Determination of peptide nitrogen in ruminant digesta

In the present experiment, the cattle digesta from the rumen and abomasum were used to establish a moderate method for the determination of the peptide nitrogen content of the ruminant gastrointestinal digesta using the L₉ (3⁴) orthogonal design. The effects of the Tris-HCl buffer concentration (0.02, 0.04, or 0.06 mol·L^–1), Tris-HCl buffer pH (6.8, 7.4, or 8.0), ratio of dry digesta to Tris-HCl buffer (1∶15, 1∶20, or 1∶25), and extraction time (40, 60, or 80 min) on the determination of the peptide nitrogen content in the cattle gastric digesta were studied. The results show that the moderate separation conditions of nitrogen from cattle gastric digesta were 0.06 mol·L^–1, 6.8, 1∶25, and 60 min, respectively, and the maximum contents of peptide nitrogen were 14.97 mg·g^–1 and 19.28 mg·g^–1 in the rumen and abomasum digesta, respectively.