| This experiment focused on the digesta transit time and particle size in the intestinal tract of growing pigs and established an in vitro digestion method for predicting the digestible and metabolizable energy of cereal grains for growing pigs based on the third-generation simulated digestion system(SDS-3).The experiment 1 was to investigate the effects of dietary fiber levels and feeding time on the passage rate of digesta in the intestinal tract of growing pigs.The dietary crude fiber level at 3.39 or 5.56%and feeding time of 8:00 or 16:00 were used in a 2?2 factorial completely randomized arrangement.Twenty-four growing pigs(Duroc?Large,21.9±1.62 kg initial BW)were surgically fitted with simple T-cannulas at the anterior duodenum or distal ileum(average initial BW of the experiment was 49.5±3.26 kg).The time of appearance and disappearance of ferric oxide were observed on the anterior duodenum,terminal ileum and the total digestive tract.The results showed that:1)The dietary fiber levels and feeding time had significant effects on the passage rate of digesta in the anterior duodenum,the terminal ileum and the total digestive tract(P<0.01).The higher dietary fiber level increased the passage rate of digesta.The passage rate of digesta in pigs fed at 8:00 significantly faster than that in pigs fed at 16:00.2)The average transit time of diet were 3.54 h at the anterior duodenum,9.07 h at the terminal ileum,and 40.24 h across the total digestive tract,respectively.The experiment 2 was to investigate the effects of water volume,sample weight and sieving time on the mean particle size of pelleted diet,digesta and feces using wet-sieving.The water volume of 1,1.25or 1.5 L,sample weight of 7.5 or 10 g for pellets,15 or 30 g for ileal digesta,10 or 20 g for feces and sieving time of 4 or 5 min were used in a 3?2?2 factorial completely randomized arrangement.The mean particle size of diets,digesta and feces were measured for different wet-sieving conditions.The results showed that:Water volume and sample weight significantly affected the determination of mean particle size for pelleted diet,ileal digesta and feces(P<0.01),but significant effect of the sieving time was only observed on the determination of ileal digesta(P<0.05).The determined values of particle size were significantly higher in 1 L than 1.25 L or 1.5 L of water(P<0.05).Moreover,particle size was significantly different between 1.25 L and 1.5 L of water for determining of feces(P<0.05),but there was not significant difference between 1.25 L and 1.5 L of water for the particle size determination of pelleted diet and ileal digesta,and the absolute bias was no more than 6μm.The sample weight ranged from 7.5 to 10 g for pelleted diet,15 to 30 g for ileal digesta,and 10 to 20 g for feces led to the difference of less than 12μm in determined particle size.The experiment 3 was to investigate the effect of dietary particle size on the profile of intestinal digesta and fecal particle size,digestive enzyme activity and apparent total tract digestibility of nutrient in growing pigs.A two-sample completely random design was adopted in this study.Diets 1 or 2(average particle size were 390μm and 511μm,respectively)were randomly provided for each of 2 groups of duodenal cannulated pigs(6 pigs per group)and each of 2 groups of ileal cannulated pigs(6 pigs per group)[average initial BW of experiment was 29.1±1.58 kg].The particle size of diets,duodenal digesta,ileal digesta and feces,digestive enzyme activities of duodenal fluid and nutrients digestibility were measured for diets 1 and 2.The results showed that:1)Compared diet 1 with diet 2 fed to pigs,the average size were 180 vs.287μm for duodenal digesta(P<0.01),247μm vs.333μm for ileal digesta(P<0.01),and 191μm vs.289μm for feces(P<0.01),respectively.2)No significant differences were observed in the activities of amylase,trypsin and chymotrypsin in the duodenal fluid and the total tract digestibility of nutrients for the growing pigs fed with diets 1 and 2.The experiment 4 was to design the simulated the total tract digestion procedure using simulated digestion system(Model SDS-3)to predict the concentration of DE or ME in cereal grains based on the parameters of the passage rate and particle size of digesta in intestine of growing pigs determined in experiment 1,2 and 3.A single-factor completely random design was used to determine the enzymatic hydrolysate gross energy(EHGE)of 14 cereal grains using SDS-3.In bioassay,15 borrows(30.2±2.4 kg of initial BW)were randomly allotted to a 15?6 incomplete Latin square design with 15 diets and six periods to determined DE and ME content in 15 diets(14 cereal grains diets and 1 basal diet).The results showed that:Ratio of EHGE to DE or ME in 14 cereal grains was ranged from 0.90 to 1.07 for EHGE/DE,or 0.93 to 1.10 for EHGE/ME,respectively.The regression of DE or ME on EHGE in 14 cereal grains was DE=0.9198×EHGE+351(R~2=0.81;RSD=128 kcal/kg;P<0.01),or ME=0.9087×EHGE+301(R~2=0.84;RSD=113 kcal/kg;P<0.01). |
