Li, Y. H., Li, F., Liu, M., Yin, J. J., Cheng, B. J., Shi, B. M. and Shan, A. S. 2015. Effect of γ-aminobutyric acid on growth performance, behavior and plasma hormones in weaned pigs. Can. J. Anim. Sci. 95: 165-171. The study was conducted the effects of dietary γ-aminobutyric acid (GABA, 0 and 30 mg kg^-1) on average daily intake, growth performance, behavior and plasma hormone levels in weaned pigs. A total of 96 28-d-old healthy weaned male pigs (Duroc×Landrace×Yorkshire) with similar weight were randomly assigned into two groups. Six units were included in each treatment, with eight pigs in each unit. The trial lasted 35 d. Four pigs were exchanged between every two pens in the same treatment on day 28. No difference was observed on average daily feed intake, average daily gain and feed-to-gain ratio between the pigs fed 30 mg kg^-1 GABA diets and the pigs fed basal diet, respectively. Longer feed consumption time and lower biting incidences were observed in pigs fed GABA, compared with those fed basal diet, respectively. Plasma growth hormone concentration was significantly increased and the plasma concentrations of adrenocorticotrophic hormone and cortisol were lower in weaned pigs in the GABA supplementation group on day 35. Dietary GABA significantly increased the plasma neuropeptide Y concentration on day 14 and day 35. It is indicated that dietary GABA reduced aggressive behavior and regulated endocrine hormones in weaned pigs, ultimately reducing the negative influences of stress (weaning and mixing) on the pigs.