Study On Digestion And Metabolism Of Rumen And Limiting Amino Acid Of Lacting Cow Fed Hight Forage Diets

Thestudyincludestwoparts:The First part was conducted to study the rumen digestion and metabolism, the flow of the duodenaldigesta passage and amino acids with two marks in diets of high forage. Ration were composed of cornmeal, wheat middlings, soybean meal, and Chinese wildrye. Intake of CP was 13.25%.The result showedthe rumina fluid pH values was 6.0-6.8.The ammonia-N Concentration in rumina fluid was 4-13mg/100mL.Therumenfermentationwanacetatepropionic.Theduodenaldigestapassageflow16.25kg/d.The secondpartwasconducted to studyrationsofratio ofconcentrate to foragewas30:70, theeffectsof amino acid infusion on dairy cow's milk performance and limit amino acids. Four multiparous Holsteincows with rumen and duodenal cannulas were used with 4X4 Latin square at late stages of lactation.Treatment were duodenal infusions of 1) Lys, 2) Met, 3) Lys plus Met, and 4) ten essential amino acid;periods were 8 d . Milk production, content and yield milk protein, plasma concentrations of amino acid,plasma urea nitrogen and hormone were monitored. The result shown milk protein yield and fat yield withLys plus Met were greater Lys and Met infusion. Plasma urea nitrogen, glucose, growth hormone were notaffected by infusion. Plasma Lys and Met were significant increased with correspond to Lys and Metinfusion,butmammaryAVdifferenceofLysandMetwerenotaffectedbyinfusion. PlasmaconcentrationsofHiswithLMinfusionwassignificantlowercomparewithMetinfusion.ExtractionofplasmaaminoacidwithMinfusionandLMinfusionwerehigherthanLinfusion.Thestudyshowed LysandMetwerecolimitingaminoacidandHismaybethesecondlimitingaminoacidwhenrationsofratioofconcentratetoforagewas30:70.