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. 2023 Jan 3:101:skad268.
doi: 10.1093/jas/skad268.

The impact of protein source and grain inclusion on digestibility, fecal metabolites, and fecal microbiome in adult canines

Stephanie D Clark  1 , Clare Hsu  2 , Sydney R McCauley  1 , Maria R C de Godoy  2 , Fei He  2 , Renee M Streeter  1 , Emily G Taylor  1 , Bradley W Quest  1
Affiliations

The impact of protein source and grain inclusion on digestibility, fecal metabolites, and fecal microbiome in adult canines

Stephanie D Clark et al. J Anim Sci. .

Abstract

This study was conducted to determine the effect of animal protein inclusion rate and grain-free or grain-inclusive diets on macronutrient digestibility, fecal characteristics, metabolites, and microbiota in mixed-breed hounds and Beagles. Four experimental extruded kibble diets were made with varying amounts of animal protein and carbohydrates: 1) high animal protein, grain-inclusive (HA-GI), 2) low animal protein, grain-free (LA-GF), 3) low animal protein, grain-inclusive (LA-GI), and 4) high animal protein, grain-free (HA-GF). Thirty-two Beagles and 33 mixed-breed hounds were assigned to 1 of the 4 treatment groups in a completely randomized design that lasted 180 d. All diets were similar in chemical composition and well-digested by the animals. In general, for fecal metabolites, mixed-breed hounds had a greater concentration of total short-chain fatty acid (SCFA) and ammonia and lower indole concentration than Beagles (P < 0.05). In mixed-breed hounds, LA-GF had a greater (P < 0.05) total SCFA concentration than HA-GI and LA-GI; however, this was not observed in Beagles. There were greater concentrations of ammonia, phenol, and indole in HA-GI than in LA-GF (P < 0.05). Breed-affected fecal primary bile acid (BA) concentration, as mixed-breed hounds had a greater concentration of cholic acid (CA) than Beagles (P < 0.05). Mixed-breed hounds fed LA-GF resulted in greater CA concentrations than HA-GI and LA-GI (P < 0.05). Dogs who consumed LA-GF had lower fecal secondary BA content than the other groups (P < 0.05). The distribution of the fecal microbiota community differed in LA-GF compared with the other groups, with lower α-diversity. However, dogs fed LA-GF had the largest difference in composition with greater Selenomonadaceae, Veillonellaceae, Lactobacillaceae, Streptococcus, Ligilactobacillus, Megamonas, Collinsella aerofaciens, and Bifidobacterium sp. than the other groups. A significant breed effect was noted on nutrient digestibility, fecal metabolites, and microbiota. A treatment effect was observed in LA-GF as it resulted in greater fecal SCFA, lower protein fermentative end products, greater fecal primary BAs, lower fecal secondary BA concentrations, and shifts in fecal microbiota.

Keywords: animal-protein; digestibility; fecal microbiome; grain-free; pet food; pulses.

Plain language summary

A recent topic of debate in pet food is whether grain or pulse ingredients and varying amounts of animal-based protein compared to plant proteins are better for pets’ health. Thus, the need to examine ingredients used in pet food is important. This study aimed to evaluate macronutrient digestibility, fecal characteristics, fecal metabolites, and fecal microbiota in both mixed-breed hounds and Beagles when fed extruded diets containing different inclusion rates of animal protein and plant-based ingredients. Four experimental diets were studied 1) high animal protein, grain-inclusive (HA-GI), 2) low animal protein, grain-free (LA-GF), 3) low animal protein, grain-inclusive (LA-GI), and 4) high animal protein, grain-free (HA-GF). We found that all four diets were well-digested by the animals and all dogs remained healthy throughout the study. In addition, LA-GF produced a decrease in alpha diversity, yet was greater in the abundance of Megamonas, which are known to produce short-chain fatty acids. The other diets did not differ significantly. Apparent total tract nutrient digestibility, fecal characteristics, metabolites, and microbiota were affected by breed and dietary treatments. While some have postulated that pulse-rich diets could perhaps be a cause of nutrition-associated dilated cardiomyopathy in canines due to a potentially negative effect on digestibility, our results showed all diets were highly digestible.

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Conflict of interest statement

C. H. and M. R.C. G. have no conflict of interest to declare. B.W.Q., S.R.M, R.M.S., E.G.T., and S.D.C. are employed by BSM Partners LLC.

Figures

Figure 1.
Figure 1.
Principal coordinated plot of unweighted UniFrac distances (A) and nonmetric multidimensional scaling (NMDS) of UniFrac distances (B) of fecal microbial communities of dogs fed experimental diets containing different sources of dietary proteins and carbohydrates.
Figure 2.
Figure 2.
Principal coordinated plot of weighted UniFrac distances (A) and nonmetric multidimensional scaling (NMDS) of UniFrac distances (B) of fecal microbial communities of dogs fed experimental diets containing different sources of dietary proteins and carbohydrates.
Figure 3.
Figure 3.
Principal coordinated plot of Bray–Curtis dissimilarity (A) and nonmetric multidimensional scaling (NMDS) of Bray–Curtis dissimilarity (B) of fecal microbial communities of dogs fed experimental diets containing different sources of dietary proteins and carbohydrates.
Figure 4.
Figure 4.
Fecal microbial α-diversity as (A) observed taxa, (B) Chao 1, and (C) Inversed Simpson diversity of dogs fed experimental diets containing different sources of dietary proteins and carbohydrates after prevalence filtering.
Figure 5.
Figure 5.
Canonical correspondence analysis of taxa abundance.
See this image and copyright information in PMC

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