Four concentrations (0, 200, 400, 600 and 800 mg extract per ml of water) of mesquite extract were used as phytogenic additive to verify the potential to increase the nutritional value of the feed, ruminal parameters (primarily propionate production) and nitrogen use efficiency, microbial protein synthesis and quantify the reduction of ciliated protozoa and characterize the ingestive behavior of sheep. Ten adult male sheep were subjected to a 5 × 5 double Latin square design. Prior to feeding, the animals received the mesquite extract. Nutrient intake was estimated from the difference of the amount of feed provided and the total surplus. Rumen content samples were collected to evaluate the profile of short-chain fatty acids, ammonia nitrogen, pH, ciliated protozoa, turnover rate and disappearance rate. To estimate the microbial protein synthesis, the technique of purine derivatives was used. The mesquite extract quadratically increased (P < 0.05) the digestibility of dry matter, organic matter, crude protein and total digestible nutrients, as well as increased propionate production, acetate:propionate ratio and microbial protein synthesis. The numbers of ciliate protozoa in the rumen decreased as a result of mesquite extract inclusion in the diet. The use of mesquite pod extract at a concentration of 488 mg/mL is recommended to improve digestibility of dry matter, organic matter, crude protein and total digestible nutrients, and to optimize microbial protein synthesis and increase propionic acid production.