MICROENCAPSULATION OF BOVINE SPERMATOZOA FOR USE IN ARTIFICIAL-INSEMINATION - A REVIEW

A technique for microencapsulation of bovine spermatozoa has been deve loped with minimal spermatozoal injury and thus of potential use in ar tificial insemination. The polymers poly-l-lysine, polyvinylamine and protamine sulfate have proven best for membranes. Encapsulation has be en successful with capsules ranging in size from 0.75 to 1.5 mm, and w ith sperm concentrations from 45 to 180x10(6) cells mL(-1). Successful extenders include CUE, CAPROGEN, and egg yolk-citrate-glycerol (maxim um 10% v/v egg yolk for normal capsular shape). Capsule fragility (abi lity to rupture under ageing and physical stress) is negatively relate d to membrane thickness which ranges from 1.92 to 5.32 mu m (depending on the concentration of polymer used) and positively related to conce ntration of sperm encapsulated. Heterospermic studies have shown that encapsulated sperm are capable of fertilization in vivo, but are at a disadvantage to unencapsulated sperm when cows are inseminated at conv entional times. Uterine retention of inseminates is favoured by capsul es having a 'sticky' membrane. Using current procedures, preliminary h omospermic fertility studies indicate that sperm encapsulated with pol y-1-lysine or protamine sulfate may achieve normal fertility.