PSIX-2 - Effects of diets supplemented with bioactive peptides on nutrient digestibility, immune cell responsiveness, and fecal characteristics, microbiota, and metabolites of adult cats

Abstract: Bioactive peptides (BP) are recognized for their ability to function as antioxidants and maintain lipid stability. They may have positive health effects, including antihypertensive, anti-inflammatory, antimicrobial, osteoprotective, gut health and immunomodulatory properties. Our objective was to determine the apparent total tract digestibility (ATTD) of bioactive peptide-containing kibble diets and assess how the fecal characteristics, metabolites, and microbiota were affected in adult cats. All procedures were approved by the University of Illinois IACUC. Twelve adult cats (4-5 yr; 4.84 kg avg. BW) were used in a replicated 4x4 Latin square design (n=12/group) and fed to maintain BW. In each experimental period, cats were allotted to one of four extruded kibble experimental diets: control (4% dried chicken), chicken (4% chicken BP), marine1 (2% marine BP), and marine2 (4% marine BP). Health was confirmed by baseline serum chemistry and complete blood count analysis. Each experimental period lasted 28 days, with a 20-day adaptation phase, 5 day fecal collection [for nutrient digestibility, microbiota, metabolites, IgA, calprotectin, lactoferrin, pH, and dry matter (DM) analysis], 2 day blood collection (for serum chemistry, complete blood count, and immune cell functionality analysis), and 1 day for transport stress testing. For transport stress, cats were transported in a vehicle in individual carriers for 45 minutes. Upon return, their behavior was evaluated using the cat stress score (CSS). Saliva samples were collected within 15 minutes to measure cortisol concentrations and blood samples were collected after 3 hours to measure concentrations of oxidative stress markers [superoxide dismutase (SOD) and malondialdehyde (MDA)] and inflammatory cytokines. Fecal microbiota data were evaluated using QIIME2. All other data were analyzed using the Mixed Models procedure of SAS, with P< 0.05 being considered significant. No significant differences were observed in animal health outcomes, with all cats remaining healthy within reference ranges. There were no differences in fecal characteristics, metabolites, and microbiota diversity. Cats fed the marine2 diet had a 3.61% higher (P< 0.05) ATTD of DM and a 2.5% higher organic matter digestibility than those fed the control diet. The relative abundance of fecal Blautia was higher (P< 0.05) in cats fed the control diet than those fed the chicken diet, while relative abundance of fecal Slackia was higher (P< 0.05) in cats fed the control diet than those fed the chicken or marine1 diets. In comparison to cats fed the marine1 diet, the relative abundances of fecal Sellimonas and Bifidobacterium were lower (P< 0.05) in cats fed the control diet. Neither transport stress nor diet impacted the oxidative stress markers, cytokines, cortisol, or CSS. Furthermore, the diet did not affect immune cell functionality. In conclusion, including BP, in particular marine2 at 4% inclusion, to feline diets may increase nutrient digestibility and modify fecal microbiota.