Combination of digestibility marker and fiber affect energy and nitrogen digestibility in growing pigs

This study was conducted to investigate if (i) the coefficient of ileal apparent digestibility (CIAD) of gross energy (GE) or nitrogen (N) was influenced by the type of digestibility marker (DMr) and dietary fiber, and (ii) the coefficient of total tract apparent digestibility (CTTAD) of GE or N was influenced by the type of method (i.e. total collection (TC) and DMr) and dietary fiber. Eighteen barrows fitted with a T-cannula at the end of the ileum were used in a 2-period randomized complete block design. Three corn-soybean meal-based diets were formulated with corn starch, corn bran or oat bran at 100 g/kg. All 3 diets contained 3 DMr, which were chromic oxide (Cr), titanium dioxide (Ti), and acid-insoluble ash (AIA). The ileal digesta were collected for 3 days, and the CIAD of GE and N were determined by measuring Cr, Ti or AIA. The feces were collected by using TC method, and the CTTAD of GE and N were determined by using Cr, Ti, AIA, or TC method. There were interactions between diet and DMr (P < 0.001) for CIAD of GE and N and DMr recovery (P < 0.001), and between diet and method for CTTAD of GE and N (P < 0.001). The DMr had similar effect on CIAD of GE and N within each diet, but different effects among the 3 diets. For corn starch and corn bran, the greatest CIAD of GE or N was determined by Ti, while for oat bran, the greatest CIAD was determined by AIA. However, the CTTAD of GE or N of corn starch and the CTTAD of N of corn bran determined by the 3 DMr were not different. The greatest CTTAD of GE of corn bran was determined by Ti or AIA, while the greatest CTTAD of GE or N of oat bran was determined by Cr or AIA. For all 3 diets, the CTTAD of GE and N determined by the TC method was greater (P < 0.001) than those determined by using DMr. The recovery of Ti in feces of pigs fed the oat bran was 78.3%, which was the least among all the 3 diets (P < 0.05). In conclusion, the CIAD of GE or N was more influenced by the choice of DMr compared with CTTAD, and the Ti recovery of pigs fed oat bran was less than corn starch or corn bran.