|By Sarah B. Aubrey
PLAINFIELD, Ohio — Adding to 40 years of artificial insemination technology, now available commercially is gender-selected or sexed semen in beef cattle.
In 1989, Dr. Lawrence A. Johnson, head of the Germplasm and Gamete Physiology Lab in Beltsville, Md., first patented the methodology to separate X-chromosome (female) and Y-chromosome (male) sperm in cattle. The patented technology has been licensed by organizations, and after several years of field trials and initial release in the dairy industry, it is becoming an increasing factor in the beef cattle business.
Several organizations are offering this technology, but the basic science behind it is similar. According to USDA’s May 1999 Agricultural Research, determining the sex of semen is done by using a fluorescent dye that adheres to DNA of a semen sample.
This dye binds to the semen based upon how much DNA is in the sample. X-chromosomes in the sperm contain about 3 percent more DNA.
A machine called a flow cytometer sorts the dyed DNA using a laser beam. The sample gives off light relevant to its amount of DNA.
The X-chromosome contains more DNA, thus it glows brighter under the laser allowing the X and Y chromosomes to be separated and the semen to be sexed for likelihood of being male or female producing.
Sexing Technolo-gies and Genetics Resources International (GRI) have offered sexed semen since 1999. According to Gustavo Toro, beef breeds director at the Navasota, Texas location, 66 percent of their business is already in the gender selection market.
“We’ve had over half a million pregnancies with our system and we’re over 93 percent accurate,” he said.
Sexing Tech-nologies works primarily with large ranches that use the sexed semen with their elite cows, and they also export to countries like Australia, China and Latin America.
“It’s a huge impact on a herd to be able to tell the gender of the progeny and market for that,” Toro said, adding that he believes within the year a vast majority of beef breeders will begin to use this technology due to the benefit of being able to select for males or females, depending on individual needs.
Roy Wallace, of Select Sires, Plainfield, Ohio and a 40-year veteran of the AI industry, is not so convinced. He said that, while the sexed semen option is becoming popular in the dairy business, things like increased costs and lower conception rates will be too prohibitive for most beef producers.
“At this time we haven’t decided if we’ll do beef bulls with sexed semen, or not,” he said noting that Select Sires is already selling sexed semen on dairy bulls and this spring they are adding flow cytometry machines at their location. “Currently, only 1.2 million units of semen are used in the beef industry anyway and we only breed 3 percent of cows AI in America.”
Since the availability of beef sexed semen is limited until later this year, the cost is difficult to predict. Most companies agree that it will be significantly more expensive than conventional semen, though interviews with four different company representatives all declined to give a price range.
Monsanto has also joined the sexed semen foray and has licensed a technology called Decisive™ that will sex for females only. Genex-CRI in Shawano, Wis. is currently the only licensed distributor.
“One of the basic features is 85 percent predictability,” said Brian Naber, a brand manager for Monsanto. “It’s important for producers to realize that the 85 percent accuracy rate is an average-it takes large distribution (to attain that percentage).”
Naber said a producer would need more than 200 pregnancies to see the average of 85 percent females born, but that figure could still range for 80-90 percent heifers.
Another factor affecting distribution of sexed semen is availability on key bulls and high production costs. Wallace said that in using the laser technology, a significant portion of the fresh semen is destroyed when sorted, thus the collection and freezing rate of the sexed product is lower than conventional semen.