Detection of a protein from the sperm of infertile bulls may help create an objective test for human male infertility, a University of Missouri scientist says.

The protein ubiquitin appears to be a marker of semen abnormalities. If this is so, we hold have a truly objective test for male infertility.

Ubiquitin is found inside al mammalian cells, and has been found on the surface of defective sperm cells from bulls and stallions as well as men. On the surface, it appears to indicate structural abnormalities and contamination with immature sperm-precursor cells.