| China's dairy industry has developed rapidly,the low contents of milk protein and milk fat which determined milk quality are the key factors to the development of the dairy industry.Currently,the main factors affecting the milk quality of dairy cows are dairy breeds,dietary types and environment.Among them,the dietary types have a significant effect on milk quality.Increasing milk quality has become the focus of dairy research by changing dietary patterns.In this study,based on the status of feed resources of dairy cows in China,the effect of different roughage diets on the metabonome and milk quality in dairy cows were studied.In this study,ten healthy lactating Chinese Holstein cows were randomly assigned to two groups(n=5)and fed with different diets respectively,corn straw(CS)or mixed forage(MF)diet.The experiment was divided into three stages,each stage was 30 days.We applied liquid chromatography-mass spectrometry(LC-MS)to analyze the metabolites in the breast(milk,mammary gland,breast arterial and venous blood),rumen fluid,liver and jugular vein of CS group and MF group cows,the purpose was to find the difference in the metabolites between CS group and MF group cows.The effect of two different roughage diets on milk quality in dairy cows was studied by measuring the difference of metabolites between CS group and MF group cows.The results showed that:(1)The contents of milk protein rate,milk fat rate,milk yield,milk protein yield,milk fat yield,total solids,dry matter intake of CS group were significantly lower than those in MF group cows(P<0.05),the contents of Lyso PC(16:0),hippuric acid,TG(30:0,36:0,37:0,38:0,40:0,42:0,46:0,50:4)in milk of CS group were significantly lower than those in MF group cows(P<0.05),the contents of acetylcarnitine,sn-glycero-3-phosphocholine,propionyl-L-carnitine,PC,carnitine were significantly higher than those in MF group cows(P<0.05).(2)The contents of L-leucine,L-arginine,palmitic amide,oleamide in mammary gland of CS group were significantly lower than those in MF group cows(P<0.05),the contents of hypoxanthine,xanthine,proline betaine ect.12 kinds of metabolites were significantly higher than those in MF group cows(P<0.05).(3)The contents of proline betaine,trimethylamine N-oxide,L-tryptophan,TG(55:1,62:0),PC(36:0,36:5,38:2),plasmenyl-PE(36:3)in breast arterial blood of CS group were significantly lower than those in MF group cows(P<0.05),the contents of propionyl-L-carnitine,hippuric acid,SM(41:2,42:2)were significantly higher than those in MF group cows(P<0.05).(4)The contents of PC(34:4,38:2,38:3,38:4,40:4),taurine,Lyso PC(18:3,20:3),L-arginine in breast venous blood of CS group were significantly lower than those in MF group cows(P<0.05),the contents of SM(32:1,40:2,42:2),TG(58:0),hippuric acid were significantly higher than those in MF group cows(P<0.05).(5)The contents of alanine,cysteine,lysine,methionine,tryptophan,valine,2-phenylpropyl butyrate,2-phenylpropyl isobutyrate,?-methylphenethyl butyrate,1-methyl-1-phenylethyl isobutyrate,isobutyric acid,acetate,propionate,acetic acid in rumen fluid of CS group were significantly lower than those in MF group cows(P<0.05),the contents of acetylcholine,trimethylamine,methylamine were significantly higher than those in MF group cows(P<0.05).(6)The contents of PC(30:0,34:3,38:1,38:4),histidine,hypoxanthine,uridine in liver of CS group were significantly lower than those in MF group cows(P<0.05),the contents of TG(51:3,52:2,52:3,52:4,53:2,53:3,54:0,54:2,54:3,54:4,54:5),plasmenyl-PC(42:0),plasmenyl-PE(36:2),PE(34:2,36:2,36:3),SM(42:2),acetylcarnitine,uric acid were significantly higher than those in MF group cows(P<0.05).(7)The contents of PC(36:0,36:2,38:1,38:2,38:3),TG(55:1,57:1,58:1,59:0,60:0,60:1),plasmenyl-PC(36:4,38:2),Lyso PE(20:1),citrulline,L-threonine in jugular vein of CS group were significantly lower than those in MF group cows(P<0.05),the content of SM(41:2)was significantly higher than that in MF group cows(P<0.05).(8)The expression of functional genes STAT5,AKT1,m TOR and CSN2 related to milk protein synthesis in mammary gland of CS group were significantly and extremely significantly lower than those in MF group(P<0.05,P<0.01),the expression of PTEN was significantly higher than that in MF group(P<0.05).The expression of functional genes ACC,FAS,SCD,SREBP1 c,FABP3 and PPAR? related to milk fat synthesis in mammary gland of CS group were significantly and extremely significantly lower than those in MF group(P<0.05,P<0.01).This study revealed that there was significant difference in breast(milk,mammary gland,breast arterial blood,breast venous blood),rumen fluid,liver and jugular vein nutritional metabonome,and in mammary gland functional genome related to lactation in mixed forage diets and corn straw diets.The results showed that mixed forage diet cows have significant advantages in the production and use of milk protein and milk fat synthesis precursors,and forward up-regulation of key functional genes related to milk protein and milk fat synthesis,which promote the synthesis of milk protein and milk fat.Mixed forage diet can increase milk protein yield and milk fat yield,milk protein rate and milk fat rate,and improve milk quality. |
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