Nutritional Estimation Of Corn Stover And Its Application As Substrate For Fermentation Feed

In this study, a comparative experiment on chemical compositions and ruminal degradability of different corn stover fractions was carried out and determined the different corn stover fractions’ nutritional value. After that, through mixing corn steep liquor into corn stover and rind-removing corn stover during micro-storage, the effect of corn steep liquor with different proportion on the indicators of micro-storage’s fermentation quality was investigated to define the suitable dosage for corn steep liquor in micro-storage of corn stover and rind-removing corn stover. And then, through studying on the effect of the culture medium inoculated with Saccharomyces cerevisiae on sulfites we also determined the suitable amount of the inoculum for Saccharomyces cerevisiae in corn steep liquor and the effective the inhibition of lactic LAB with sulfites and solved the problem of negative influence on poultry if corn steep liquor were utilized as feed. Finally, we produced corn steep liquor undergone biological or chemical-biological treatment, whose effect on the fermentation of micro-storage of corn stover with or without rind was tested and verified, including major quality, nutritional composition, and aerobic stability; and afterwards, we determined feed fermentation technology of high protein corn stover. These experiments have provided scientific reference data forfully utilization of different fractions of corn stover, and solved the the key problem of its low protein level, if it were used as feed, through which could turn corn steep liquor and corn stover from waste into treasure, and therefore it is of great significance for improving the efficiency of utilizing corn stover resources, reducing environmental pollution.Experiment1. The assessment of the nutritive values of different fractions of corn stoverThe nutritional compositions, and ruminal degradability of dry matter (DM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) from seven morphological fractions of corn stover, which were leaf blade, leaf sheath, stem rind, stem pith, stem node, ear husk, and corn tassel, were evaluated by general laboratory assays and nylon bag technique. The results show that, leaf blade had the highest crude protein (CP) content (p<0.05) and the lowest NDF and ADF contents (p<0.05) compared with other morphological fractions of corn stover, whereas stem rind had the highest ADF and acid detergent lignin (ADL) contents (p<0.05). Ear husk had the highest NDF content and the lowest ADL content (p<0.05). The effective degradability of DM, NDF, and ADF in rumen was significantly higher (p<0.05) in leaf blade, stem pith, and ear husk than in other fractions of corn stover.Experiment2. The effect of corn steep liquor on fermentation quality of corn stover This experiment was of single factor design, which investigated the effect of different proportions (0%,15%,20%,25%and30%) on the dynamic changes of the numbers of lactic acid bacteria (LAB), lactic acid (LA), acetic acid (AA), LA/AA, pH value, crude protein (CP), ammoniacal nitrogen (AN) and the ratio of ammoniacal nitrogen to total nitrogen (AN/TN) in micro-storage of corn stover (Sampling on the day0.5,3,7,17,23,35,50and60in micro-storage). The results indicate that, the CP and LA content increased gradually (p<0.05), whereas the pH of raw materials decreased gradually (p<0.05). The results also indicate that, the range of dynamic change of LA and AA decreased gradually, the numbers of LAB decreased systematically (p<0.05) and there was obviously decreasing tendency in AN and AN/TN, with the rising proportion of corn steep liquor.Experiment3. The effect of corn steep liquor on fermentation quality of rind-removing corn stoverThis experiment was of single factor design, which investigated the effect of adding corn steep liquor with different proportions on dynamic changes of the numbers of LAB, LA, AA, LA/AA, pH value, CP, AN and AN/TN in micro-storage of rind-removing corn stover (Sampling the same as Experiment2). The results demonstrate that, at the begining of micro-storage, CP and LA content in test group increased with rising proportion of corn steep liquor. During fermentation of rind-removing corn stover micro-storage, with the increment of corn steep liquor proportion, the rise in numbers of LAB decreased, whereas no distinct changes were observed in AA content. The AA content of control group were significantly higher (p<0.05) than that of the test groups at3-60d. The pH in test groups exhibited increased at first and then decreased; and the time point of its decrement was postponed due to the increment of corn steep liquor proportion. AN and AN/TN in treatment1and treatment2remained steady after an increment of23d, and the AN and AN/TN in treatment3and treatment4remained steady after3d.Experiment4. The inhibition of LAB with sulfites and the effect of Saccharomyces cerevisiae on sulfitesNa2SO3was added into MRS agars to reach a concentration of0.35%, whose pH agar were adjusted to3.5,4.0,4.5and5.0by lactic acid to study the inhibition of LAB with sulfites at different pH values. Na2SO3was added into potato dextrose agars to reach a concentration of0.35%, whose pH were adjusted to3.5,4.0and4.5by lactic acid, and then inoculated with Saccharomyces cerevisiae of104、105and106to study the effect of pH and inoculum dose (Saccharomyces cerevisiae) on sulfites. The results indicate that, at relatively low pH (4.0or3.5), sulfites had strong inhibit effect on LAB, and the viable count of bacteria was0, with the increasing of pH, the inhibit effect had tendency of weakening. The results also demonstrate that, saccharomyces cerevisiae can utilize part of sulfites. Desulfurization in this experiment reached over50%, however, no significant effects on Saccharomyces cerevisiae desulfurization at different pH values (3.5-4.5) and with different inoculum doses.Experiment5. The effect of combined treatment of corn steep