The effects of supplemental brewers yeast on postprandial amino acid concentrations in healthy adult sled dogs

Yeast has been used in animal systems to modulate the immune response and support gut health. Certain amino acids (AA) are reported to also exert positive effects on the gut, supporting the intestinal barrier and restoring mucosal immune homeostasis. The objective of this study was to evaluate the effects of brewers yeast on postprandial serum AA appearance in dogs. Nineteen privately owned domestic Siberian huskies and 1 Alaskan husky (9 females: 5 intact, 4 spayed; 11 males: 3 intact, 8 neutered), with an average age of 4.8 ± 2.6 yr and body weight (BW) of 25.6 ± 4.1 kg, were enrolled in this study. Ten dogs received a dry extruded control diet (Ctl) and 10 the Ctl diet top-dressed with yeast to receive a daily ß-glucan dose of 7 mg/kg BW (treatment, Trt) for 10 wk. At weeks -1, 2, 4, and 8 postprandial free AA concentrations were quantified. A fasted blood sample was collected, a meal was provided, followed by further blood sampling 1, 2, and 4 h post-meal. Serum IL-10 concentrations were analyzed from the fasted sample. All data were analyzed using PROC GLIMMIX of SAS, with dog as a random effect and week, diet group, and sampling time point as fixed effects for AA, and with dog as a random effect and week as a fixed effect and repeated measure for IL-10. There was no effect of treatment on any AA, though a significant Trt*wk*timepoint interaction effect was observed for His and Trp (P ≤ 0.05). An overall increase was observed in many AAs for all dogs-serum concentrations of Lys, Met, Thr, Trp, Ala, Arg, Gln, Gly, Pro, Ser, Tau, and Tyr were greatest at week 8 in all dogs when compared to concentrations at week -1 (P ≤ 0.05). Serum IL-10 concentrations did not differ by week or between groups (P > 0.05). In 3 Trt dogs that had greater gut permeability than all other dogs at week -2, as reported in a previous publication, serum Ile, Thr, and Val concentrations were greater at week 8 compared to week -1 (P ≤ 0.05) and Leu concentrations were greater 1 and 2 h postprandial at week 8 compared to the same time points at week -1 (P ≤ 0.05). The results of this study suggest that supplemental yeast may have a beneficial effect on peripheral AA availability without impacting inflammatory status in dogs. Future studies should seek to investigate the effects of reducing or improving gut permeability with yeast on nutrient digestive and metabolic efficiencies or consider yeast in clinical nutrition to support dogs with gastrointestinal diseases.