An in vitro ileal disappearance procedure for estimating ileal digestibility of protein in weanling pigs

Objective: The present experiment aimed to develop an in vitro procedure for estimating standardized ileal digestibility (SID) of crude protein (CP) in feed ingredients for weanling pigs by modifying the conventional procedure for growing pigs.Methods: In the conventional in vitro ileal disappearance (IVID) procedure, sample solutions added with 1 mL of pepsin (10.0 g/L) are incubated for 6.0 h in step 1 to simulate digestion in the stomach followed by adding 1 mL of pancreatin (50.0 g/L) and incubating for 18.0 h in step 2 to simulate digestion in the small intestine.To develop an IVID procedure for weanling pigs, 3 incubation periods (6.0, 4.5, and 3.0 h in step 1 and 18.0, 13.5, and 9.0 h in step 2) and 3 enzyme concentrations (pepsin 10.0, 7.5, and 5.0 g/L in step 1 and pancreatin 50.0, 37.5, and 25.0 g/L in step 2) were tested in a 3×3 factorial arrangement.Test ingredients were rice, corn, wheat, rapeseed meal, soybean meal, fermented soybean meal, and soy protein concentrate.Results: The IVID of CP measured using the conventional procedure deviated from the weanling pig's in vivo SID of CP by 5.0% on average.Based on the quadratic response surface analysis, the use of 1 mL of pepsin at 7.6 g/L with the incubation period of 4.4 h in step 1 followed by adding 1 mL of pancreatin at 38.1 g/L with the incubation period of 13.3 h in step 2 minimized the absolute difference between IVID of CP and in vivo SID of CP to 3.6% on average for weanling pigs. Conclusion:The in vitro procedure for weanling pigs was developed by lowering the incubation periods and enzyme concentrations for estimating ileal digestibility of protein in feed ingredients with greater accuracy compared with the conventional in vitro procedure.