Effect of the form of dietary fat and the concentration of dietary neutral detergent fiber on ileal and total tract endogenous losses and apparent and true digestibility of fat by growing pigs

An experiment was conducted to determine the effect of the form of dietary fat (extracted or intact fat) and of dietary NDF on ileal and total tract endogenous losses of fat (ELF), on apparent ileal (AID) and apparent total tract digestibility (ATTD) of fat, and on true ileal (TID) and true total tract digestibility (TTTD) of fat in growing pigs. A cornstarch-based basal diet that contained 1.27% fat was prepared and 3 diets were formulated by adding 2.0, 4.0, or 6.0% extracted fat (corn oil) to the basal diet at the expense of cornstarch. Three additional diets were formulated by adding 3.1, 6.2, or 9.3% Solka-Floc (International Fiber Corp., North Tonawanda, NY) to the diet containing 4.0% corn oil at the expense of cornstarch. The remaining 4 diets were prepared by adding whole corn germ meal to the diet at the expense of defatted corn germ meal to contain 3.0, 6.0, or 9.0% intact fat. Solka-Floc was also included in this diet at the expense of cornstarch in an attempt to keep NDF constant. Eleven barrows (initial average BW of 38.1 ± 1.3 kg) were fitted with a T-cannula in the distal ileum, allotted to the 11 diets in an 11 x 11 Latin square design, and fed the diets at 3 times the energy requirement for maintenance. Increasing dietary extracted fat increased (linear and quadratic, P < 0.001) the AID and ATTD of fat. Increasing dietary intact fat also increased (linear and quadratic, P < 0.05) the AID and ATTD of fat. The average apparent digestibility of extracted fat (81.9%) was greater (P < 0.001) than that of intact fat (63.2%). Estimates of ELF were smaller (P < 0.05) for extracted fat than for intact fat at the end of the ileum and over the entire intestinal tract, but the TID (93.8%) and TTTD (94.2%) of extracted fat were greater (P < 0.05) than the TID (78.6%) and TTTD (84.1%) of intact fat. Increasing dietary extracted fat had no effects on the TID and TTTD of fat, but increasing dietary intact fat resulted in a quadratic reduction (P < 0.05) in the TTTD of fat. Increasing dietary NDF had a quadratic effect (P < 0.05) on the ATTD of fat but did not influence the AID, TID, and TTTD of fat. In conclusion, extracted fat induces a smaller amount of ELF and has a greater apparent and true digestibility than intact fat at the end of the ileum and over the entire intestinal tract. Purified NDF has little influence on apparent and true digestibility of fat.