Calcium appears to play a role in fertility (and cancer).

Gordon Woods (University of Idaho, USA) said he found this after carrying out studies on cloned mules.

Was told the conference of the American Association for the Advancement of Science.

According to Wood, the vital ingredient in the process of triggering growth in the embryos could have been extra calcium in the surrounding fluid.

He also said that he thinks calcium has a role to play in cancer risk.

Horse red blood cells contained 2.3 times less calcium than human red blood cells.

Levels of calcium in the fluid around the horse blood cell were much higher.

He said that humans are much more prone to cancer than horses (equines).