Effects Of Two Functional Native Grasses On Digestion And Metabolism Of Grazing Sheep In Sown Grassland

Functional native grasses have important regulatory effects on the digestive metabolism and productivity of livestock because they contain secondary metabolites that are generally less frequently taken by grazing livestock,mistakenly consumed in small amounts,or taken only in specific seasons or specific organs.Capparis spinosa L.and Cynanchum chinense R.Br.are common functional native grasses in inland arid zones,and their effects on the digestive metabolism and environmental footprint of grazing livestock are unclear.So,in the Hexi oasis,this thesis investigated the effects of Capparis spinosa L.and Cynanchum chinense R.Br.on digestive metabolism,enteric CH₄ emission and immune function of sheep which grazing in mixed alfalfa/tall fescue grassland.The main results were as follows.1.Effects of adding C.spinosa on the digestion and metabolism of sheepTwenty-four healthy male lambs of similar body weight and 6 months of age were randomly divided into four groups（n=6）,and supplemented with 0（CON group）,0.83（LA group）,1.67（MA group）and 3.33 g/kg BW（HA group）of C.spinosa,respectively,and digestion and metabolism,enteric CH₄ emissions were measured in the metabolic chamber.（1）Effects on digestion and metabolism:comparing with CON,the per unit metabolic body weight of dry matter intake(DMI/BW^0.75)and dry matter digestibility（DMD）in the MA were 18.20%（P=0.005）and 15.62%（P<0.001）higher,respectively.Moreover,the per unit metabolic body weight of nitrogen intake(NI/BW^0.75),nitrogen retained(RN/BW^0.75)and nitrogen retained/nitrogen intake（RN/NI）in the MA were 18.26%（P<0.001）,57.14%（P<0.001）and 30.99%（P<0.001）higher than those in the CON,respectively.（2）Effects on enteric CH₄ emission:ruminal acetate and valerate acid molar ratios in the MA were 6.53%（P=0.040）lower and 27.21%（P=0.010）higher than those in CON,respectively.Daily enteric CH₄ emission in the LA was 47.50%（P=0.025）higher than that in the CON.（3）Effects on serum parameters:the concentrations of serum superoxide dismutase（SOD）and glutathione peroxidase（GSH-Px）showed an upward concave parabolic trend with increasing levels of C.spinosa,and both were the highest in the HA,and they were 17.85%and 8.65%higher than that in the CON,respectively.Malondialdehyde（MDA）concentrations in the MA and HA reduced by 9.93%and1.25%than that in the CON,respectively.（4）Effects on rumen microorganisms:the dominant phylum were Bacteroidetes and Firmicutes,the relative abundance of Spirochaetae in the MA group of sheep was4.16-fold higher（P=0.008）and Christensenellaceae＿R＿7＿group was 44.96%lower（P=0.025）than that of the CON group.At the fungal community level,the relative abundance of Ascomycota was 1.25-fold（P=0.001）higher in the MA group of sheep compared to the CON group.2.Effects adding C.chinense on the digestion and metabolism of sheepTwenty-four healthy male lambs of similar body weight and 6 months of age were randomly divided into four groups（n=6）,and supplemented with 0%（CON）,10%（LA）,15%（MA）and 20%（HA）of C.chinense,respectively,and digestion and metabolism,enteric CH₄ emissions were measured in the metabolic chamber.（1）Effects on grazing behavior:comparing with the CON,sheep in the MA showed a 44.96%（P=0.015）decrease,17.18%（P=0.017）and 37.63%（P=0.022）increase in the number of mouthfuls taken per step,time to chew a single food mass and time between two food masses in alfalfa/tall fescue mixed grass,respectively.（2）Effects on digestion and metabolism:comparing with CON,DMD,CPD and ADFD were 23.34%（P=0.020）,14.64%（P=0.039）and 16.70%（P=0.031）higher in the MA of sheep,respectively.（3）Effects on enteric CH₄ emissions:comparing with CON,the per unit dry matter intake of CH₄ emission（CH₄/DMI）and per unit organic matter intake of CH₄emission（CH₄/OMI）of sheep in the MA showed a downward parabolic trend as the proportion of C.chinense added increased,reaching a minimum,with a 16.36%and18.01%reduction,respectively.（4）Effects on serum indices:comparing with CON,the concentrations of SOD and GSH-Px in the LA group increased by 5.81%（P>0.05）and 12.17%（P=0.001）,while the MDA concentrations decreased by 25.16%and 22.57%（P=0.002）compared to the MA and HA groups,respectively,and the albumin（ALB）in the HA group was 13.58%（P=0.005）higher than that in the LA group.（5）Effects on rumen microorganisms:comparing with CON,the relative abundance of rumen Prevotella was higher in LA sheep by 65.83%（P=0.001）and the relative abundance of rumen Christensenellaceae＿R-7＿group was higher（P=0.001）in MA sheep than in LA and HA by 61.80%and 36.10%respectively.The addition of C.chinense increased rumen fungal diversity in sheep,and the rumen microbial Observed-species index and Chao1 index of sheep in the LA group increased by 28.22%（P=0.046）and 33.01%（P=0.036）,respectively,compared to the CON.Addition of two functional native grasses modulated rumen fermentation parameters and relative abundance of microbial communities in sheep,increased serum antioxidant enzyme activity,improved digestive metabolism and promoted sheep growth.The addition of 1.67 g/kg BW of Capparis spinosa L.or 10%-15%DMI of Cynanchum chinense R.Br.to sown grassland grazing sheep in the Hexi oasis had a better effect on digestive metabolism.