and even trigger negative effects.According to the quadratic curve fitting model,the optimal supplemental level of zinc-methionine is 50~100 mg/kg in the corn-soybean meal diet of laying hens during the peak period.%本试验旨在研究饲粮中添加蛋氨酸锌对蛋鸡蛋品质、肠道形态、组织学结构及盲肠微生物菌群的影响,以确定蛋氨酸锌在蛋鸡饲粮中的科学用量.选择健康的20周龄海兰白蛋鸡540只,随机分成6个组,每个组6个重复,每个重复15只鸡.Ⅰ组为对照组,饲喂基础饲粮,试验Ⅱ、Ⅲ、Ⅳ、Ⅴ、Ⅵ组分别在基础饲粮中添加70、140、350、700、1 400 mg/kg蛋氨酸锌.正试期8周.结果表明:与对照组相比,Ⅱ、Ⅲ组产蛋率和日产蛋重显著提高(P<0.05),料蛋比和不合格蛋率显著降低(P<0.05),蛋壳强度、蛋壳厚度、蛋白高度和哈氏单位显著提高(P<0.05),十二指肠、回肠的绒毛高度和绒毛高度/隐窝深度显著提高(P<0.05),盲肠内容物中双歧杆菌、乳杆菌数量显著增加(P<0.05),大肠杆菌数量显著减少(p<0.05);而Ⅵ组产蛋率和日产蛋重极显著降低(P<o.01),料蛋比和不合格蛋率极显著升高(P<0.01),蛋壳强度、蛋壳厚度、蛋白高度和哈氏单位极显著降低(P<0.01),十二指肠、回肠的绒毛高度和绒毛高度/隐窝深度极显著降低(P<0 01),双歧杆菌和乳杆菌数量极显著减少(P<0.01),大肠杆菌数量极显著增加(P<0.01);Ⅵ组蛋鸡十二指肠和回肠结构发生损伤.由此可见,适量的蛋氨酸锌可提高蛋鸡产蛋性能和蛋品质、改善肠道形态、优化盲肠微生物区系,但继续提高添加水平会降低其对蛋鸡产蛋性能、蛋品质和肠道健康的正面效应,甚至会引起负面效应.根据二次曲线拟合模型得出蛋氨酸锌在20~27周龄蛋鸡玉米—豆粕型饲粮中的适宜添加水平为50~100mg/kg.