The study aimed to evaluate the in vitro antioxidant action of glycosaminoglycans (GAGs) from the skin of Oreochromis niloticus, and to determine their ideal concentration to supplement the sperm freezing medium of Prochilodus brevis. In experiment 1, the in vitro antioxidant properties of GAGs were verified through the analysis of DPPH, chelating ferrous ability, and total antioxidant capacity. In experiment 2...