Effect of increasing dietary fermentable fiber on diet nutrient digestibility and estimation of endogenous phosphorus losses in growing pigs.

Fermentable fiber may increase endogenous losses of phosphorus (EPL) and amino acids (AA), thereby reducing nutrient digestibility. This study assessed effects of feeding increasing acacia gum with medium-to-high fermentability and low viscosity. Eight barrows cannulated at the terminal ileum were fed a control diet to measure basal endogenous P losses and three diets including 2.5%, 5.0%, or 7.5% acacia gum. Increasing acacia gum quadratically decreased diet ileal digestibility of dry matter (DM), gross energy (GE), linearly decreased diet total tract digestibility of DM, crude protein (CP), GE, and linearly increased hindgut fermentation of DM and GE. Increasing acacia gum linearly increased total tract endogenous P losses. Increasing acacia gum linearly decreased diet total tract digestibility of P, and standardized total tract digestibility of P calculated based on the calculated endogenous P losses or table values (NRC, 2012; 190 mg P/kg DMI). In conclusion, increasing dietary fermentable, low-viscous acacia gum decreased diet ileal and total tract digestibility of DM and GE, but did not affect ileal digestibility of CP and most AA. Increasing acacia gum inclusion reduced total tract digestibility of P, which might have been due to increased specific endogenous losses of P in the total tract of growing pigs.