Abstract

Endogenous protein loss at the end of the small intestine was determined in two experiments using 10 pigs surgically prepared with end-to-end ileo-rectal anastomosis to allow total collection of ileal digesta. In the first experiment pigs were fed graded protein levels of 0 (protein-free), 55, 110 or 165 g/kg diet. Optimal durations for the adaptation and collection periods were found to be 4 and 3 d, respectively (combination 4:3), as shown by the higher correlation coefficient (r2 = 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 endogenous N and amino acids were less accurate and tended to be smaller (P < 0.20) when obtained by extrapolation to zero nitrogen intake than when measured in pigs fed the protein-free diet. The endogenous protein was rich in proline, glutamic acid, glycine, aspartic acid, serine and threonine. In comparison to other amino acid patterns, this composition 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 endogenous losses of nitrogen and amino acids per kilogram of dry matter intake (P < 0.05), but the excretion reached a plateau at higher dietary fiber concentration (102 g/kg). In contrast, glucosamine and galactosamine 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.

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