Response of pigs in ileal endogenous amino acid losses to different dietary fiber types determined using the regression method
Dietary fiber, especially fiber with high water holding capacity, is theorized to increase ileal endogenous amino acid (EAA) losses in non-ruminant animals. It is not known whether dietary fiber types have different effects on ileal EAA. Increase in EAA losses would decrease apparent ileal amino acids (AA) digestibility and increase nitrogen excretion into the environment. Information on basal ileal EAA losses in pigs will advance diet formulation on standardized ileal AA digestibility basis. The objective of this study was to evaluate the effect of 2 fiber sources, corn fiber or pectin, on ileal EAA losses in pigs. Total AA, crude protein, and crude fiber contents of corn fiber or pectin used in this study were 9.8, 10.8, and 10.0% or 1.1, 10.8, and 0.2%, respectively. For each fiber type, 3 semi-purified diets were formulated to contain 3 levels of casein (40, 80, and 120 g/kg diet) and 100 g of fiber/kg diet. All fiber within a diet was supplied by either corn fiber or pectin. The experiment consisted of 3 periods of 7 d each with ileal digesta collection on d 6 and 7. Within each period, there were 3 pigs on 3 levels of casein (40, 80, or 120 g/kg diet) in each of 3 blocks per fiber type; and each block served as the experimental unit. There were 18 cannulated pigs with average initial BW of 30, 31, and 30 kg for periods 1, 2, and 3, respectively. Each pig received 3.5% of the starting BW of the smallest pig within each block in 2 equal portions at 0700 and 1800 h. Basal ileal EAA losses were determined from the ordinate intercept, at zero AA intake, of the regression of ileal digesta AA concentration in mg/kg DMI against dietary AA intake in mg/kg DM. Corn fiber resulted in higher (P < 0.05) ileal endogenous His, Leu, and Tyr losses. Isoleucine, Phe, Thr, and Cys showed a tendency (P < 0.1) for higher endogenous loss in pigs fed diets containing corn fiber. In general, the effect of highly-fibrous but low-viscosity corn fiber on ileal endogenous nitrogen and AA losses is similar to that of low-fiber but highly-viscous pectin.
Keywords: corn fiber, endogenous AA, pectin,