Sperm-sorting technology that could allow livestock producers to predetermine the sex of their animals has been significantly improved by the United States Department of Agriculture scientists who developed the original technology.
Animal physiologist Lawrence Johnson developed the patented sperm sexing technology a decade ago. The method separates living female-producing X-chromosome sperm from male-producing Y-chromosome sperm based on their DNA.
In the past year, Johnson and colleagues have improved the rate of sexed sperm production by 15 to 20 fold, enhancing sexed sperm’s adaptability for livestock reproduction worldwide.
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The technology uses a fluorescent dye that sticks to sperm based on how much DNA the sperm contain. The female X-chromosome sperm contain about four percent more DNA and therefore hold more dye. This extra dye means they give off more light than Y-chromosome sperm as the sperm pass through the laser beam of a high-speed sperm sorter in Johnson’s laboratory.
The sperm are collected in separate tubes with 90 to 100 percent accuracy and with much higher efficiency than in the original technology.
In a recent experiment showing the effectiveness of the sperm-sexing technology, eight litters of pigs were born at Beltsville, Maryland, using sorted X-chromosome sperm. Ninety-eight percent of the pigs, or 43 out of 44, in the eight litters were female.
Three control litters produced at the same time with unsexed sperm resulted in equal numbers of male and female offspring.
Johnson is collaborating with several scientists around the world to establish and perfect the technology for commercial development in livestock. To date, more than 500 animals have been born using sexed semen. All of the animals were healthy and normal. The sperm sorting technology has also been licensed for biomedical use in humans.
An in-depth article appears in the May issue of Agricultural Research magazine. The story is also on the internet at: www. ars.usda.gov/is/AR/archive/may99/accu0599.htm.
