Study On Predicting Model Of The Absorbed Amino Acids Fluxes In The Small Intestine Of Ruminants

The objective of this study was to establish a predicting model of the absorbed amino acids flow in the small intestine of ruminants.The carbohydrat and protein fractions of 18 kinds of feedstuffs were analyzed based on the motheds in Cornell Net Carbohydrate and Protein system (CNCPS) of recommended,and then rumen degradation rate and small intestinal digestion rate of protein were determined by nylon bags technique and a three-step in vitro procedure.Using the least-squares fitting parameters the rate parameters of rumen degradation and small intestine digestion were determined to establish a predicting model of the absorbed animo acids flow in the small intestine of ruminants,the establishment of the ruminant small intestine to absorb amino acids flow predicting model.Animal experiments was conducted in sheep to verify the model and get more appropriate corrections.Part 1:Establishment of a predicting model of the absorbed animo acids fluxes in the small intestine of ruminantsFour multiparous,ruminally cannulated Holstein-Friesian milking cows (BW=507±87kg),with the similar milk production performance,were used to evaluate 18 kinds of feedstuffs nutrition value by the rumen nylon bag method.At the same time,the ration of five protein fractions and ruminal degradation rate of protein fractions of B1,B2 and B3 of 18 general feedstuffs were determined,and the parameters of rumen degradation rate can be obtained after Data Processing with the least-squares method,not considering the differences in amino acid profile of protein fractions B1,B2 and B3.Therefore,this study chose the alfalfa,DDGS,corn and the degradation times of residues to analyze their amino acid profiles after residues pretreated with the protein used for the CNCPS.The profile of protein was determined by the methods in recommended CNCPS,to establish a more accurate prediction model.The method of small intestinal digestion rate parameters was established by the improvement of the three-step in vitro procedure(Calsamiglia and Stern,1995 ).Under the acidic conditions,abomasum was replaced with the activated pepsin,and then pancreatin was used to digest the degradation residues under the weak alkaline conditions(PH = 7.6).CP content was determined by Kjeldahl method.Fitting the data to obtain the B1,B2,B3 intestinal digestion rate constant.The results showed that there is significant difference between the rate parameters of rumen degradation and the predicted value by CNCPS,which is also similar of the rate parameters of small intestine digestion.The results showed that the degree of protein fraction C digestive absorpation varied in 10 raw materials.Part 2:Model verificationThe study was conducted with three similar body weight(BW = 60±3kg),1.5-year-old female sheeps,with rumen cannulas,duodenal cannulas and ileal cannulas.Two experiments were involved.Cottonseed meal was the major source of protein in the experiment 1,while soybean meal in the experiment 2.Three dietary concentration gradients were set to meet the demand of 70%,100%,130%of maintain ability,respectively.At the fifth day of trial,tag feed fed chromium was used to determine its rate of rumen outflow; 14 days after feeding,chyme was collected totally for three days through duodenal cannulas and ileal cannulas.AA composition was determined after being dried,to verify the established model.The results show that the CNCPS estimated value is higher than the value of'sheep measured with the absorbed amino acids fluxes in the small intestine.Beacause of MCP flow may be overestimated by CNCPS.