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All The Sex You Want

A simpler way of predetermining calf sex appears to be on the horizon.

Choosing your calves' sex may soon be as easy as picking a colored straw of semen. Want a heifer, select a pink straw; a bull, take a blue. A new technology to be marketed by Toronto, Canada-based Microbix Biosystems is said to be a fast, inexpensive, non-invasive technique to separate male and female sperm.

In mammals, the male sperm determines the sex of an offspring. Females produce egg cells with only X chromosomes, while males produce sperm cells with either an X or Y. If the fertilized egg is a double XX — an X from the male and an X from the female — it will produce a female. If it is an XY, a Y-bearing sperm fertilizing an X egg, it will produce a male offspring. Microbix's process works by separating the X from the Y sperm.

“The process will be marketed as two kits (male and female). Each kit will contain the sex-selecting chemicals, packaged in a powder formula and a sterile saline solution for mixing. Just add the appropriate sexing solution to the ejaculate and twirl gently for 15 minutes,” explains Microbix spokesman Peter Belcher. “The sperm of the undesired sex clumps together and gets trapped when you pour it through a very basic filter.”

Belcher says laboratory and field-testing indicate the sperm remain completely unharmed. In fact, he adds, you end up with a much higher-quality sperm.

“One of the fortuitous side-effects is the filter process not only traps the sperm of the undesired sex, but also fractionated, broken and immotile sperm of low quality,” he says.

Targeted selection

Livestock producers pay billions of dollars annually on artificial insemination (AI) without certainty they'll end up with animals suitable to their needs. Producers want their best animals to produce heifers to improve herd genetics; they want the rest to produce bull calves to take advantage of the male's improved gain efficiency. The laws of probability, however, dictate 50% of all offspring will be the wrong sex.

“Every animal producer operates on 50% efficiency,”Belcher says. “When you multiply this — given the multibillion dollar size of this global business — it's mind boggling.”

Technically producers would be able to build a herd twice as fast than with conventional breeding methods.

“From a producer's standpoint, you'd get a lot of cost savings. Being able to maintain the heifers' bloodline and have bull calves out of the rest, that would be the perfect world,” says Tim Nerbas. He runs a 100-head, cow-calf operation near Waseka, Saskatchewan. “If it's priced reasonably, about the only downside of sex-selection technology I can think of is it might reduce the genetic diversity in the North American herd.”

Belcher says males convert feed to lean-muscle mass 15% more efficiently than females.

“Anything in agriculture that improves efficiency by 2-3% is considered significant. If, all of a sudden, you can create a landscape where all your feeder animals are male and converting feed, which is your largest variable cost, into lean-muscle mass at 15% or 16% greater efficiency, that's very significant. It's win-win on a lot of different angles,” Belcher says.

Early 2008 rollout

Belcher claims Microbix's sperm-sexing technology is simpler and less invasive than the flourescent-activated cell (FACS) technology currently used. With FACS, the sperm nucleus is stained and X and Y sperm are identified one at a time as they pass through a small aperture.

Since the nuclear material in an X chromosome is physically larger than that in a Y, the X chromosome picks up more stain and glows more. Staining the nuclear material of the sperm you'll use for fertilization is invasive and costly, he says.

“Our technology doesn't involve any genetic altering; there's no staining or flourescents or other manipulation of the sperm,” Belcher says. “The sperm is left completely unencumbered. It's simply collected and frozen, exactly the way it's been done for AI the last 40 years. The only thing we're doing is separating off the sex we don't want.”

Microbix expects to complete development and field trials over the next 1Ω-year period, and have the technology on the market by early 2008. Prices are yet undetermined but Belcher expects it to only nominally increase AI cost.

Lorne McClinton is a freelance agriculture writer based in Yellow Grass, Saskatchewan, Canada. Suzanne Deutsch is a freelance writer based in Greenfield Park, Quebec.

Not just cattle

Since sperm sex markers are very similar in all mammals, Microbix Biosystems' sperm-sexing technology will work for all, with minor variations.

“There are only very minor differences between the markers in cattle, hogs, horses and dogs, or any other mammal you can think of,” Microbix Biosystems spokesman Peter Belcher says.“Once we've developed and commercialized the kit for one species, we believe it will be very straightforward to do all others.”

TAGS: Breeding