PS5-10. Evaluation of Various Filter Bags for in vitro Digestion Method for Estimating the Ileal Digestibility of Crude Protein in Pigs

Abstract The objectives of the present study were to evaluate various filter bags used in a multi-sample 2-step in vitro procedure for swine feed ingredients and to develop prediction equations for estimating the standardized ileal digestibility (SID) of crude protein (CP) using in vitro ileal disappearance (IVID) of CP determined from both the conventional procedures using flasks (IVIDflask) and multi-sample procedures employing a DaisyII incubator with newly developed filter bags. Thirteen test ingredients used were corn, wheat, white rice, copra meal, palm kernel expellers, soybean meal, rice bran, soybean hulls, wheat bran, pea protein concentrate, skim milk powder, soy protein concentrate, and soy protein isolate. The filter bags used in the present study were F58, R55, polytwill, and polyester bags. In the conventional in vitro procedure, 10 mg of pepsin in step 1 and 50 mg of pancreatin in step 2 were used for each flask containing 1 g of feed sample. In the multi-sample simultaneous in vitro procedure, 12 to 24 samples, each enclosed in a filter bag, were digested in a jar of DaisyII incubator using 24 times the amount of buffer solution and enzymes of the conventional in vitro procedure. To select the appropriate filter bag, the concordance correlation coefficient (CCC) was calculated based on the IVIDflask of dry matter. The prediction equations for the SID of CP were developed using the IVIDflask of CP and the IVID determined from the multi-sample simultaneous in vitro procedure with the polytwill bag (IVIDpolytwill) of CP. The IVIDflask of DM was most highly correlated with IVIDpolytwill of dry matter among the filter bags (0.982 vs. 0.942 to 0.977). The IVIDflask of CP did not differ from IVIDpolytwill of CP in corn, white rice, wheat bran, soybean hulls, and soy protein concentrate. In wheat, soybean meal, palm kernel expeller, pea protein concentrate, and soy protein isolate, the IVIDpolytwill of CP was greater than IVIDflask of CP (P 0.05). On the other hand, in copra meal and rice bran, IVIDflask of CP was greater than IVIDpolytwill of CP (P 0.05). The prediction equations for SID of CP were developed: SID of CP, % = 0.956 × IVIDflask of CP, % – 2.243 (r2 = 0.737; P 0.001); SID of CP, % = 1.078 × IVIDpolytwill of CP, % – 6.308 (r2 = 0.841; P 0.001). In conclusion, the multi-sample simultaneous in vitro procedure using the polytwill bag can replace the conventional in vitro method for estimating SID of CP in swine feed ingredients.