question: This experiment was carried out in Central Bioterium of Universidade Estadual de Maringá, aiming to evaluate the effect (0, 5, 10, 15 and 20ml/l) of water-administered acetic acid on weaned rats. One hundred and twenty 0f 21-35-days-old Wistar lineage weaned rats, being 60 males and 60 females, distributed in randomized design with 5 treatments and 4 replicates with 6 animal per unit were used in this experiment. Considering the initial experimental period (21-28 days of age) the addition of acetic acid in water affected linearly (p 0.05) the feed conversion, but considering the total experimental period (21-35 days of age) the addition of acetic acid in water did not affect their performance.