The present study assessed the effect of dietary supplementation of pomegranate peel (methanolic) extract (PPE) on the nutrient digestibility, faecal fermentative metabolites and antioxidant status of dogs. Six medium-sized dogs of mixed breeds were allocated to two groups in a replicated cross-over design and fed a basal diet with and without supplementation of PPE at 50 mg/kg body weight. Each of the experimental periods consisted of 30 d, with a 21 d washout period in between. Results indicated that PPE supplementation led to no significant changes in nutrient digestibility except a trend of improvement (P = 0·070) in crude fibre digestibility. PPE supplementation significantly (P < 0·001) influenced faecal pH, ammonia and lactate production, indicative of positive effects of PPE polyphenols. PPE supplementation further increased faecal SCFA concentration accompanied by a reduction (P < 0·01) in branched-chain fatty acids. PPE supplementation also improved (P < 0·05) indices of erythrocytic antioxidants, namely reduced glutathione, catalase, glutathione peroxidase and glutathione S-transferase together with an improvement in lipid peroxidation. Overall, it can be concluded that dietary supplementation with PPE at 50 mg/kg body weight had a positive impact on hindgut fermentation and antioxidant status in dogs, thereby demonstrating its potential as a gut health-promoting nutraceutical.

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BACKGROUND: This in vitro study aimed to compare the hindgut fermentability and digestibility of four different sources of polyphenols, namely orange (Citrus sinensis) peel (ORP), pomegranate (Punica granatum) peel (PMP), Indian blackberry (Syzygium cumini) pulp (IBP), and Jerusalem artichoke (Helianthus tuberosus) tuber (JAT), and their influence on the viability of a canine-origin probiotic, Lactobacillus johnsonii CPN23.RESULTS: An in vitro gas production test carried out using the four substrates for a period of 72 h with dog faecal inoculum indicated that the total gas production, dry matter, and organic matter digestibility were significantly (P < 0.001) higher with JAT, whereas they were lowest for PMP. Short-chain fatty acids production was significantly higher (P < 0.001) with ORP and JAT, with the least values recorded for PMP. The ammonia-nitrogen production was significantly (P < 0.001) higher with JAT than with ORP, IBP, and PMP, and a lower (P < 0.001) pH was evident with ORP, JAT, and IBP than with PMP. Viability of L. johnsonii CPN23 was tested in the presence of the polyphenol-rich extract from each of the four sources at varying doses (50, 500, 1000, 2500, and 5000 ∼g mL −1 ). PMP extract showed the highest inhibitory effect on the probiotic bacteria's growth in a dose-and time-dependent manner (P < 0.001). ORP and IBP extracts were stimulatory at the optimum dosage, whereas JAT reduced probiotic activity significantly at all doses tested. CONCLUSION: Overall, the results indicate a higher hindgut fermentability of JAT, ORP, and IBP, suggesting their potential beneficial effects for gut health application. An interaction study between polyphenol extract and L. johnsonii CPN23 showed a stimulatory effect of polyphenolic extracts from ORP and IBP on probiotic growth at optimal dosage. Consistent with the fermentation study findings, PMP extract reduced the growth of L. johnsonii CPN23 irrespective of the doses tested.