Study On Harvesting Model And Quality Control Mechanism Of Native Pasture

In order to preserve the nutritional quality of native pasture effectively,clarify the mechanism of nutrient loss in pasture,changing the traditional grazing mode,improving the utilization rate of native pasture,and ensure that livestock can have nutritional grass.The native pasture in typical steppe was used in this study,to clarify the nutritive level of pasture systematically,the nutritive substance of native pasture was studied.Four harvest conditions which affecting the nutrient quality of pasture were selected,including the harvest time,stubble height,rainfall and mowing times.Through the orthogonal experimental design with four factors and three levels(34),the optimal harvest conditions of native pasture were determined by combining the analysis of nutrient quality,digestibility and reviving rate under different harvest conditions of typical grassland in Bahrain town.The constructive species(Stipa grandis)and the dominant species(Leymus chinensis)were regarded as raw materials,and the metabolomics technology was used to analyze the different expression of metabolites in native pasture at different harvest time,and to clarify the mechanism of quality in native pasture at different harvest time.At the same time,in order to study the compensatory growth rule of native pasture,the effects of different mowing techniques on relative growth height,height and density of native pasture were studied.On the basis of the determination of five main pasture species in typical grassland,the heterogeneity of volatile matter of pasture in different harvest periods was studied which would provide new directions and ideas for the future harvesting and utilization of pasture.In the whole process of research,the following results were obtained through the sample line survey,orthogonal test design and metabolomics research,combined with data analysis methods such as clustering method,range method,one-way ANOVA,optimal generating sequence and fuzzy evaluation:(1)There were 33 species of native pasture in the typical grassland of Bahrain town,including 20 species of pasture,which have higher fiber,while 13 species lower.Based on the comprehensive evaluation of dry matter(DM),crude protein(CP),crude fat(EE),NDF,ADF and water soluble sugar(WSC),the optimal harvest time of Stipa grandis,Leymus chinensis and native pasture were determined on August 20.(2)Compared to the metabonomics results in proper harvest time(August 20)and the traditional harvest time(September 20),we can know that the The expression levels of phenylacetamide,lysine,alanine,aspartic acid,glutamic acid,purine,pyrimidine and other metabolites related to protein synthesis were significantly down-regulated if the harvest time delayed,and it caused CP reduced;while the expression levels of iso-glutamine,phenylalanine,1-glutamic acid and carbohydrate were significantly up-regulated,and it caused fiber raised.This not only revealed the internal mechanism of CP reduced and fiber raised for grass harvest delayed,but also further verified the importance of grass harvest timely.(3)The cutting frequency had significant influence on the relative growth height,coverage,density,biomass and returning rate of forage in the current year and the following year(P<0.05).With the increase of cutting frequency of native pasture,the compensatory growth ability of grass after cutting will be reduced,and the relative growth height,coverage,density,biomass and the winter survival rate will be decreased.Therefore,the cutting mode of cutting twice a year and three times in two years is not suitable for the typical grassland of Bahrain town.Considering the ecological and economic factors,the most appropriate mowing frequency is once a year.(4)The volatiles of Stipa grandis,Leymus chinensis,Lespedeza davurica,Cleistogenes chinensis,Agropyron cristatum contained alkenes,ketones,lipids,alcohols and alkanes.The other volatiles were Aldehydes,phenols,benzenes,naphthalines and acids,among which the alkenes are the most abundant.The delay of harvest led to the increase of phenols and benzenes,which affected the palatability of the grass,and reduced the utilization rate of the grass.(5)Comprehensive the results,the proper harvest model was the harvesting time was about August 20,the stubble height was 5 cm,and the cutting frequency was once a year.This model can not only gained high-quality grass which has high content of CP,soluble sugar,and lower fiber,but also have no negative effect on native pasture ecology.