The Effects Of Different Of Concentrate To Forage Ratio On The Fatty Acid Metabolism,Glycometabolism And Expression Of Related Metabolic Genes In Mid-lactating Dairy Cows

The objective of the current study were to assess the mechanism of different concentrate to forage ratio on the fatty acid metabolism,glycometabolism and expression of related metabolic genes of liver in mid-lactating dairy cows.Eight cows established rumunal cannulation and chronic vascular catheter in mid-lactating period were chosen to evaluate the metabolism of fatty acid in rumen,fatty acids,amino acid,metabolism and expression of related metabolic genes in liver.The experiment included three parts.Exp.1 This study was to discuss the effect of the different concentrate to forage ratio on VFA and LCFA in the rumen liquid and hepatic vein plasma.Eight multiparous Chinese Holstein lactating dairy cows(BW,512±36 kg)were randomly assigned to two groups.One group was fed a total mixed ration(TMR)diet contained HC diet(60%concentrate +40%forage)and the other group was offered a TMR diet contained HF diet(60%forage +40%concentrate).The results showed that:compared with HF diet,HC diet remarkable increased propionate concentrations,and decreased acetate to propionate ratio in the rumen liquid(P<0.05).The HC diet also could decrease the concentrations of palmitic(C16:0),palmitoleic(C16:1 cis-9),linoleic(C18:2 cis-9,12),tricosanoate(C23:0),tetracosenoic(C24:1)(P<0.05),but the feeding of HC diet tended to decrease the concentration of octanoic(C8:0)(P=0.06),polyunsaturated fatty acid(PUFA)(P=0.07).However,HC diet remarkable increased unsaturation index C18:0/C18:2 cis-9,11 and C18:2 trans-9,11(P<0.05).In HC diet group,the concentration of propionate in the hepatic vein plasma were markedly higher(P<0.05)than HF diet group and the feeding of HC diet tended to increased concentration of butyric(P=0.06).Moreover,the HC diet can significantly decrease the concentrations of hendecanoic(C11:0),palmitoleic(C16:1 cis-9),heptadecenoic(C17:1 cis-10),linoleicacid(C18:2 cis-9,12),eicosadienoic(C20:2),teracosanoic(C24:0),timnodonic(C20:5 n3),tetracosenoic(C24:1),docosahexaenoic(C22:6),monounsaturated fatty acid(MUFA)and PUFA(P<0.05),but significantly increased the concentrations of epoxyeicosatrienoic(C22:1 n9)and the value of C18:0/C18:2 cis-9,11 and C18:2 trans-9,11(P<0.05).Expt.2 The objective of this research were to evaluate the effect of different dietary concentrate to forage ratio on composition of milk and biochemical parameter,hormone and AA in plasma of dairy cows.The results showed that:compared with HF group,the milk yield,percentage of milk protein,percentage of lactose and lactose yield were higher(P<0.05)in the HC diet,however,the milk fat yield and percentage were remarkable lower(P<0.05)in the HC diet.The plasma non-esterified fatty acid(NEFA),low-density lipoprotein cholesterol(LDL-C),p-hydroxybutyric(BHBA)and triglyceride(TG)concentrations were significantly(P<0.05)increased when the cows were fed with HF diet compared with HC diet.The plasma glucagon(GC)and ammonia concentrations were significantly elevated(P<0.05)in HC diet.The HC diet also could decrease the concentrations of lysine(Met),asparaginate(ASP),alanine(Ala)and glutamic(Glu)compared with the HC diet.Expt.3 This experiment was to study the effect of different dietary concentrate to forage ratio on the glycometabolism,fatty acid metabolism and expression of related metabolic genes of liver in mid-lactating dairy cows.Acetyl-CoA carboxylase(ACC),diacylglycerol O-acyltransferase 1(DGAT1),Acyl-CoA synthetase long-chain(ACSL)and microsomal triglyceride transfer protein(MTTP)were down-regulated markedly(P<0.01)in the HC diet.The Sterol regulatory element-binding protein 1(SREBF1)mRNA abundance was significantly decreased(P<0.01)in the HC diet.The mRNA expressions of acyl-Coenzyme A dehydrogenase(ACADL)(P<0.05)and carnitine palmitoyltransferase 1A(CPT1A)(P<0.01)were markedly up-regulated in the HF diet.mRNA expression of PC was increased(P<0.05)in the HC diet.The mRNA expression of 3-hydroxy-3-methylglutaryl-CoA synthase 2(HMGCS 2)was significantly up-regulated(P<0.01)in the HF diet.Western blotting analysis showed that the protein levels of CPT1A,G6PC and SREBF1 were significantly increased(P<0.05)in the HC diet compared with the HF diet.As above-mentioned,compared with HF diets,the concentrition of propoinate in rumem fluid and heptaic vein were increased significantly and decresed LCFA concentration in cows fed HC diets.The percentage of milk lactose and protein were markedly higher and the percentage of milk fat was markedly lower in cows fed HC diets.HC diets increased contents of glucose,ammonia-N and glucagon.The PC mRNA abundance was significantly decreased,the SREBF1,ACSL,ACADL,CPT1A,G6PC and HMGCS2 mRNA abundance were significantly increased and the SREBF1,CPT1A and G6PC protein expression markedly up-regulated in the HC diet.