Effects Of Different Concentrate To Forage Ratio On Nutrient Metabolism In Rumen And Liver Of Lactating Cows

Our objective of the current study was to assess the influence of different concentrate to forage ratio on splanchnic amino acid and fatty acid metabolism in dairy cows.Six multiparous mid-lactating Holstein cows were used in a randomized crossover trial with 2 dietary treatments:HC diet consisting of 40%forage and 60%concentrate or LC diet consisting of 60%forage and 40%concentrate diets.Treatment periods were 18 d,with 15 d for diet adaptation and 3 d for sample and data collection.Meanwhile,catheters were installed in the rumen,portal,hepatic vein,as well as one femoral artery of dairy cows,for measurimg the ruminal fermentation,amino acid(AA)and volatile fatty acid(VFA)metabolic change in the liver of dairy cows.The experiment included three parts:Experiment 1 The objective of this study was to discuss the effect of different concentrate to forage ratio on ruminal pH,VFA production in the rumen and metabolism in liver.The rumen fluid and blood samples were gained from the rumen,the portal,hepatic vein and as well as femoral arterial catheters,respectively,for 8 h from initial feeding.The results showed that:compared with LC diet,HC diet feeding remarkable decreased the rumen fluid average pH value(P<0.05).The pH decreased to minimum at 1 h and 2 h post-feeding,and the minimum pH values were 5.94 and 6.04 between HC diet and LC diet,respectively.The HC diet also could increase the concentrations of acetic,butyric acid,and Total VFA of rumen fluid,but there were no significantly effects by dietary treatment.However,the only VFA which markedly improved with feeding HC diet was propionate acid(P<0.05)and the feeding of LC diet tended to increased the ratio of acetate to propionate(P=0.06).In HC group,the concentration of acetate,propionate,butyrate and TVFA in the portal vein were markedly higher(P<0.05)than LC group.Moreover,HC diet remarkable improved the portal vein-arterial(P-A)concentration differences of acetate,propionate,butyrate and TVFA.However,the value of hepatic vein-portal vein(H-P)difference is negative,and the H-P concentration differences of propionate and butyrate were lower(P<0.05)in cows fed HC diets than LC diets.HC diet significantly increased the hepatic vein-arterial(H-A)concentration differences of acetate,propionate and TVFA(P<0.05).Experiment 2 The objective of this research was to consider the effect of different dietary concentrate to forage ratio on amino acids metabolic change in the liver of dairy cows.The results showed that:compared with LC group,the feeding of HC diet markedly improved the portal vein plasma concentration of essential amino acids(EAA)of Met,Lys,Ile,Thr,Val,His,and nonessential amino acids(NEAA)of Ser,Gly,Ala,Tyr,Asp,Arg,furthermore,dramtic increased the concentration of branched-chain amino acids(BCAA),Total EAA(TEAA),Total NEAA(TNEAA),Total AA(TAA)(P<0.05)in portal vein.Except Leu and Thr,The feeding of HC diet remarkable improved the concentration of EAA(P<0.05)in hepatic vein plasma.Compared with LC diet,HC diet significantly increased the hepatic vein concentration of Tyr and Asp,BCAA,TEAA and TAA(P<0.05).Moreover,the hepatic concentration of Thr,Arg tended to increased(P=0.08)in HC group than LC group.Compared to LC diet,HC diet significantly improved EAA concentration(P<0.05),except Leu,and the NEAA of Tyr,Asp,Arg also markedly increased(P<0,05)in femoral artery.HC diet increased significantly the concentration of BCAA,Total EAA and Total AA(P<0.05),while there were not markedly effects(P>0.05)on the concentration of TNEAA in femoral artery.Experiment 3 The aim of this research was to consider the effect of different dietary concentrate to forage ratio on the lactation performance and the change of glucose,urea,NEFA,?-hydroxybutyrate,GH,IGF-1 in splanchnic plasma.The results showed that:HC diet markedly improved(P<0.05)the portal,hepatic and arterial plasma concentration of glucose,nonesterified fatty acid and ?-Hydroxybutyrate.While,there were no significantly difference(P<0.05)on portal plasma concentration of insulin,glucagon and urea in two different concentrate to forage ratio of diets.Compared to LC group,HC diet markedly improved the hepatic vein plasma concentration of insulin and urea,but the hepatic concentration of GH and IGF-1 were not increased significantly(P>0.05).And in femoral artery,the feeding of HC diet significantly increased glucagon and urea concentration(P<0.05).Moreover,HC diet remarkable increased milk protein,TS and SNF concentration(P=0.05),and tended to promoted lactose concentration(0.05<P>0.10).