Sex should be the only way of procreation...

But free sex often created errors. And - as farmers want improved quality in their stocks - it would be rather problematic to transport one-tonne bulls just to offer them pleasure...

That's why cattle and pig sperm make the trip to the uterus independently of the testicles in which they develop because chemical additives exist to make them both last longer.

But, by now, the ram sperm cannot do it. It stays alive for only six to ten hours after ejaculation, so a stud ram from England won't father Australian ewes without direct contact. To make the situation more complicated, the foot-and-mouth disease outbreak in Britain five years ago made the agriculture ministry in Great Britain to ban the transport of farm animals over large distances.

But some rams carry valuable genes, e.g. Genes resistant to scrapie, a sheep disease similar to mad cow (bovine spongiform encephalopathy) which should be spread in livestocks.

Artificial-insemination companies would be also interested in expanding their markets, too. Dr. Rhiannon Lloyd and Dr. Bill Holt, of the Institute of Zoology in London, had to solve out the problem. Frozen semen is not a satisfactory solution. Ewes have cervixes shaped in a way that makes it impossible for a bendy tube to reach the uterus via the traditional route and thawed semen would be injected directly into the uterus through the ewe's belly wall, which is costly and traumatic for the animal.

The researchers are seeking for the natural mechanisms of the species with naturally long-lived sperm.

Female bats maintain viable sperm inside themselves for months and many mammals store sperm during winter: they mate in autumn, store the sperm and fecundate the eggs in spring, when the female gets the resources to grow embryos. So do many fish, newts and lizards, whose females store the sperm of one mating for many clutches.

Once a female shark gave birth after six years in captivity!

Till now, the researchers have found a promising mixture of proteins, with the unwieldy name of sAPM, which can prolong the life of ram sperm by several hours, and they intend to improve the mix.