| The objective of this experiment was to screen a preparation method for simulated intestinal fluid to determine the In vitro digestibility of amino acid of different kinds of protein feedstuffs in yellow-feathered broilers,according to the digestion level of protein in yellow-feathered broilers and the physicochemical properties of endogenous intestinal fluid,which will provide a basis for improving the accuracy of amino acid digestibility of feed estimated with the bionic digestion method for yellow-feathered broilers.Trial 1: Comparative study on hydrolysis characteristics of simulated broilers’ intestinal fluid prepared by different sources of digestive enzymesThe differences of enzyme composition,enzymatic properties and protein digestibility between simulated intestinal fluid and In vivo were investigated in trial 1.This trial was consisted of 3 parts.4 treatment levels were set for endogenous small intestinal fluid(ESIF),simulated small intestinal fluid 1(preparation of digestive enzyme purified powder from hollow intestinal fluid,SSIF1),simulated small intestinal fluid 2(preparation of pancreatic fluid,SSIF2)and simulated small intestinal fluid 3(preparation of digestive enzyme reagent,SSIF3).In the first part,the molecular weight distribution of proteins in four kinds of small intestinal fluids was investigated by gel electrophoresis.Each treatment had 5 replicates and each replicate had 1lane.In the second part,the hydrolytic properties of starch in wheat starch and corn starch and protein in casein and soybean protein concentrate were investigated with 3 replicates per treatment.The third part investigates the bionic degree of SSIF to ESIF.Single factor completely random design was adopted.The protein digestibility of 5 protein ingredients(soybean meal,cottonseed meal,rapeseed meal,casein and corn gluten meal)was measured in the bionic digestive system of monogastric animals.Each treatment had 5 replicates and each replicate had1 digestive tube.The results showed as follows:(1)The similarity of molecular weight distribution between SSIF1,SSIF2 and SSIF3 and ESIF was 88.2%、55.3 and 42.1%,respectively.(2)The hydrolysis rate of corn starch and casein in ESIF was close to that of SSIF1,the hydrolysis rate of soybean protein concentrate in ESIF was close to that of SSIF2,while the hydrolysis rate of wheat starch in ESIF was significantly different from that of the three kinds of small intestine fluids.(3)The digestibility of CP in the five diets of ESIF was less than 3.87% with SSIF1,2.88% with SSIF2,and 10.11%-64.57% with SSIF3.Trial 2: Comparative study on the digestibility of feed protein between small intestinal fluid and simulated intestinal fluid in broilersThe trial 2 was conducted to further investigate the differences between the simulated intestinal fluid,which was selected in the first experiment,and the In vivo intestinal fluid in molecular weight distribution of protein in the undigested residue of 5 feed ingredients after bionic digestion.The results showed that:(2)The similarity of ESIF and SSIF of the molecular weight distribution of soybean meal,cottonseed meal,rapeseed meal,corn gluten meal and casein residue was 69.9%,34.1%,90.1%,77.7% and 74.2%,respectively.The distribution of low molecular weight protein in ESIF digestible residue was significantly higher than that in SSIF group(P<0.05),and the distribution of high molecular weight protein in 103～132k Da was significantly lower than that in SSIF group(P<0.05),and this difference was more obvious in cottonseed meal.Trial 3:Comparative study on the digestibility of feed protein in broilers and bionic digestion of stomach-small intestineThis experiment was a validation experiment with the aim to investigate the difference and correlation between bionic digestion and In vivo digestion(animal metabolism test)on the amino acid digestibility of the diet(based on 5 protein feed raw materials)and the difference in molecular weight distribution between the undigested residue and fecal protein.Thirty21-week-old adult yellow-feathered broilers with cecum removed were randomly divided into 3groups with 5 replicates per group and 2 broilers per replicate according to body weight.The metabolic tests were carried out in 2 stages.In the first phase,the molecular weight distribution and amino acid digestibility of excreta of soybean meal,cottonseed meal and rapeseed meal diets were determined.The molecular weight distribution and amino acid digestibility of the excreta of corn gluten meal and casein were determined in the second phase,and the endogenous amino acid excreta was determined by the nitrogen-free diet.The results showed as follows:(1)The correlation between the digestibility of soybean meal,cottonseed meal,rapeseed meal,casein and corn gluten meal(excluding glycine)by biological method and bionic method was r=0.91,r=0.77,r=0.82,r=0.93 and r=0.87,respectively.(2)The similarity of molecular weight distribution of the digestible residues of soybean meal,cottonseed meal,rapeseed meal,corn gluten meal and casein by biological method and bionic digestion method were 93.3%,41.4%,74.5%,86.2% and 76.9% respectively;The protein distribution of biodigested feces in 40-95 k Da range was significantly higher than that in bionic digested feces group(P<0.05),and the protein band dist-ribution in low molecular weight range was significantly higher than that in bionic diges-ted feces group(P<0.05).Conclusion:Simulated small intestine fluid(SSIF1)prepared by purified powder of digestive enzymes from chicken hollow fluid was very similar to ESIF in enzyme composition.Although SSIF1 and ESIF have a great difference in the molecular weight distribution of protein in the digestible residues,they are similar in the digestible capacity of protein feed materials.The statistical analysis P values of amino acid digestibility measured by bionic digestion and In vivo digestibility were significantly different with different diets,but the correlation was good.In conclusion,this study provides a practical basis for the preparation of simulated small intestinal fluid. |
