The best boar and worst boar were the same in each extender on every day of storage. Many A.I. units can tell interested customers which boars have semen that tends to last longer, although the A.I. units will judge viability on the basis of motility. It is important to realize that a sperm that is not moving is not necessarily dead, and the secretions of the female can stimulate activity in sperm that are not moving. Pooled semen, which combines semen from several boars, does give slightly better pregnancy rates and litter sizes than semen from a single boar. Storage for a long time will cause semen from the weaker boar to die out, leaving predominantly semen from the boars whose sperm naturally live longer.
Packaging affects ease of storage and ease of use.
Semen should be stored in the dark at the temperature the supplier recommends, and gently agitated once every 24 hours to keep sperm well exposed to the extender. Before using semen in any package for insemination, the package should be gently rotated so that all sperm are in the fluid that goes into the sow. Disposable rods should never be reused, and reusable rods should be properly cleaned and stored. Heat detection remains the single most important aspect of a successful A.I. programme. Ideally, detection should be carried out at least once every 12 hours, using a boar.