Meal composition and Tryptophan/Large Neutral Amino Acids plasmatic ratio in dog

The aim of this study was to assess the impact of meal composition on the plasmatic ratio between Tryptophan (Trp) and 5 other large neutral amino acids (5LNAAs: isoleucine, leucine, valine, tyrosine, phenylalanine). This study included 5 female Labrador Retrievers. Each dog received a meal of puffed rice, minced meat and olive oil (M1) for a single day and then they received a meal of puffed rice and olive oil (M2), with no meat, for another single day. A second meal was administered in the evening to balance the energy intake and both diets were isoenergetic. Blood was collected right before the meal (t0) and after 2, 4, 6, 8 and 10 hours. Trp and phenylalanine concentrations showed no significant difference between M1 and M2 samples. Isoleucine, leucine, valine and tyrosine plasma concentrations were lower after M2. Due to the latter, Trp/5LNAAs ratio was higher after the meal with no meat (M2) at all sampling times (except t0) and such trend reached a statistically significant difference at 2 (median: 0.206 versus 0.311), 4 (median: 0.217 versus 0.345) and 10 (median: 0.242 versus 0.289) hours after the meal. These findings suggest that meal composition has a key role in the Trp bioavailability.