When compared to smaller dogs, large dogs are prone to producing poor quality feces, that could be partially attributed to higher colonic fermentations. Fermentation of undigested proteins could have deleterious effects on the colonic mucosa and affect colonic functions. One of them is water and electrolyte absorption. Highly digestible protein sources, such as wheat gluten, lead to a low protein residue in the colon. The aim of this study was to evaluate the effect of dietary protein source and amount on fecal quality and expression of proteins involved in colonic absorption, as water channel (aquaporin 8; AQP8), and electrolyte channel (Na+/K+ ATPase, as well as cystic fibrosis transmembrane conductance regulator (CFTR)) in the colon of large and small dogs. Eleven female dogs (5 Miniature poodles: MP, 4.9±1.5 kg BW, and 6 German shepherds: GS, 26.6±2.4 kg BW) were used. Two diets varying in protein source and level were tested in a crossover study. Diets were isoenergetic with similar fat, TDF and ash content. Main protein sources and levels were wheat gluten meal at low protein level (LP; CP=21.4% as fed) and poultry meal at high protein level (HP; CP=34.8% as fed). The study design comprised two 14-d experimental periods and a 24-d washout period. Feces were scored (1=dry feces to 5=liquid diarrhea) daily for 7 days. Biopsies from proximal and distal segments of the colon were performed at the end of each experimental period. mRNA expression of two variants of AQP8 (AQP8v1 and AQP8v2), Na+/K+ ATPase and CFTR were measured by RT-real time PCR by comparison with GAPdH expression. Fecal score data were analyzed using Kruskal Wallis test and gene expression data were normalized and analyzed with repeated measures ANOVA. Fecal score was higher in GS than MP dogs whatever the diet (p<0.001 for LP and p<0.01 for HP) and in HP fed dogs whatever the breed (p<0.05 for MP and p<0.01 for GS). A trend for higher mRNA expression of AQP8v1 was found in MP, compared with GS dogs, when fed HP diet (p<0.09). A trend for higher expression in the distal colon, associated with a breed effect was also observed (p=0.15). Similarly an effect of [breed*biopsy location] was observed in AQP8v2 expression in dogs fed HP (p<0.09); expression was higher in the distal colon of MP dogs. mRNA expression of AQP8v1 and AQP8v2 was constant in GS dogs. No effect of diet, breed or biopsy location was found for Na+/K+ ATPase nor CFTR expression. Poorer fecal score in large compared to small dogs could be partially attributed to lower water channels mRNA expression in the distal colon. This divergence between the two breeds appeared to decrease when feeding highly digestible protein at low level. To improve fecal score in large sensitive dogs modulation of protein source and content could therefore be an adequate nutritional strategy.
Influence of Dietary Protein Source and Content on Fecal Quality and Gene Expression of Water and Electrolyte Transporters of Colon in Miniature Poodles and German Shepherds
VENDA DA GRACA NERY, JOANA MARIA;
2009-01-01
Abstract
When compared to smaller dogs, large dogs are prone to producing poor quality feces, that could be partially attributed to higher colonic fermentations. Fermentation of undigested proteins could have deleterious effects on the colonic mucosa and affect colonic functions. One of them is water and electrolyte absorption. Highly digestible protein sources, such as wheat gluten, lead to a low protein residue in the colon. The aim of this study was to evaluate the effect of dietary protein source and amount on fecal quality and expression of proteins involved in colonic absorption, as water channel (aquaporin 8; AQP8), and electrolyte channel (Na+/K+ ATPase, as well as cystic fibrosis transmembrane conductance regulator (CFTR)) in the colon of large and small dogs. Eleven female dogs (5 Miniature poodles: MP, 4.9±1.5 kg BW, and 6 German shepherds: GS, 26.6±2.4 kg BW) were used. Two diets varying in protein source and level were tested in a crossover study. Diets were isoenergetic with similar fat, TDF and ash content. Main protein sources and levels were wheat gluten meal at low protein level (LP; CP=21.4% as fed) and poultry meal at high protein level (HP; CP=34.8% as fed). The study design comprised two 14-d experimental periods and a 24-d washout period. Feces were scored (1=dry feces to 5=liquid diarrhea) daily for 7 days. Biopsies from proximal and distal segments of the colon were performed at the end of each experimental period. mRNA expression of two variants of AQP8 (AQP8v1 and AQP8v2), Na+/K+ ATPase and CFTR were measured by RT-real time PCR by comparison with GAPdH expression. Fecal score data were analyzed using Kruskal Wallis test and gene expression data were normalized and analyzed with repeated measures ANOVA. Fecal score was higher in GS than MP dogs whatever the diet (p<0.001 for LP and p<0.01 for HP) and in HP fed dogs whatever the breed (p<0.05 for MP and p<0.01 for GS). A trend for higher mRNA expression of AQP8v1 was found in MP, compared with GS dogs, when fed HP diet (p<0.09). A trend for higher expression in the distal colon, associated with a breed effect was also observed (p=0.15). Similarly an effect of [breed*biopsy location] was observed in AQP8v2 expression in dogs fed HP (p<0.09); expression was higher in the distal colon of MP dogs. mRNA expression of AQP8v1 and AQP8v2 was constant in GS dogs. No effect of diet, breed or biopsy location was found for Na+/K+ ATPase nor CFTR expression. Poorer fecal score in large compared to small dogs could be partially attributed to lower water channels mRNA expression in the distal colon. This divergence between the two breeds appeared to decrease when feeding highly digestible protein at low level. To improve fecal score in large sensitive dogs modulation of protein source and content could therefore be an adequate nutritional strategy.
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