Effect of age and method on ileal endogenous amino acid flow in turkey poults

Ileal endogenous amino acid (IEAA) flow in turkey poults was determined at 2 experimental locations on d 5,15, and 21 posthatch using 3 methods, namely a N-free diet (NFD), a highly digestible protein (casein), and the regression method, obtained by regressing IEAA flow against dietary casein levels. The diets were semipurified and contained 0, 50, 100, or 150 g of casein/kg of diet as the sole source of dietary protein. Each diet was fed for 5 d to 6 replicate cages of 30 (d 5), 10 (d 15), or 8 (d 21) birds per cage. There was no interaction between locations and age or locations and diet, so the data from both locations were pooled. Real endogenous amino acid flow on d 5 (NFD method) was higher (P < 0.05) than on d 15 or 21. Real endogenous amino acid flow estimated from the NFD and the regression methods was different on d 5 (P < 0.05), but there were no differences in IEAA flow for most of the amino acids on d 15 and 21. Increasing the level of casein resulted in a linear (P < 0.05) increase in IEAA flow. The amino acids with the lowest flow were Trp and Met, whereas Glu had the greatest flow. The results obtained from this study indicate that data generated across laboratories were repeatable. The results also suggest that about twice as much amino acids of endogenous origin are found in the digesta of poults on d 5 relative to d 21. Also, as poults age, there is a decrease in IEAA flow from d 5 to 15, but flows from d 15 to 21 are not different. These observations suggest that apparent digestibility coefficients for poults on d 5 and d 15 or 21 could be significantly influenced by the level of endogenous amino acids, more so on d 5.