Evaluation of two external markers for measurement of ileal and total tract digestibility of pigs fed human-type diets1

External markers for determination of nutrient digestibility have often been evaluated in conventional dry feeds but less often in conventional feeds such as human-type diets used in animal model studies. In the present study, 5 ileal-cannulated pigs were fed 5 types of soft bread-based diets supplemented with Cr(2)O(3) and AIA as digestibility markers for 1 wk in a Latin square design. Ileal contents were collected twice for 5 h and a fecal grab sample was obtained once per week. Ileal and total tract digestibility of OM and nonstarch polysaccharides (NSP) based on the 2 markers were compared by linear regression. Across dietary treatments and site of collection, high correlation existed between digestibility values obtained with Cr(2)O(3) and AIA, resulting in a R(2) > 0.77 (P < 0.001) and a linear relation close to unity. For ileal samples, the correlation was poor, particularly for NSP, which had R(2) = 0.09 (P = 0.14) whereas OM had an R(2) = 0.52 (P <0.001). On the other hand, fecal grab samples led to R(2) > 0.92 (P < 0.001) for both OM and NSP. However, AIA gave higher values than Cr(2)O(3), particularly in samples with lower digestibility. The discrepancy is presumably caused by analytical difficulties due to a high fecal ash contents or interference with other components in the human-type diets.