The potential use of food residues for pet food could significantly contribute to food waste reduction. In the present study, the effects of the inclusion of dried food residues (DFR) (0, 5, 10 and 15%) in a complete diet were evaluated in seven healthy adult cats. At the end of each three-week feeding period, feces were collected. The analysis of the fecal microbiota by 16S rDNA sequencing demonstrated a marked increase of the bacterial alpha-diversity with increasing dietary inclusion levels of DFR. In addition, an increase in the relative abundance of Coriobacteriales, Collinsella and Lachnoclostridum, as well as of propionate and n-valerate in the feces of the cats, was detected. The dietary inclusion of DFR decreased the apparent crude protein digestibility and tended to decrease the apparent crude fat digestibility. Overall, the DFR seemed to be highly fermentable in the intestine of cats, which markedly affected the diversity of the fecal microbiota. As this effect might be critical for a balanced gut microbiota, but also along with the observed depressing effects of DFR on the apparent crude protein and crude fat digestibility, lower inclusion levels are recommended if used as a potential ingredient for cat food in the future.
