Effects of dietary polyphenols on inflammatory processes, nutrient digestibility and microbiota in the intestine of piglets
The weaning period of piglets is a stressful event characterized by an increased occurance of enteric infections and a pro-inflammatory intestinal condition with negative effects on feed consumption and animal growth. Recent studies have shown that polyphenolic compounds exert anti-inflammatory effects in the intestine. This study investigated the hypothesis that feeding the polyphenol-rich dietary supplements grape seed and grape marc meal extract (GSGME) or spent hops has the potential to suppress inflammatory processes in the intestine of piglets. Besides, the influence on nutrient digestibility and faecal microbiota composition should be investigated for the first time. A feeding trial with 48 five-week-old piglets was performed. The control group received the basal diet mainly based on wheat, barley and soybean meal; the GSGME group received the diet supplemented with 1% GSGME (AntaOx®, Dr. Eckel GmbH, Niederzissen, Germany) and the hop group received the basal diet supplemented with 1% spent hops (Anta®Phyt H, Dr. Eckel GmbH). Statistical analysis was done by one-way ANOVA. There were no differences in average daily gains, daily feed intake and final body weights between the three groups. However, the gain:feed ratio was increased in the hop group (P < 0.05) and the GSGME group (P = 0.15). Moreover, both treatment groups had lower expression levels of pro-inflammatory genes (e.g. TNFα, IL-1ß and IL-8) and nutrient transporters (SGLT1, GLUT2, GLUT5, PEPT1) in the mucosa of duodenum, ileum and colon (P < 0.05). In line with this, decreased digestibilities of crude protein and crude fiber have been observed in the hop group (P < 0.05). Supplementation of GSGME and hop revealed an increased faecal pH value, lower levels of volatile fatty acids (acetate, propionate, butyrate) together with changes in the faecal microbial composition with a lower amount of Streptococcus spp. and Clostridium cluster XIVa (P < 0.05). In conclusion, this study confirmed the anti-inflammatory effect of polyphenol-rich dietary supplements which can be a useful dietary strategy during weaning. It is suggested, that the improved feed efficiency results from decreased inflammatory processes and might be also due to an interaction with the gut microbiota and their metabolites.
Keywords: grape seed and grape marc meal extract, hop, anti-inflammatory