Abstract:

We investigated the effects of soybean （Glycine max） straw co-fermented with a bacterium-enzyme mixture on the growth performance， serum indexes， and rumen microorganisms of Hu sheep. Forty-eight healthy male Hu lambs ［（27.00±2.00） kg］ aged 4 months were randomly assigned into four groups， with three replicates in each group and four lambs per replicate （stall）. Lambs in the control group were fed with a basal diet （Group C）， and those in the trial groups were fed with the basal diet with 33% （Group 1）， 66% （Group 2）， and 100% （Group 3） of the original soybean straw substituted with fermented soybean straw. The experimental period included 7 days of pre-experiment and 60 days of formal experiment. The main results were as follows： Compared with Group C， Group 2 showed a significantly decreased average daily matter intake and feed-to-gain ratio during days 1-30 and 1-60 （P<0.05）. The serum contents of albumin， glutamic pyruvic transaminase， high density lipoprotein， and total cholesterol were significantly higher in Group 3 than in the control （P<0.05）. The globulin contents were significantly higher in Groups 2 and 3 （P<0.05）， and the total protein content and glutamic oxaloacetic transaminase activity were significantly higher in all trial groups （P<0.05） than in the control. The activity of superoxide dismutase in serum was increased significantly in Group 3 （P<0.05）， and catalase and glutathione peroxidase activities in serum were increased significantly in all trial groups （P<0.05） compared with the control. The serum immunoglobulin （Ig） A content was increased significantly in all trial groups （P<0.05）， and the serum IgG and IgM contents were increased significantly in Groups 2 and 3 （P<0.05）， compared with the control. Compared with the control， Group 2 significantly increased apparent digestibility of crude protein， acid detergent fiber and neutral detergent fiber （P<0.05）； significantly increased rumen isobutyric acid and ammonia nitrogen （NH₃-N） contents （P<0.05）； and significantly decreased valeric acid content （P<0.05）. In terms of the bacterial community in the rumen， at the phylum level， the abundance of rumen Bacteroidota wasincreased （P<0.05）， while that of Firmicuteswas decreased （P<0.05） in Group 2 compared with the control. At the genus level， the abundance of Prevotellaceae_UCG-001 was significantly higher in Group 2 than in the control （P<0.05）. In conclusion， the addition of bacterium-enzyme co-fermented soybean straw to the diet can improve the antioxidant and immune capacity， nutrient apparent digestibility， the rumen environment， and the rumen microbial community structure of Hu sheep. These results provide a scientific basis for the application of fermented soybean straw in the production of Hu sheep.

Key words: Hu sheep, growth performance, fermented soybean straw, bacterium-enzyme synergy, rumen microorganisms