Estimating Intestinal Digestibility of Feedstuffs for Ruminants Using Three-step in Situ-in Vitro and in Vitro Procedures
The overall objective of this thesis was to develop and establish a completely laboratory-based in vitro procedure for estimating (small) intestinal digestibility of ruminally undegraded feed protein. Intestinal protein digestibility (IPD) was estimated with a three-step in situ-in vitro procedure (ISIVP) and a mobile-bag technique (MBT). When using ISIVP, Feed samples were first incubated in the rumen of fistulated cattle for 16 h, then the residues were incubated in pepsin-HCl solution (pH 1.9) for 1 h and the residues of this step were incubated in pancreatin solution for 24 h. An enzymatic in vitro procedure (EIVP) was developed and established by replacing the 16 h rumen incubation step with 18 h protease (from Streptomyces griseus ) incubation. In conclusion, the EIVP could be applied to estimate the IPD of forages and concentrates covering a wide range of sources and CP concentrations, and thus, the completely laboratory-based, standardized EIVP can replace the more invasive ISIVP for estimating IPD of a wide range of feedstuffs for ruminants.