| In this experiment,two white rot fungi and their mixed strains were used to degrade lignocellulose,and the effects of two white rot fungi and their combined fermentation on the nutritional value of soybean straw,sweet potato vine and peanut straw were investigated.The effects of pretreatment of single and mixed white rot fungi on rumen degradation rate and in vitro gas fermentation of three kinds of straw were compared by nylon bag method and in vitro gas production method.The test results are as follows:Experiment 1:Effect of white rot fungi on fermentation of three kinds of straw for 30 days.The results showed that:（1）White rot fungi fermentation can effectively degrade three kinds of straw surface structure,and the straw surface structure of Phanerochaete Chrysosporium（Pc）treatment showed more holes.The mycelia of Pleurotus Ostreatus（Po）covered the surface of straw,and the fiber structure of straw was broken.（2）The degradation rates of dry matter,cellulose and hemicellulose of peanut straw,sweet potato vine and soybean straw treated by Po were significantly lower than those treated by Pc（P<0.01）.The effect of single white rot fungi on lignin degradation of peanut straw,sweet potato vine and soybean straw was better than that of mixed fermentation.（3）The degradation rate of soybean straw lignin（ADL）in Po and Pc treatments（36.15%and 34.43%）was significantly higher than that in PoPc treatment（27.27%）（P<0.01）.The degradation rates of ADL in Po and Pc treatments（21.84%,23.06%）were significantly higher than those in PoPc treatment（17.97%）（P<0.01）.However,the ADL degradation rate of peanut straw treated with Po（32.04%）was significantly lower than that treated with Pc and PoPc（63.60%and 61.89%）.The dry matter degradation rate of sweet potato vine treated with Po（21.84%）was higher than that of soybean straw（2.90%）and peanut straw（4.39%）.（4）According to the Selective Value（SV）of different white rot fungi to cellulose and lignin degradation,the SV value of Po to soybean straw was the highest,which was 5.70.Po,Pc and mixed bacteria could improve the NDS of soybean straw after fermentation.The effect of Po on soybean straw was better than that of sweet potato vine and peanut straw.Experiment 2:Effects of white rot fungi treatment on rumen fermentation performance and main bacteria of three kinds of straw in vitro.The results show:（1）The 48 h total gas production and total volatile acid（TVFA）concentration of soybean straw,sweet potato vine and peanut straw treated by white rot fungus were significantly decreased（P<0.01）,and the 48 h total gas production of pleulopleulosus squarosa（Po）treatment was significantly higher than that of Pc and PoPc treatments（P<0.05）.There was no significant difference in 48 h gas production between Pc and PoPc.The total gas production of in vitro fermentation of Pc straw was significantly lower than that of untreated straw（P<0.01）.（2）The pH value of soybean straw fermentation broth treated by two kinds of white rot fungi and their combination was significantly higher than that of control group（P<0.01）.The pH value of 48 h fermentation broth of sweet potato vine and peanut straw treated by Pc and PoPc was significantly higher than that of control group（P<0.01）.There was no significant difference in the 24 h ammonianitrogen（NH3-N）concentration of soybean straw treated by white rot fungi among all groups（P=0.07）,and the 24 h NH3-N concentration of sweet potato vine and peanut straw treated by Pc was significantly higher than that of sterilization group（P<0.01）.（3）Ruminococcus albus and Ruminococcus flavanum in 24 h fermentation broth of sweet potato vine and peanut straw treated with Po were significantly higher than those in other groups（P<0.01）;The contents of Prevotella in fermentation broth were significantly lower than those in sterilized raw material group（P<0.01）.There was no significant difference between in vitro rumen methanobacteria and peanut straw treated by white rot fungi for 24 h.The relative amount of methanogens in soybean straw and sweet potato vine treated with Po for 24 h was significantly lower than that in sterilization group（P<0.01）.Experiment 3:The effects of white rot fungi on rumen degradation test and fiber quality of three kinds of straw.The results showed that after 30 days of Pc treatment,the DM rapidly degraded part of three kinds of straw was higher than that of other treatment groups（P<0.01）.The degradation rate of nutritional components of straw treated with PoPc was basically consistent with that of Pc（P>0.05）.（2）The effective degradation rates of DM of three kinds of straw treated by Po were lower than those of raw material group（P<0.01）.（3）The rumen degradation rates of nutrients in raw sweet potato vine and peanut straw were higher than those in soybean straw.After white rot fungus treatment,the rumen degradation rates of DM,NDF and ADF of straw were significantly reduced in raw material group,but the effective degradation rates of CP and DM in soybean straw treated by Pc were significantly higher than those in all treatment groups（P<0.01）.（4）The fermentable fiber index（FFI）of raw sweet potato vine was the highest,and the FFI of PoPc treated peanut straw was the lowest.The fermentable fiber index of Po treatment was higher than that of Pc and PoPc treatment after white rot fungi treatment（P<0.05）.The digestible NDF（dNDF）of sterilized sweet potato vines and Po treated sweet potato vines was the highest,and there was no significant difference between them（P>0.05）.The RFV of Pc treated peanut seedlings was the highest,while that of sterilized soybean straw was the lowest.In conclusion,Po has high Selective Value（SV）for lignin degradation of soybean straw,sweet potato vine and peanut straw,and soybean straw has the highest SV.Soybean straw treated with Po could improve the rumen fermentability,decrease the expression of methanogens and increase the expression of fibre-degrading bacteria by changing its nutrient composition.After 30 days of Po treatment,the effective degradation rates of DM,NDF and ADF were all lower than those of raw material group.Therefore,the pretreatment of soybean straw with the lowest nutritional value of Po has more application potential in animal production. |
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