PSIX-15 - The effects of torula yeast as a protein source on digestibility, inflammation, and gut microbiome in Labrador Retrievers with chronically poor stool quality.

Abstract: Four Rivers Kennel examined the effects of varying protein sources on digestibility, inflammation, and gut microbiota in Labrador Retrievers with historically poor stool quality. Thirty dogs (15 male, 15 female; ages 3 – 10 years) with stool quality scores ≤ 2.5 on a 5 pt scale were randomly assigned to 1 of 3 diets meeting AAFCO requirements with differing protein sources and similar nutrient profiles: 1) chicken meal (PC); 2) 10% brewer’s yeast (BY); 3) 10% torula yeast (TY; SylPro, Arbiom, Durham, NC). Another 10 dogs (5 male, 5 female) with normal stool quality (score ≥ 3) received diet 1 and served as negative control (NC). After 7 days acclimation to diet 1, dogs began treatments. Daily stool scores and weekly body weights were recorded. On days 7, 21, and 36, blood serum was analyzed for c-reactive protein (CRP), and feces for S100A12, alpha-1 proteinase inhibitor (a1PI), calprotectin, and microbiota dysbiosis index (MDI). Apparent total tract digestibility was assessed using the indicator method with 2g titanium dioxide administered orally via gel capsules. Statistical analysis was performed by repeated measures model in SAS for stool scores, body weight, biomarkers, and microbiota or by one-way ANOVA in JMP for digestibility coefficients. Stool scores were greater in NC (P < 0.01), changed daily in all groups (P < 0.01) without noticeable overall trends, and were not affected by treatment*day interaction (P = 0.64). Body weight was greater (P = 0.01) and CRP lower (P < 0.01) in NC dogs than poor stool dogs. Dry matter and carbohydrate digestibility did not differ between groups (P ≥ 0.14). NC dogs had greater fat digestibility compared to BY dogs (94.64 ± 1.33 % vs 91.65 ± 1.25%; P = 0.02). Protein digestibility was reduced in PC (58.91 ± 4.68%) and BY (58.26 ± 4.42%) compared to NC (75.52 ± 5.01 %), but TY diet improved protein digestibility to levels similar to NC (72.18 ± 5.01%, P = 0.03). There were no treatment effects on S100A12 or a1PI (P ≥ 0.44). Calprotectin decreased at a greater rate overtime in TY dogs (P < 0.01). There was a treatment*day interaction for MDI: BY and TY fluctuated less overtime (P = 0.01). Blautia (P = 0.03) and Clostridium hiranonis (P = 0.05) abundances were reduced in BY and TY. Dogs never exhibited significant dysbiosis (MDI < 2), and bacterial abundances remained within normal ranges. Dogs with chronically poor stool quality experience reduced body weights, increased serum CRP, and altered nutrient digestibility, but TY helped improve protein and fat digestibility, sustain microbiome, and reduce fecal calprotectin. Feeding torula yeast long-term may help improve plane of nutrition to better maintain weight and reduce inflammation in dogs with chronically poor stool quality.