Study On The In Vitro Method To Predict The Digestibility Of Energy And Crude Protein Of Feeds In Pigs Using The Simulative Digestion System

The effect of dietary fiber level on the nutrient digestibility and digestible energy ofgrowing-fattening pigs was determined in the present study. The effects of factors on the in vitronutrient digestibility of feeds were also analyzed using simulative digestion system (SDS-ΙΙ). Thefeasibility of assaying the in vitro digestibility of energy and crude protein in diets and feed ingredientsusing the SDS-ΙΙ was evaluated by comparing the in vitro and in vivo nutrient digestibility. The in vitromethod for simulating nutrient digestion in swine hindgut was focused in the present study to improvean establishment of a quick and accurate system for feed evaluation, which based on the in vitro methodto simulate digestion in the stomach and small intestine.The objective of Exp.1was to determine the effects of fiber level from alfalfa meal andexperimental period on the intestinal nutrient flow and hindgut fermentation of growing pigs, in order toprovide data for an establishment of a feed evaluation system using the SDS-ΙΙ. Twenty-four pigs wereprepared by T-cannula insertion into the distal ileum and allotted to4treatments. The pigs wereprovided a control diet or a diet in which corn and soybean meal partly were replaced by5,10and20%,respectively, of alfalfa meal to give the graded levels of dietary fiber during two10-d experimentalperiods (12.3,14.6,16.9and21.4%dietary fiber). The apparent ileal digestibility (AID), apparent totaltract digestibility (ATTD), and hindgut fermentation of dry matter (DM), carbohydrates (CHO), andgross energy (GE) decreased (linear, P <0.05) as the dietary fiber level increased. The intestinal flow ofDM, CHO, and GE increased (linear, P <0.05) with raising the level of dietary fiber. The pH in the ilealdigesta and the concentration of acetate, propionate, and total VFA in the feces increased (linear, P <0.01) as the fiber level increased. From experiment period1to period2, the ATTD and hindgutfermentation of CHO reduced (P <0.01), whereas the concentrations of propionate, valerate, and totalVFA in ileal samples increased (P <0.05). A multiple linear regression analysis taking into accountboth the soluble and insoluble fiber intake explained the main variation (P <0.05) in the total tractdigestibility and flow of nutrients.The objective of Exp.2was to determine the effects of the factors on the in vitro nutrientdigestibility of feeds to provide a method for meaning the in vitro nutrient digestibility of feeds usingthe SDS-ΙΙ. After preliminary consecutive incubations to simulate digestion in stomach and smallintestine, the in vitro generation rate of reducing sugar (RGG) in all feeds reached maximal value as invitro hindgut digestion for6h, the RGG was greater in wheat bran than in corn and soybean meal (P <0.05). The cellulase concentration did not affect the RGG and in vitro energy digestibility (ED)(P>0.05). The ED of wheat bran during wash times of undigested residues for6times was significantlygreater than for3times (P <0.05). No significant differences were revealed on the in vitro dry matterdigestibility (DMD) of feeds using two preliminary methods of dialysis tube (P>0.05). Removing theoil and fat from undigested residues, the DMD of corn, soybean meal and wheat bran were increased by3%, and the in vitro ether extract digestibility of feeds was more than90%(P <0.05), but the in vitro digestibility of other nutrients was not affected by this method (P>0.05). The DMD of feeds wasdifferent in the pushing and pulling method of running direction of peristaltic pump (P<0.05). Althoughthe DMD of feeds was less in the pushing method than in pulling, the results with well accuracy andprecision were obtained in pushing method.The objective of Exp.3was determined the in vitro nutrient digestibility of feeds compared withthe in vivo value, so as to evaluating the feasibility of assaying the digestibility of nutrients and energyby the bionic method. The in vitro nutrient digestibility varies in different feed and in different segmentsof simulated digestion. The correlation of digestibility of dry matter (R2=0.99), organic matter (R2=0.97) and energy (R2=0.97) of fiber diets using the in vitro and in vivo method was very high (P <0.01). The in vitro nutrient digestibility was negatively correlated with the content of dietary fiber (P <0.05). The absolute differences between the in vitro and in vivo digestible energy was0.50±0.24MJ/kg(P <0.05). The correlation of the digestibility of dry matter (R2=0.97, P <0.01), organic matter (R2=0.98, P <0.001), crude protein (R2=0.82, P <0.05), energy (R2=0.93, P <0.01) and the digestibleenergy (R2=0.93, P <0.01) of feed ingredients using the in vitro and in vivo method was also very high.The coefficient of variation (0.25~0.84%) of the in vitro energy and protein digestibility was less thanthe coefficient of variation (1.00~3.25%) of the in vivo energy and protein digestibility (P <0.05),which indicated that it can more accurately evaluate digestibility of energy and crude protein in swinefeeds using the in vitro method by the SDS than using the in vivo method.