过瘤胃葡萄糖和缓释尿素对热应激绵羊生产性能及瘤胃发酵功能的影响

【目的】 本试验旨在研究饲粮中添加缓释尿素（SRU）和过瘤胃葡萄糖（RPG）对热应激绵羊生产性能和瘤胃发酵功能的影响。【方法】 选取40只健康、体重相近的3月龄湖羊公羔，按初始体重随机分成4个处理组（n=10），分别为对照组（CON组，饲喂基础饲粮）、缓释尿素组（SRU组，基础饲粮中添加缓释尿素15 g/d）、过瘤胃葡萄糖组（RPG组，基础饲粮中添加过瘤胃葡萄糖10 g/d）和联合添加组（UG组，基础饲粮中添加缓释尿素15 g/d+过瘤胃葡萄糖10 g/d），预饲期15 d，正饲期50 d。在正饲期的最后一天晨饲前，分别采集血液和瘤胃液，测定血样中免疫球蛋白A （IgA）、免疫球蛋白M （IgM）、免疫球蛋白G （IgG）、肿瘤坏死因子-α（TNF-α）、白细胞介素-2（IL-2）的含量，并测定瘤胃液pH、氨态氮、微生物蛋白及挥发性脂肪酸等指标。【结果】 与CON组相比，①饲粮中添加缓释尿素、过瘤胃葡萄糖均显著降低热应激绵羊的呼吸频率（P<0.05），UG组热应激绵羊的直肠温度显著降低（P<0.05）。②SRU组、RPG组、UG组热应激绵羊的终末体重和平均日增重均显著提高（P<0.05），料重比显著降低（P<0.05）。③RPG组和UG组热应激绵羊血清中IgG和IgM的含量均显著提高（P<0.05），血清中TNF-α和IL-2的含量显著降低（P<0.05）。④各处理组热应激绵羊瘤胃内乙酸与丙酸的比值均显著提高（P<0.05），SRU组瘤胃内乙酸、异丁酸、异戊酸比例和总挥发性脂肪酸的浓度均显著提高（P<0.05），RPG组瘤胃液pH和异戊酸比例均显著提高（P<0.05），瘤胃内氨态氮、丙酸、丁酸的比例均显著降低（P<0.05），UG组瘤胃内乙酸、总挥发性脂肪酸及微生物蛋白的含量均显著提高（P<0.05）。【结论】 饲粮中添加缓释尿素、过瘤胃葡萄糖显著提高了热应激绵羊的生产性能，改善瘤胃发酵，维持瘤胃内环境的稳定，可有效缓解绵羊热应激。

Effects of Rumen-protected Glucose and Slow-release Urea on Performance and Rumen Fermentation Function of Heat-Stressed Sheep

【Objective】 This study was conducted to investigate the effects of slow-release urea (SRU) and rumen-protected glucose (RPG) supplementation on performance, serum biochemical indices and rumen fermentation of heat-stressed sheep.【Method】 A total of forty 3-month-old Hu male lambs with similar body weight were randomly selected and were divided into 4 groups equally (n=10):Control group (CON group, fed a basal diet), slow release urea group (SRU group, fed a basal diet supplemented with 15 g/d slow release urea), rumen-protected glucose group (RPG group, fed a basal diet supplemented with 10 g/d rumen-protected glucose), urea and glucose group (UG group, fed a basal diet supplemented with 15 g/d slow-release urea and 10 g/d rumen-protected glucose).The feeding experiment was lasted for 55 days with 15 d of adaptation and followed by 50 d for trial period.Before morning feeding on the last day of normal feeding period, blood and rumen fluid were collected, and the contents of immunoglobulin A (IgA), immunoglobulin M (IgM), immunoglobulin G (IgG), tumor necrosis factor-α (TNF-α) and interleukin-2 (IL-2) in blood samples were determined.pH, ammonia nitrogen, microbial protein and volatile fatty acid in rumen fluid were measured.【Result】 Compared with CON group, ①The respiratory rate of heat stress sheep was significantly decreased in both SRU and RPG groups, the rectal temperature of heat stress sheep was significantly decreased in UG group (P<0.05).②The final body weight and average daily gain of heat stressed sheep in SRU, RPG and UG groups were significantly increased (P<0.05), and the feed to gain ratio was significantly decreased (P<0.05).③The contents of IgG and IgM in serum of heat stressed sheep in RPG and UG groups were significantly increased (P<0.05), and the contents of TNF-α and IL-2 in serum were significantly decreased (P< 0.05).④The ration of acetic acid to propionic acid in the rumen was significantly increased in the three treatment groups (P<0.05), the content of total volatile fatty acid and proportions of acetic acid, isobutyric acid and isovalerate acid in the rumen were significantly increased in SRU group (P<0.05).The pH of rumen fluid and proportion of isovalerate acid were significantly increased in RPG group (P<0.05), while the content of ammonia nitrogen and proportions of propionic acid and butyric acid in the rumen were significantly decreased in RPG group (P<0.05).The contents of the proportion of acetic acid and total volatile fatty acid and microbial protein in the rumen were significantly increased in UG group (P<0.05).【Conclusion】 The growth performance and rumen fermentation could be improved, the stability of rumen environment was maintained, and heat stress was effectively relieved in lambs fed diets supplemented with slow-release urea and rumen-protected glucose.