Effects of dietary polyphenol-rich grape products on intestinal microflora and gut morphology in broiler chicks

Grapes have high amounts of phenolic compounds, which can modulate the gut activity as well as modify the structure and function of the gastrointestinal tract. The microbiological activity of avoparcin, grape pomace concentrate, and grape seed extract was evaluated in an in vitro study. An in vivo experiment was also conducted to study the effect of the inclusion of grape pomace concentrate and grape seed extract in the diet of broiler chicks on performance, intestinal microflora (by cultured and terminal restriction fragment length polymorphism methodology), and gut morphology at 21 d of age. Dietary treatments included an antibiotic-free diet (CON), a positive control (AVP; 50 mg/kg of avoparcin), and antibiotic-free diets containing grape pomace concentrate (GPC; 60 g/kg) or grape seed extract (GSE; 7.2 g/kg). Performance was not affected by dietary treatment except in the case of birds fed the GSE diet, which showed decreased weight gain. In the ileal content, birds fed CON and GSE diets had the highest populations of Lactobacillus. Compared with the CON diet, the AVP, GPC, and GSE diets increased the populations of Enterococcus and decreased the counts of Clostridium in the ileal content. In the cecal digesta, birds fed GPC and GSE diets had higher populations of Escherichia coli, Lactobacillus, Enterococcus, and Clostridium than birds in any other treatment group. Animals fed GPC and GSE diets showed a higher biodiversity degree than those fed control diets. The frequency of detection of several potential phenol-degrading bacteria as well as unidentified and uncultured organisms was increased in animals fed GPC and GSE diets. Birds fed the CON diet had longer villi and deeper crypt depth than birds in any other treatment group. The highest villi height:crypt depth ratio corresponded to birds fed GPC and AVP diets and the lowest to those fed CON and GSE diets. In conclusion, dietary polyphenol-rich grape products modify the gut morphology and intestinal microflora and increase the biodiversity degree of intestinal bacteria in broiler chicks.