In vitro digestion and fermentation of animal-derived fermentable substrates using canine and feline faecal inoculum

Abstract

Abstract There is increasing interest in understanding the fermentative benefits of animal-derived fermentable substrates (ADFS) in pet foods. While previous research has assessed various ADFS using faecal inoculum derived from the cat, there is no published literature available for the dog. Additionally, very little is understood of the fermentation profiles of ADFS, such as skin and bone. Therefore, faeces were collected from a cohort of cats and dogs fed a complete and balanced high-protein diet and a selection of substrates were analysed in this study. Individual ADFS (tendon, bone cake, mechanically deboned meat (MDM), corium and hydrolysed collagen (a positive control)) were digested in vitro, followed by fermentation using either canine or feline faecal inoculum. Concentrations of butyrate, indole and ammonia were determined after 24 h of fermentation. Regardless of whether cat or dog faecal inoculum was used, fermentation of hydrolysed collagen produced the highest (P < 0.01) concentrations of butyrate and ammonia and the lowest concentrations of indole. For the other substrates, there were differences in the fermentation profiles between the canine and feline inocula. During the feline faecal fermentations, in comparison to the other substrates bone cake produced high (P < 0.05) butyrate concentrations, whereas in the dog faecal fermentations, MDM resulted in high (P < 0.05) butyrate concentrations. In conclusion, ADFS from different alternative co-products lead to different fermentation products, providing valuable information which may be considered in canine and feline dietary formulations.