Motility and fertility of alginate encapsulated boar spermatozoa

Ejaculated boar spermatozoa are vulnerable to cold shock. Prolonged storage of boar spermatozoa at low temperatures reduces survival rate, resulting in a bottleneck for the extension of artificial insemination in pig husbandry. This study evaluated whether alginate microencapsulization processing can improve the longevity of boar spermatozoa stored at 5 °C and the fertility of microencapsulated spermatozoa in vivo. Sperm-rich fraction semen from three purebred boars were concentrated and microencapsulated using alginate at 16-18 °C, and then were stored at 5 °C. Following storage for 1, 3 and 7 days, the microcapsule was taken out to assess sperm release under 37 °C incubation with or without 110 rpm stirring. The percentage of sperm released from microcapsules with 110 rpm stirring was higher than without stirring (81 versus 60%) after 24 h of incubation. In another experiment, semen was also microencapsulated to evaluate the sperm motility. The motility of spermatozoa was assessed at 10 min, 8, 24, 32, 48, 56 and 72 h following incubation at 37 °C for nine consecutive days. The fertility of the free and microencapsulated semen was assessed by inseminating sows, and the reproductive traits (conception rate, farrowing rate, and litter size) were recorded. The motility of encapsulated spermatozoa was significantly higher than that of free semen after 8 h incubation at 37 °C after storing for over three days (P < 0.05). No significant difference existed in conception rate, farrowing rate, and litter size between the microencapsulated and non-encapsulated semen after four days of storage. In conclusion, microencapsulation can increase the longevity of boar spermatozoa and may sustain in vivo ova fertilization ability.