liquor on fermentation quality of corn stoverTo study the effect of combined treatment of corn steep liquor on fermentation quality of corn stover,20%corn steep liquor and20%corn steep liquor inoculated with Saccharomyces cerevisiae were mixed with corn stover separately as control groups (A2K and N2K). Corn steep liquor containing1.5%Ca(OH)2and with Saccharomyces cerevisiae inoculation were mix with corn stover in proportion of15%,20%,25%and30%as treatment groups (M1, M2, M3and M4). The results demonstrate that, corn steep liquor treated with Saccharomyces cerevisiae alone or combined treatment both impair the inhibitory function of sulfites on LAB in corn steep liquor. However, the number of LAB in M1, M2, M3and M4were higher than N2K at most time points. The increasing speed of LA content in0.5～17d of micro-storage were M4>M3>M2>M1>NK2>AK2(p<0.001), LA content of all samples in test group expect for M4reached their peak value significantly earlier than A2K and N2K. AA content of A2K changed less during the whole micro-storage process, and were significantly lower than N2K and test groups (p<0.05). The dynamic change of AA content in M1, M2, M3and M4showed the tendency of rising at first and then reducing, and the AA content of them were significantly higher than N2K at most time points (p<0.05). In the early period of in micro-storage, the pH of A2K showed a gradually increasing tendency of, the pH of N2K and test group shown the tendency of decreasing. However, the drop of pH in test group was significantly bigger than the control group. AN and AN/TN in A2K were higher than in N2K and test groups during micro-storage.Experiment6. The effect of combined treatment of corn steep liquor on fermentation quality of rind-removing corn stoverTo study the effect of combined treatment of corn steep liquor on the main fermentation quality of rind-removing corn stover in micro-storage,20%corn steep liquor and20%corn steep liquor inoculated with Saccharomyces cerevisiae were mixed with corn stover separately as control groups (C2K and Y2K). Corn steep liquor containing1.5%Ca(OH)2and inoculated with Saccharomyces cerevisiae mixed with corn stover in proportion of15%,20%,25%and30%as treatment groups (U1, U2, U3and U4). The results demonstrate that, during micro-storage, the number of LAB in C2K maintained at103-105which was significantly lower than Y2K and test group (p<0.05). In the later stage of micro-storage, that is after35～60d, the number of LAB in Y2K was significantly lower than that in test group. The LA and AA content in C2K were significantly lower than that in Y2K and test group at most time points, and the LA and AA content in Y2K was significantly lower than that in test group. AN and AN/TN in Y2K and test groups were equally lower than that in C2K during micro-storage.Experiment7. The effect of corn steep liquor with different treatments on the aerobic stability and quality of micro-storage of corn stover fermentationThis experiment was of2×2×4design, in which corn stover (or rind corn stover) was inoculated with Saccharomyces cerevisiae [or Saccharomyces cerevisiae and Ca(OH)2together] in corn steep of different concentrations (15%,20%,25%and30%) to study the effect of corn steep liquor after different treatment on the major nutritional compositions and aerobic stability of micro-storage of straw. The results indicate that, the contents of CP, NDF and ADL after micro-storage fermentation were higher than before. Its aerobic stability were gradually decreasing with the increasing proportion of corn steep liquor, the aerobic stability of rind-removing corn stover was decreased after micro-storage. Regarding to corn steep liquor treated with both Ca(OH)2and Saccharomyces cerevisiae, the aerobic stability of it was significantly superior than the group which was only inoculated against Saccharomyces cerevisiae. The pH value of the combined treatments group has a low raise, and loss of dry matter was less than other groups.Based on the results above, conclusions of this study are as follows:1. Chemical compositions in different morphological fractions of corn stover are distinctly varied. The nutritive values of leaf, ear husk and stem pith are superior to that of other fractions according to the dynamic evaluation of ruminal degradability and effective degradability of different morphological fractions of corn stover.2. The protein level in micro-storage can be significantly elevated by mixing corn steep liquor as with corn stover and rind-removing corn stover. However, growth and reproduction of LAB are inhibited with the increment of corn steep liquor proportion; and the pH decreases slowly, which weighted against the fermentation of corn stover feed. Comprehensive analysis of the results demonstrate that, the best proportion of corn steep liquor added in micro-storage of corn stover and rind-removing corn stover are15～20%and15%, respectively.3. Corn steep liquor with Saccharomyces cerevisiae treatment alone or with combined treatment can relief the inhibit effect of sulfite to LAB in corn steep liquor during in micro-storage, and can facilitate the biological metabolism of LAB, through which the content of LA and AA are significantly increased in the initial stage of fermentation, and the AN and AN/TN significantly decreased during in micro-storage. Corn steep liquor treated with Ca(OH)2and Saccharomyces cerevisiae have more significant advantage towards in micro-storage.4. Protein level be improved through utilizing corn steep liquor mixed with corn stover rind-remongving corn stover in micro-storage. However, the aerobic stability decreases with the increasing of the proportion of corn steep liquor. Aerobic stability of micro-storage utilizing corn steep liquor treated with Ca(OH)2and Saccharomyces cerevisiae is superior to other group with single treatment. Lignin content of corn stover significantly decreases after stem rind removal, however, the aerobic stability of which decreases comparing with corn stover during micro-storage.