LAUSR

Abstract This study assessed the effects of three tannin-based feed additives on the productive performance, foot-pad conditions, plasma metabolome, and caecal microbiota of meat-type chickens. A total of 2,340 male broilers were divided into 4 treatments (9 replicates each) fed either a commercial basal diet (CON) or the basal diet supplemented with one of the three tested products (A, B, or C) up to 49 days. According to manufacturers’ instructions, product A was added to the basal diet at 0.3% from 0 to 49 d, while B and C at 0.13% from 0 to 21 d and 0.12% from 22 to 49 d. Compared to CON, tannin-supplemented birds consumed less feed (6.59 vs. 6.37, 6.49, and 6.35 kg, for CON vs. A, B, and C, respectively; p < .001) and reached a lower slaughter weight (3,599 vs. 3,494, 3,546, and 3,472 g, for CON vs. A, B, and C, respectively; p < .05). Feed conversion ratio (FCR) was not affected by the tannin supplementations, except for the starter phase when CON exhibited lower FCR than the other groups (p < .01). The observed differences in the plasma metabolome between CON and treated groups might indicate an impaired energy metabolism of tannin-supplemented chickens. The significant reduction in the caecal microbial diversity and short-chain fatty acid producer bacteria can also be related to the depressed performance of tannin-fed chickens. In contrast to earlier findings, pododermatitis was unaffected by our treatments. Further dose-response studies can help better exploit tannin-based additives in broiler diets. Highlights Two tannin-based feed additives out of the three tested in this study significantly reduced feed intake and body weight gain of broiler chickens. The tannin-produced shifts in the plasma metabolome and caecal microbiota may have been two reasons for the productive performance depression. Further dose-response trials can help the poultry industry to better elucidate the role of tannins as feed supplements for broiler chickens.