| Based on a certain ratio of several kinds of straw to perennial ryegrass,legumes such as alfalfa and common vetch were mixed in different proportions with straw and perennial ryegrass in order to examine the effects of mixed silage on nutritive value,microorganisms,crude protein and in vitro digestibility without using any additives.Agricultural byproducts straw used in this study included hulless barley straw,wheat straw,oat straw and rape straw,perennial ryegrass and two legumes(alfalfa,common vetch)were mixed in different proportions with straw.According to previous study on the optimum ratios of several kinds of straw to perennial ryegrass,the designed ratios of straw to perennial ryegrass were all set to 40%:60%.Straw and grass-legume mixed silage containing 0(control),10%,20%,30%of legume(alfalfa,common vetch)were combined from chopped materials.Silos were opened after 45 days,the mixed silage were expected to improve the fermentation quality,improve the protein content and balance the nutrition value.This study were divided into four sections:Experiment 1:Fermentation quality of mixed silage of hulless barley straw,perennial ryegrass and legumes.The results were as follow:The pH value of control and all treatments were higher than 4.2,an obvious(P<0.05)pH increase was detected in all alfalfa and common vetch treatments.Alfalfa treatments had higher(P<0.05)lactic acid concentration than control while no changes were found in dry matter content.Common vetch treatments had greater(P<0.05)dry matter content than control,changes in the water soluble carbohydrate content were same as the trend detected in dry matter content.Ammonia nitrogen/total nitrogen content decreased,especially(P<0.05)in common vetch treatments.A distinct increase was showed in lactic acid bacteria and aerobic bacteria population of alfalfa treatments while no significantly changes in common vetch treatments.In-vitro digestibility showed no differences.Considering of fermentation quality and nutritional quality,30%alfalfa were recommended for mixed silage.Experiment 2:Fermentation quality of mixed silage of wheat straw,perennial ryegrass and legumes.Differences in pH value between control and alfalfa treatments were not found,while a distinct pH increase(P<0.05)with higher proportions of legumes was showed in common vetch treatments.Lactic acid concentration increased in both alfalfa and common vetch treatments.With higher proportions of alfalfa and common vetch added in mixed silage,the dry matter contents decreased.An obvious water soluble carbohydrate decrease was showed in all treatments,average water soluble carbohydrate content was bellow 20 g/kg DM.There was a distinct(P<0.05)increase in acetic acid concentration and the ratio of lactic acid to acetic acid was about 2 which suggests a dominant hetero-fermentation during the ensilage period.Butyric acid concentration was decreased in alfalfa treatments,compared with control,there was an increase in total volatile fatty acids concentration in both alfalfa and common vetch treatments.The crude protein content increased a lot(P<0.05),compared with common vetch treatments and control,ammonia nitrogen/total nitrogen increased a lot in alfalfa treatments.No obvious changes were found in in-vitro digestibility.Without enough fermentation substrates and a proper moisture content,legumes were not recommended for mixed silage.Experiment 3:Fermentation quality of mixed silage of oat straw,perennial ryegrass and legumes.Compared with control,either alfalfa treatments or common vetch treatments had obvious changes in pH value,though lactic acid concentration increased in all treatments.The dry matter content decreased,in addition,dry matter content in all treatments and control were bellow 300 g/kg FW.There was a great(P<0.05)decrease in water soluble carbohydrate in all treatments,the acetic acid content decreased a lot(P<0.05)in alfalfa treatments,while no such trend was detected in common vetch.Lactic acid/acetic acid seemed to increase in alfalfa and common vetch treatments,the concentration of butyric acid was bellow 10 g/kg DM.An obvious increase was found in crude protein content and NDF,ammonia nitrogen/total nitrogen was greatly(P<0.05)dropped,while no obvious changes in in-vitro digestibility.30%alfalfa were suggested for mixed silage with oat straw and ryegrass.Experiment 4:Fermentation quality of mixed silage of rape straw,perennial ryegrass and legumes.The pH value in alfalfa treatments and common vetch treatments was greatly(P<0.05)reduced,and the lactic acid concentration increased a lot(P<0.05),dry matter content increased with the increasing proportion of legumes.The water soluble carbohydrate content decreased greatly(P<0.05)with the increasing proportion of alfalfa,while not obvious in common vetch treatments.Compared with control,the acetic acid concentration increased in all treatments,and the ratio of lactic acid/acetic acid increased,too.The highest ratio of lactic acid/acetic acid reached to 5.09.Crude protein content and ammonia nitrogen/total nitrogen increased greatly(P<0.05),and NDF content also increased by a large amount,while no obvious changes found in butyric acid,total volatile fatty acids concentration and in-vitro digestibility.Considering of fermentation quality and nutritional quality,30%alfalfa were recommended for mixed silage. |
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