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Several factors may influence the amount of protein that reaches the colon after feeding, such as the amount of DM ingested and content and digestibility of protein sources included in the diet. Therefore, the use of highly digestible protein sources results in less flow of protein residues in the large intestine and a possible reduction in production of fermentation metabolites and flatulence in dogs(1,2).
Although digestion and absorption of proteins in the small intestine are efficient processes, substantial amounts of undigested proteins are directed to the large intestine(3,4), where the microbial fermentation of these components results in the production of various putrefaction compounds, such as ammonia, phenols, indoles, SCFA, branched-chain fatty acids, gases (H2, CO2 and methane), biogenic amines (putrescine, cadaverine, histamine, phenylethylamine) and lactate. Some of these compounds influence faecal odour and can be toxic if produced in high concentrations(5,6). Moreover, according to Zentek et al.(7), the ingestion of diets with high concentrations of proteins favours the growth of undesirable bacteria, such as Clostridium perfringens, and decreases the faecal counts of other beneficial bacteria, resulting in imbalance in the intestinal microbiota and consequent increase in excretion of enterotoxins and other metabolic products related to the increase of the protein decomposition in the colon.
Brachycephalic dog breeds such as French bulldogs have been identified as having faeces with a stronger odour and higher frequency of flatulence. Their typical anatomical characteristics result in aerophagia, predisposing to increased gas production. This gas production is associated with a higher presence of non-assimilated substrates, resulting in flatulence and foul-smelling faeces(8,9). Degradation of undigested proteins in the colon may be responsible for the strong faecal odour in brachycephalic dogs. Therefore, nutritional strategies based on sources and altered concentrations of protein may be important in reducing the impact of fermentative activity in the colon and thus modulate the composition of the intestinal microbiota. Its metabolic activity and the formation of fermentation products are effects that can be important for the reduction of strong faecal odour in brachycephalic dogs. Zentek(10)reported that dogs fed with higher...