A boar sperm encapsulation technology in barium alginate has been developed to enhance reproductive performances and spermatozoa preservation time; aim of this work was to evaluate the effect of in vitro sperm encapsulation on polyspermy as a function of storage time at 18 degrees C. A total number of 40 in vitro fertilization (IVF) tests were performed using encapsulated or diluted spermatozoa (20 IVF each treatment). Overall, 1288 in vitro matured oocytes were fertilized with spermatozoa stored at 24, 48 or 72 h at 18 degrees C for both treatments polyspermy and normospermy, and the non-penetration rates were assessed by optical microscopy. Results indicate a significant reduction in risk of polyspermic oocytes when spermatozoa are preserved in barium alginate membranes (incidence risk ratio: 0.766 with respect to diluted); such enhancement could be explained by lesser damage of sperm membranes achieved by encapsulation technology.