| This dissertation mainly studies the effects of compound fermentation of rice straw by Aspergillus niger and Candida utilis on its quality,and explores the optimal fermentation conditions for compound bacteria to ferment rice straw.After that,the in vitro gas production method is used to study the separate fermentation and production of rice straw by Aspergillus niger.Candida utilis singly fermentation and rice straws after the compound fermentation of Aspergillus niger and Candida utilis affect the in vitro fermentation of the rumen of black-and-white dairy cows.Comprehensive evaluation of the nutritional value of fermented rice straw provides technical and theoretical support for rice straw in animal husbandry production.Experiment 1: The influence of different fermentation conditions on the NDF and ADF content of rice straw and response surface optimizationThe experiment uses rice straw as the raw material,and conducts the research of five factor experiments.Different temperature(34 ℃,32 ℃,30℃,28℃),time(5 d,4 d,3 d,2 d,1 d),water content(70%,60%,50%,40%,30%),mixed bacteria Inoculation amount(10%,8%,6%,4%,2%),inoculation ratio(Aspergillus niger: Candida utilis 1:1,1:2,1:3,2:1,3:1)The effect on the content of NDF and ADF in rice straw,3 replicates for each treatment.First carry out single factor experiment,and then use response surface to make corresponding optimization on this basis to find the best fermentation environment.The results showed that:(1)Fermentation temperature: 30℃ group had the lowest NDF and ADF content,and was significantly lower than other treatment groups(P<0.05);(2)Fermentation time: 3d group NDF,ADF content was the lowest,of which NDF content was compared with other treatment groups In comparison,the difference was significant(P<0.05),the content of ADF was significantly lower than that of the 1d group(P<0.05),and it was not significantly different from the 2d,4d,and 5d groups(P>0.05);(3)The fermentation water content:50% The NDF content of the group was significantly lower than that of the 30%,40%,and 70%water content treatment group(P<0.05)and the water content of 60% was not significantly different(P>0.05);ADF and water content were 30%,70% The difference between the two groups was significant(P<0.05),but not significantly different from the water content of 40% and 60%(P>0.05);(4)The amount of mixed bacteria inoculation: The NDF content in the 6% group was significantly lower than in the other test groups(P<0.05)),the ADF content was significantly lower than the inoculation amount of 2% and 10% treatment group(P<0.05),and the inoculation amount of 4% and 8% were not significantly different(P>0.05);(5)Aspergillus niger and Candida utilis The content of NDF and ADF in the 1:1 group was significantly lower than that in the 2:1and 3:1 groups(P<0.05),and the difference was not significant when the Aspergillus niger: prion ratio was 1:2 and 1:3(P>0.05);(6)Therefore,when the fermentation temperature is 30℃,the fermentation time is 3d,the water content is 50%,the mixed bacteria inoculation amount is 6%,and the mixed bacteria inoculation ratio is 1:1,the minimum NDF and ADF content of rice straw is 64.00% and 42.97.%,significantly lower than the NDF and ADF content of unfermented rice straw(P<0.05).Test 2: The effect of rice straw fermented by mixed bacteria on in vitro rumen fermentationRice straw fermented by Aspergillus niger,rice straw fermented by Candida utilis and rice straw fermented by mixed bacteria(Aspergillus niger and Candida utilis 1:1)are used as fermentation substrates,and each process is repeated for 3,Take the rumen fluid of healthy Holstein cows and conduct the in vitro fermentation test in the rumen.During the experiment,the gas production was recorded at 2 hours,4 hours,8 hours,12 hours,24 hours,36 hours,and 48 hours,and the fermentation broth of each group was collected at 24 hours and 48 hours,respectively.After the test,the rumen fermentation index was measured.The test results showed that the gas production of the Aspergillus niger group,the Candida utilis group and the mixed bacteria treatment group in the rice straw was significantly higher than that of the control group(P<0.05).At 24 h,the DMD content of the three treatment groups was significant Higher than the control group(P<0.05),the highest is that the mixed bacteria group has14.05% more than the control group,which is 52.17%,and the second highest is the group with Aspergillus niger alone,which has a DMD of 46.09%,which is 7.97 higher than the control group.At 48 hours of fermentation,the DMD of each treatment group was significantly different from that of the control raw material group(P<0.05),which increased by 5.97%,5.23%,and 9.17%,respectively,compared with the control group.The DMD of the mixed bacteria group was the highest;p H and NH3-N changed within the normal range at two time points of 24 h and 48 h.At the same time,the MCP concentration of the mixed bacteria at these two time points is also the highest;the concentrations of AA,PA,BA and TVFA with the addition of Aspergillus niger,the addition of Candida utilis and the addition of the mixed bacteria are all higher than those of the control group and the difference is significant(P<0.05).in Conclusion:(1)the optimum conditions of Rice Straw fermentation by mixed bacteria were: temperature30 °C,time 3d,water content 50%,inoculation ratio of aspergillus Niger and Candida Utilis 1:1,inoculation quantity 6%.(2)the fermentation parameters of rice straw were optimized by response surface methodology(RSM).Under these conditions(temperature: 30 °C,TIME: 3D,water content: 50%,mixed bacteria inoculation: 6%),the highest degradation rates of NDF and ADF of fermented rice straw were 64.31% and 43.23%,respectively.(3)the results of in vitro fermentation of rice straw by mixed bacteria showed that the rice straw with mixed bacteria had the best fermentation effect. |
