Sexed semen: Get what you want


SALEM, Ohio – Dairymen want replacement heifers. Beef feedlot operators like fast-growing steers, and market hog producers favor lean gilts.

Producers keep their fingers crossed at breeding time: The chances of getting young animals of the desired sex, regardless of the outcome of the dam’s prior matings, have the same odds as flipping a coin. It’s all up to the sire and luck of the draw.

Until now, that is.

Research and technology originating in the United States is clearing a path that will allow producers to predetermine the sex of their dams’ progeny, a move that is giving artificial insemination an entirely new meaning.

Sex-selection. Colorado-based XY, Inc., is emerging as the world leader in the research, development and commercialization of sex-selection techniques in non-human mammals, including cattle, horses, sheep and pigs.

Formed in 1996, the company’s initial mission was to offer gender selection to the United States dairy industry by way of sorting sperm as an enhancement to artificial insemination. The company is now licensed to pursue sperm sorting in non-human mammals using technologies developed by USDA, Colorado State University and Cytomation, a company that develops advanced flow cytometers used in the sorting procedure.

Work in Beltsville. The concept of the now-patented Beltsville Sperm Sexing Technology was developed in the early 1980s by animal physiologist Lawrence A. Johnson and colleagues at the USDA Agricultural Research Service Germplasm and Gamete Physiology Laboratory.

Improvements to the method resulted in births of the first animals in 1989, according to H. David Guthrie, a research physiologist at the Beltsville facility. Today, research continues on preservation of sorted sperm at the Maryland lab.

“The emphasis now is on cryo and low-temperature preservation to enhance efficiency,” Guthrie said. “There is still room for improvement in coloring the sperm and storage methods.”

Sorting method. The method separates living female-producing X-chromosome sperm from male-producing Y-chromosome sperm based on their content of DNA.

The technology uses a fluorescent dye that sticks to sperm based on how much genetic material the sperm contains. The X-chromosome sperm contain about 4 percent more DNA and therefore hold more dye, giving off more light than Y-chromosome sperm as they pass through a laser beam of a high-speed sorter in the laboratory.

The sperm is collected in separate tubes with 90 to 100 percent accuracy, Guthrie said.

The method has applications in nearly all mammalian species, including domestic farm animals and endangered and zoo animals, Guthrie said.

The day is coming where producers will choose not only the sire for artificial insemination, but also whether they would like male or female progeny.

Success. Since the technology’s refinement, the successes have been many: XY scientists produced “Call Me Madam,” the world’s first sex-selected foal, in 1998; live births of multiple litters of piglets using gender-selected semen; and the first sex-selected foals and a calf using frozen sexed semen and artificial insemination were born in 1999.

In October 2001, XY researchers watched as the first sex-selected lambs in the world were born from use of low doses of sperm that were sorted, frozen, thawed and artificially inseminated into the ewes.

“The birth of the lambs in Australia proves the sperm-sorting technique, combined with freezing, thawing and artificial insemination, is now sufficiently robust in sheep to work outside the research lab,” said Mervyn Jacobson, chief executive officer of XY.

Prior to recent breakthroughs, researchers were concerned with the viability of the sperm once it was sorted, frozen, transported over long distances and thawed – the popular handling method of sperm used in conventional AI practices.

Today, artificial insemination is used in approximately 65 percent of dairy breeding as well as a beef and horse production.

In 2000, XY licensed a company to offer sorted semen for dairy cattle commercially in the United Kingdom. Sorted semen should become commercially available in the United States within the next few years, according to the XY Web site.

Benefits to breeders. Determining offspring sex before they’re born has clear-cut advantages for breeders.

“This can be used to make agriculture more efficient. We don’t need males for dairies, and in most situations on swine operations, females are leaner and more desirable,” Guthrie said.

The technique could also be used to reduce dystocia in heifers by breeding them to have smaller heifer calves and breeding only older cows to produce bulls.

In dairy operations, use of sorted semen could allow producers to mate only the best cows in the herd with top bulls to produce replacement heifers. The remainder of the herd could be mated with top beef-breed bulls for market beef or veal production.

Since the technique’s need for precision and high accuracy, sorting is a slow process. Though lasers need only microseconds to sort the sperm, a maximum of 70 million sperm of each sex can be sorted in one day in the laboratory, Guthrie said.

The process currently lacks speed to make the semen widely available; though beef cattle need “a few hundred thousand” sperm for traditional AI and 10 million for cervical insemination, swine require between two and three billion sperm for successful fertilization, according to Guthrie. When the numbers are added up, an entire day’s work still falls short of separating enough hog sperm for even one attempt at insemination.

Current research offers hope, however. It usually takes 60 million sperm to impregnate a ewe using standard artificial-insemination techniques, but researchers accomplished the October sheep pregnancies using only four million sperm.

Domestic proof. Accelerated Genetics, based in Westby, Wis., partnered with XY to conduct the first organized sexed semen trial by an artificial insemination company in the United States last year and is continuing to collect and verify real data, according to CEO Roger Ripley.

“The technology is fairly slow and expensive, and we’re trying to find out of it’s practical from a commercial standpoint,” he said.

The sexed sperm would be available at a premium cost, he said.

“There’s always been a big interest in controlling the sex of farm animals, particularly because of the shortage and price of replacements as far as expansion goes,” he said.

The technology also offers a biosecurity buffer by allowing farmers to create their own replacements instead of bringing in heifers from another farm or location, Ripley said. England and European countries have specific interest in using sexed semen for replacements as a way to rebuild and replenish herds after foot and mouth disease outbreaks, he said.

“Looking at the new technology, there’s no magic answer to any of it. There’s a definite learning and development curve and right now things are a bit on the costly side,” he said.

“That doesn’t mean that down the road in a short time things won’t be faster and more economically priced. It’s still early and producers need to be patient,” he said.

For exotic or endangered animals, the technology can be used to replenish populations and expand breeding stock, Guthrie said. The sperm sorting technology has also been licensed for biomedical use in humans.

(You can contact Andrea Myers at 1-800-837-3419, ext. 22, or by e-mail at

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