Phytogenic additives are organic molecules that also improve ruminal fermentation, turning the supplemented individuals into more productive animals, without damage the population welfare. The objective of this study was to evaluate the effects of mesquite (Prosopis juliflora [Sw.] DC.) extract as phytogenic additive for sheep finished on pasture in the Brazilian Northeast semiarid region. Twenty-four intact lambs (Santa Ines × Dorper F1 crossbred) were used, with an initial body weight of 23.00 ± 1.83 kg. The experiment was carried out in a complete randomized design with four treatments and six replicates. Treatments consisted of four diets: Pasture and no supplementation; grazing pasture and phytogenic additive; pasture, supplementation with Tifton 85 hay, and concentrate; and pasture, phytogenic additive, and supplementation with Tifton 85 hay and concentrate. Prior to supplementation, animals received the phytogenic additive according to treatment. There were nonsignificant differences for nutrient intake and behavior patterns (P > 0.05). However, additive intake derived from mesquite provided an increase (P < 0.05) in digestibility (14.40% total digestible nutrients), N balance (27.12% retained N:ingested N) and performance (8.82% final body weight, 21.81% total weight gain, and 30.81% average daily gain) compared to animals consuming only pasture in rainy period. Thus, the use of mesquite extract as phytogenic additive is recommended for sheep finished on pasture in the Brazilian semiarid region.

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