Study On The Method For Assessment Of Endogenous Metabolic Glucose In Pig Diet

This paper studied the evaluation method of endogenous metabolic glucose in pig diet.First,the“stable isotope tracer method”was used to infuse ¹³C-VFA（acetic acid,propionic acid and butyric acid isotope）into the end of the pig ileum to trace the traces of volatile fatty acids produced by the pig’s large intestine,and to obtain blood and intestinal wall tissue.Large intestine contents sample.A method for determining the acetic acid,propionic acid and butyric acid and the respective isotopic contents of pig blood,large intestine tissue and large intestine contents by GC-MS（gas phase mass spectrometry）was established.The animal feeding experiment was carried out again,and the absorption of the propionate and the net absorption of the portal vein were calculated by using the“ileum end perfusion method”and the“dynamic-vein concentration difference method”combined with the isotope tracer.According to the calculation formula of endogenous metabolic glucose in pig diet,the endogenous metabolic glucose content of pig diets with three different metabolic glucose levels was obtained.Finally,the above three diets were digested by in vitro simulated“stomach-small intestine”,and the in vitro simulated large intestine microbial fermentation was carried out to determine the production of propionic acid and lactic acid.The production of propionic acid and lactic acid in vitro was analyzed by regression analysis with the amount of propionate absorption in the body and the net absorption of portal lactic acid.Through the regression equation between them,a method for estimating the endogenous metabolic glucose of the diet was established,and the endogenous metabolic glucose values of the four raw materials of corn,soybean meal,soybean hull and wheat bran were estimated by this method.The paper is divided into three parts:Part 1:Study on the determination of ¹³C labeled volatile fatty acids by GC-MSA healthy growing pig weighing about 30 kg was selected and fed a diet based on corn and soybean meal.Three days after the pre-feeding,the test pigs were fitted with a“T”type fistula at the end of the ileum,a femoral artery,and a portal vein vascular fistula.After the operation was resumed,the isotope ¹³C-labeled acetic acid,propionic acid,and butyric acid were infused from the ileal“T”type fistula.At the end of the perfusion,blood was collected,and the pigs were slaughtered,and the entire intestine of the cecum,colon,and rectum was collected and weighed,and the contents of the three segments of the intestine were collected.A method for determining the levels of¹³C-labeled and unlabeled acetic acid,propionic acid,butyric acid in blood,intestinal tissue,and intestinal contents by gas phase mass spectrometry was established by setting and adjusting the GC-MS conditions.The results show that the six VFAs have a good linear relationship within the corresponding concentration range.In-batch precision and inter-assay precision and accuracy are good.This study can be used as a simple,rapid and accurate method for the analysis of ¹³C stable isotope-labeled volatile fatty acid content in pig blood,large intestine tissue and large intestine contents.Part 2:In vivo method to assess endogenous metabolic glucose levels in three diets of growing pigs15 healthy growing pigs with an average body weight of 30 kg were randomly divided into 3 treatment groups,5 replicates in each treatment group,and 3 days with different nitrogen and metabolic glucose levels based on corn and soybean meal.grain.Three days after the pre-feeding,the test pigs were fitted with a“T”type fistula at the end of the ileum,a femoral artery,a portal vein,and a mesenteric vasculature.After the operation and the feed intake returned to normal,the aminopurine acid was perfused from the distal end of the mesenteric vasospasm,and the isotope ¹³C-labeled propionic acid was perfused from the ileal“T”type fistula.Blood samples from the portal vein and femoral artery were collected.After the end of the infusion,the pigs were slaughtered and the entire intestine of the cecum,colon and rectum was collected and weighed.The content of propionic acid and propionic acid isotopes in the blood and intestinal wall was determined by the method in Part 1.The lactic acid content in the blood was measured using a kit.The net absorption of propionic acid and lactic acid in the portal vein was calculated using the“dynamic-vessel concentration difference method”.According to the net absorption of lactate portal vein and the absorption of propionic acid in the large intestine,the endogenous metabolic glucose level of the diet was calculated.The results showed that the net absorption of propionic acid portal vein was the lowest in diet group I and the highest in diet group II,and the difference between the three groups was not significant（P>0.05）.The concentration of propionic acid in the large intestine was the highest in the diet group I,and the lowest in the diet group III and significantly lower than the diet group I（P<0.05）.The absorption of propionic acid in the large intestine was the lowest in the group III,and the highest in the diet group I was significantly higher than that in the diet group III（P<0.05）.The net absorption of lactate portal vein was the highest in group III,and the lowest in group II and significantly lower than group III（P<0.05）.The endogenous metabolic glucose content of the three diets in the growing pigs was the lowest in the diet group II,and the highest in group I and significantly higher than that in group II（P<0.05）.The endogenous metabolic glucose content of the three diets in the growing pigs was the highest in the diet group I,and the lowest in the second group and significantly lower than the I group（P<0.05）.Under the conditions of this experiment,the absorption of propionic acid in the three diets was15.21,13.33 and 8.13 g/d,respectively,and the net absorption of lactate portal vein was 7.57,3.17 and 12.04 g/d,respectively,and the endogenous metabolic glucose level was 61.07,respectively.44.22 and 55.10 g/kg.By combining ¹³C propionic acid tracer,the absorption of propionic acid in the large intestine was studied,and the accuracy of the method for measuring endogenous metabolic glucose in the diet was improved.Part 3:In vitro evaluation of endogenous metabolic glucose levels in three diets of growing pigsThe diet in Part 2 was sifted and sieved as a substrate,and after“stomach-small intestine digestion”was simulated in vitro,the residue was collected and dried and pulverized.The in vitro fermentation gas production method was further studied to determine the content of propionic acid and lactic acid produced by fermentation.The production of propionic acid and lactic acid in vitro was analyzed by regression analysis with the amount of propionate absorption in the body and the net absorption of portal lactic acid.Through the regression equation between them,the method of estimating endogenous metabolic glucose in diet was established,and the content of endogenous glucose in the four feed ingredients of corn,soybean meal,soybean hull and wheat bran was determined.The results showed that there was a good linear relationship between the absorption of propionic acid in the intestine and the amount of propionic acid produced in vitro,the net absorption of lactate portal vein and the amount of lactate produced in vitro at 48 h.Under the conditions of this experiment,the relationship between the absorption of propionic acid in the three diets and the amount of propionic acid produced in vitro in the three diets was Y=3.8268X-6.8329,R²=0.9683;the net absorption of lactate portal vein in vivo the relationship between the amount of lactic acid produced in vitro and fermented was Y=0.5900X+3.1967,and R²=0.9666.Based on these two expressions,an in vitro estimation method for determining the endogenous metabolic glucose level of the diet was established.Through this method,the endogenous metabolic glucose contents of the four commonly used feed ingredients corn,soybean meal,soybean hull and wheat bran were estimated to be 177.55,32.83,58.02 and 14.83mg/g,respectively.