Abstract: 【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.

Key words: heat-stress; slow-release urea; rumen-protected glucose; sheep; performance; rumen fermentation