Sydney Morning Herald
November 11, 2004

Mission of mercy to save rhinos
by Deborah Smith

Will it be a girl or a boy? For rhinos and elephants, the question could soon be obsolete.

Sydney scientists have begun a world-first project to separate rhino and elephant semen into male and female sperm so breeding programs can choose the sex of the offspring most needed to increase the endangered animals’ members.

Chis Maxwell, associate dean of veterinary science at the University of Sidney, said female rhinos were in short supply. For unknown reasons, about 75 percent of rhino calves born in captive breeding programs are males. “We don’t know if it is a reflection of good or bad management, but it is a problem,” Professor Maxwell said.

Male rhinos were more difficult to manage than females and large numbers of them living together did not reflect conditions in the wild. Female rhinos, like female elephants, are preferred for breeding purposes.

The University of Sidney team produced the world’s first sperm-sorted lamb- a male called Larry- in 1995. The technique has since been used for other domestic animals, including cattle, pigs and horses.

The scientists collected rhino semen from two white and three black rhinos at the Western Plains Zoo in Dubbo this week.

While the delicate procedure, using electrical stimulation, required the rhino to be fully anaesthetized, an Asian elephant at Melbourne Zoo is being trained to produce his samples for science by ejaculating into a special collection device.

Professor Maxwell said elephant and rhino sperm were no bigger than sperm from other animals. “All sperm are about the same size. You need a microscope to see them.”

The sperm-sorting technique, however, relies on “female” sperm, which carry an X chromosome, having a larger amount of DNA than the “male” sperm, that carry a Y chromosome.

A florescent dye that binds to the DNA is added to the sperm. The female sperm, with more DNA, give off more light than the male sperm and the two are separated on this basis in an instrument called a flow cytometer, and then collected in blue and pink tubes.

The project adapting the method to rhino and elephant sperm is backed by XY Inc., an American company with rights to the sperm sorting technique.