Abstract: The purpose of this study was to investigate the effect of steam explosion pretreatments, compound bacteria fermentation and their combined treatment on the degradation of fiber in Caragana. In flowering stage (April), fructicative stage (July) and dormancy stage (November), the whole plant of Caragana was collected and its general nutrients were determined. According to the research content, the experiment was divided into 3 parts: 1)Degradation of fiber components in Caragana powder was studied under 3 different steam explosion pressures (0.8、1.1 and 1.4 MPa). 2)The effect of compound bacteria fermentation on the degradation of Caragana powder fiber component was determined. 3) The effect of steam explosion + compound bacteria fermentation on the degradation of Caragana powder fiber component was studied. The 3 growth periods of Caragana powder in each experiment were regarded as fixed factors. All treatments were compared with untreated Caragana powder in the same period, and each treatment was repeated 3 times. The neutral detergent fiber, acid detergent fiber, lignin, hemicellulose and cellulose, and the activity of carboxymethyl cellulase and xylanase were detected in each treatment. The results showed that: 1) According to the nutrient component, Caragana had the highest feeding value at the fructicative stage. 2) Compared with the control group, the content of neutral detergent fiber, acid detergent fiber, lignin (only in flowering stage) and cellulose increased first and then decreased (P<0.05), Hemicellulose decreased linearly (P<0.01), and the content of neutral detergent solute decreased first and then increased (P<0.05) as steam explosion pressureincreasedat flowering and fructicative stage. 3) Compared with the same period before fermentation, the content of neutral detergent fiber (P<0.01), acid detergent fiber (P<0.01) and cellulose (P<0.01) decreased significantly and neutral detergent solute (P<0.01) increased significantly after fermentation. The hemicellulose decreased significantly at flowering and dormancy stage (P<0.01). 4) After steam explosion pretreatment and fermentation, the content of neutral detergent fiber (P<0.001), acid detergent fiber (P<0.05) and hemicellulose (P<0.001) decreased significantly, the content of cellulose decreased significantly at flowering and fructicative stage (P<0.01), and the content of neutral detergent solute (P<0.001) increased significantly with the increase of steam explosion pressure at the flowering stage and dormancy stage, and the content of lignin (P<0.05) decreased first and then increased at flowering and fructicative stage, and decreased significantly at dormancy stage (P<0.01) with the increase of steam explosion pressure, compared with the same period without steam explosion pretreatment. 5) After steam explosion pretreatment and fermentation, carboxymethyl cellulase activity (P<0.001) first decreased and then increased at the flowering anddormancy stage, while carboxymethyl cellulase activity (P<0.001) significantly increased in the fructicative stage with the increase of steam explosion pressure; the xylanase activity (P<0.001) increased linearly with the increase of steam explosion pressure in the three periods. The results indicated that the fiber content of Caragana at different harvest time could be significantly reduced by steam explosion, compound bacteria and their combined treatment, among which the effect of combined treatment was the best. This study provides scientific basis and data support for the effective evaluation of the nutritional value of Caragana and its application in animal husbandry.

Key words: Caragana, steam explosion, fermentation of complex bacteria, fiber degradation