Abstract
Grain based ingredients are replaced in part by pulse ingredients in grain-free pet foods. Pulse ingredients are lower in methionine and cysteine, amino acid (AA) precursors to taurine synthesis in dogs. While recent work has investigated plasma and whole blood taurine concentrations when feeding grain-free diets, supplementation of a grain-free diet with various nutrients involved in the biosynthesis of taurine has not been evaluated. This study aimed to investigate the effects of supplementing a complete grain-free dry dog food with either methionine (MET), taurine (TAU), or methyl donors (choline) and methyl receivers (creatine and carnitine; CCC) on postprandial AA concentrations. Eight healthy Beagle dogs were fed 1 of 3 treatments or the control grain-free diet (CON) for 7 d in a 4 × 4 Latin square design. On d7, cephalic catheters were placed and one fasted sample (0 min) and a series of 9 post-meal blood samples were collected at 15, 30, 60, 90, 120, 180, 240, 300 and 360 min. Data were analyzed as repeated measures using the PROC GLIMMIX function in SAS (Version 9.4). Dogs fed MET had greater plasma and whole blood methionine concentrations from 30 - 360 min after a meal (P < 0.0001) and greater plasma homocysteine concentrations from 60 - 360 min after a meal (P < 0.0001) compared to dogs fed CON, TAU and CCC. Dogs fed TAU had greater plasma taurine concentrations over time compared to dogs fed CON (P = 0.02), but were not different than dogs fed MET and CCC (P > 0.05). In addition, most AA remained significantly elevated at 6 h post-meal compared to fasted samples across all treatments. Supplementation of creatine, carnitine and choline in grain-free diets may play a role in sparing the methionine requirement without increasing homocysteine concentrations. Supplementing these nutrients could also aid in the treatment of disease that causes metabolic or oxidative stress, including cardiac disease in dogs, but future research is required.