ENDOGENOUS AMINO NITROGEN COLLECTED FROM PIGS WITH END-TO-END ILEORECTAL ANASTOMOSIS IS AFFECTED BY THE METHOD OF ESTIMATION AND ALTERED BYDIETARY FIBER

Endogenous protein loss at the end of the small intestine was determin ed in two experiments using 10 pigs surgically prepared with end-to-en d ileo-rectal anastomosis to allow total collection of ileal digesta. In the first experiment pigs were fed graded protein levels of 0 (prot ein-free), 55, 110 or 165 g/kg diet. Optimal durations for the adaptat ion and collection periods were found to be 4 and 3 d, respectively (c ombination 4:3), as shown by the higher correlation coefficient (r(2) = 0.95) between excreted and ingested nitrogen compared with the other combinations tested (5:2, 5:3, 9:3, 9:5). The estimated amounts of en dogenous N and amino acids were less accurate and tended to be smaller (P < 0.20) when obtained by extrapolation to zero nitrogen intake tha n when measured in pigs fed the protein-free diet. The endogenous prot ein was rich in proline, glutamic acid, glycine, aspartic acid, serine and threonine. In comparison to other amino acid patterns, this compo sition suggested a low bacterial contamination of the digesta. In the second experiment three levels of dietary fiber from wheat straw, corn cobs and wood cellulose were studied in pigs fed protein-free diets. Between 17 and 34 g crude fiber/kg diet, fiber increased the endogenou s losses of nitrogen and amino acids per kilogram of dry matter intake (P < 0.05), but the excretion reached a plateau at higher dietary fib er concentration (102 g/kg). In contrast, glucosamine and galactosamin e excretion increased continuously and linearly (P < 0.05) with fiber intake. We conclude that endogenous amino acid loss may be considered constant at usual and high levels of the fibrous mixture under study.