| Straw is a potential non-competitive resource.It has the characteristics of large quantities, widely distributed and many kinds. At present, because of the shortages of global resources and food, the development of straw animal husbandry has great ecological and economic value.The aim of this study was to isolate cellulase-producing microorganisms from bovine rumen, and to maximize the development and use of straw resources to solve the problem for livestock food competition, and promote the development of animal husbandry . Four experiments were included in this study.Experiment 1: The microorganism from bovine rumen was first screened in selective culture medium for cellulase detection, and then cultured in cellulose congo red medium and corn straw medium. One superior cellulose decomposing strain (No.3) was isolated from bovine rumen. The CMCase and filter paper cellulase activity were 6.01 U.g-1 and 1.15 U.g-1, respectively. The contents of reducing sugar and soluble protein in the corn straw fermented with No.3 were increased. The strain was identified as Aspergillus oryzae (A. oryzae)by morphological and 26S rDNA technique.Experiment 2: Aspergillus oryzae isolated from bovine rumen was used for solid fermentation of corn straw to determine cellulase characteristics and fermentation results. The results showed that the optimum pH and temperature of cellulase were 5.5～6.0 and 50℃, respectively. The stability of pH and temperature of cellulase were 4.0～6.0 and 30℃～50℃, respectively. Cellulase activity was significantly improved by CaCl2 and MnSO4, and decreased by FeSO4 and NaCl. KH2PO4, MgSO4, ZnCl2, CoCl2 had strict concentration range, and had different function on different cellulase activity. Compared with the control, the contents of reducing sugar and soluble protein in the corn straw fermented with A. oryzae were increased by 123.53% and 48.98% (P<0.05), and the degradation rates of cellulose and hemi-cellulose were 25.01% and 45.99%(P<0.05), respectively. The results indicated that A. oryzae had high application value, and it would be used as a potential strain for straw utilization.Experiment 3: In order to determine the optimum fermentation conditions for A. oryzae, the effect of fermentation of corn stalks in different conditions were studied. The results show that the optimum amount of compound feed, inoculation volume, ratio between material and water, particle size , fermentation time were 10%(P>0.05), 1%(P>0.05), 1:1.5(P>0.05), 1~2cm(P<0.05)and 3 d(P<0.05), respectively. Experiment 4:Twenty-five AA broilers aged of six weeks were randomly assigned to five groups to study the effects of corn straw fermented with A. oryzae instead of corn on digestive enzyme activities and gut microbes of broilers. The control group was basal diet, and the negative group was added 8% unfermented corn straw instead of corn. The other three groups were added 4%, 8 % and 12 % fermented corn straw instead of corn, respectively. The results showed that adding a certain amount of fermented corn stalk in diet could improve the digestion and absorption of crude protein, crude fat, calcium, neutral detergent fiber and acid detergent fiber, except for phosphorus.Three diets containing fermented corn straw could increase lactic acid bacteria and Aspergillius oryzae amount (P< 0.05), and decrease E.coli amount in ileum and cecum of broilers (P<0.05), compared with the control and negative groups. The intestinal digestive enzyme activities such as cellulase, protease and amylase were significantly increased (P<0.05) by the fermented corn straw. The optimal level of the fermented corn straw instead of corn was 8%.
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