Microencapsulation of canine sperm and its preservation at 4 °C

Abstract

The objective of this study was to develop a preservation method for canine sperm using microencapsulation. Pooled ejaculates from three beagles ( Canis familiaris) were extended in egg yolk Tris extender and were encapsulated in gel (alginate only) or polycation (poly- l-lysine membrane bound) microcapsules at 0.75% and 1.0% alginate concentration. In Experiment 1, characteristics of microcapsule and microencapsulated sperm were evaluated during chilling storage for 48 h. Gel microcapsules at 0.75% alginate concentration had a teardrop-like structure with fragility, whereas those at 1.0% alginate had a solid spherical structure. In all groups, diameter of the microcapsules increased with duration of storage (P < 0.05). Alginate concentration did not affect the sperm recovery rate from microcapsules. Total average recovery rate of sperm from polycation microcapsules was lower than that of gel microcapsules (P < 0.05). Progressive motility of polycation microencapsulated sperm and unencapsulated sperm (control) was higher than that of the gel microencapsulated sperm, both at 0.75% and 1.0% alginate concentration (P < 0.05), although viability of sperm was similar among the three groups. In Experiment 2, to evaluate the sperm longevity after chilling storage, sperm were microencapsulated in polycation microcapsules at 1.0% alginate concentration, stored at 4 °C for 0, 1, 4, and 7 d, and then cultured at 38.5 °C for 0, 6, and 24 h. Progressive motility and viability of microencapsulated sperm were higher than those of unencapsulated spermatozoa at 0 to 24 h of culture after 4 and 7 d of chilling storage (P < 0.05). In conclusion, polycation microencapsulation at 1.0% alginate concentration can be successfully applied for chilling storage of canine sperm by maintaining motility and viability for up to 7 d.