Intake, Digestibility, Nitrogen Balance, Rumen, and Blood Parameters of Cattle Supplemented With Acacia mearnsii Extract

This study aimed to evaluate the effect of increasing levels of Acacia mearnsii extract as a source of condensed tannins on feed intake, nutrient digestibility, nitrogen (N) balance, rumen fermentation, and blood parameters of feedlot‐finished cattle. Eight rumen‐cannulated bulls were distributed in a replicated 4 × 4 square Latin design. The treatments consisted of a control diet with no extract inclusion (0 g/kg) and three diets with 10, 30, and 50 g/kg on a dry matter (DM) basis of A. mearnsii extract. Adding A. mearnsii extract to the diet linearly reduced ( p < 0.05) the intake of DM, crude protein (CP), extract ether (EE), neutral detergent fiber (NDF), non‐fiber carbohydrate (NFC), and total digestible nutrient (TDN); however, it linearly increased ( p < 0.05) the digestibility of DM, NDF, and NFC. Including extract in the diet linearly reduced N‐intake and N‐urinary excretion and increased quadratically fecal N excretion ( p < 0.05). Ruminal ammonia nitrogen (RAN) concentration and short‐chain fatty acids were not affected ( p > 0.05), but ruminal pH and serum proteins linearly decreased ( p < 0.05) with the inclusion of extract. Including A. mearnsii extract in the diet of cattle at levels up to 50‐g/kg DM reduces intake and increases the utilization of the feed and its nutrients.