Potential and challenges of tannins as an alternative to in-feed antibiotics for farm animal production

Huang, Qianqian; Liu, Xiuli; Zhao, Guoqi; Hu, Tianming; Wang, Yuxi

Extracts of grape (Vitis vinifera) seed and grape pomace contain significant amount of polyphenolic compounds including CT (Prieur et al., 1994; Choy et al., 2014) , which have been assessed for their uses as natural feed additives to monogastric food producing animals. Choy et al. (2014) reported that adding 1% of grape seed extract to pig diets increased abundances of Lachnospiraceae, Clostridales, Lactobacillus and Ruminococcaceae in fecal microbiome. They found that oligomers (dimerepentamer) of grape tannin were only partially metabolized by the gut microbiota, producing phenolic metabolites that are known to be more readily absorbed. These phenolic compounds may have contributed to the altered bacterial populations thereby exerted the beneficial effects on the colon. Wang et al. (2008) found that CT in grape seed extract at the dietary concentrations from 5 to 80 mg/kg significantly decreased fecal shedding of E. tenella, improved antioxidant status, reduced mortality and increased growth performance of E. tenella infected broiler chicken and the most favorable results were observed with diets containing 10 to 20 mg CT/kg DM. Farahat et al. (2017) showed that grape seed extract possessed significant antioxidant and immunostimulant effects when fed to broiler chickens at the dietary concentrations of 0.125% to 2% with 0.125% to 0.25% being the optimum dosages. Further increasing the concentration negatively affected birds' growth performance, protein and amino acid digestion (Chamorro et al., 2013) .