Primed sperm capsules point to easier breeding

Most Swiss cows are artificially inseminated Keystone

Swiss researchers have developed a way of boosting farmers’ chances of fertilising their cows with a sperm capsule that responds to ovulation cycles.

The research could even be geared towards humans in the future, according to the team at the Swiss Federal Institute of Technology in Zurich (ETHZ).

Most Swiss cows are artificially inseminated. While it is possible to tell from a cow’s behaviour when she’s on heat, it is not always easy to anticipate the exact moment of ovulation simply by observation. 

At the initiative of swissgenetics, one of the country’s biggest suppliers of bull sperm, bioengineers at ETHZ have developed a cellulose capsule that contains bull sperm and living cells that react to a particular bodily signal.

Hundreds of the capsules are implanted in the cow’s uterus a few days before ovulation. Cells in the capsules respond to the luteinizing hormone released during ovulation, releasing the sperm towards the fertilisable ovum. (See How it works)

The researchers say farmers will only need to know their cows’ estrous cycle and pinpoint the day ovulation is likely to occur. The capsules give the farmer a three-day period for insemination.

“The benefit is that we can widen the window of insemination,” Ulrich Witschi, deputy-director of swissgenetics, told swissinfo.ch

The bovine ovum has a lifetime of 24 hours and bull’s semen is good for around 20 hours. “We have to synchronise both events quite well. When we have this technology we can develop it into a product. Sperm will be released at the very moment [of ovulation],” said Witschi.

The biggest impact is expected to be on herders. Fertilisation is a very time intensive period for herders, requiring them to keep a close watch on cows to see when they ovulate. Theoretically, such a capsule would save the farmer time.

“Promising”

The Swiss Farmers Association welcomed the findings but wondered how expensive an eventual product might be, when compared with other artificial insemination capsules. Spokesman Thomas Jäggi said the research was “promising” although it was still in the laboratory stage.

“Once this new development is put into practice, it will improve farmers’ chances of breeding,” he told swissinfo.ch.

“It is often not easy to assess the best time to artificially inseminate a cow. With these capsules, which are released at just the right time, the chances of a cow being successfully fertilised are greater.”

An earlier and safer pregnancy will also help farmers save money, for example, if fewer inseminations are needed, or vet fees if there is no need for tests and infertility treatment.

“As such we welcome the research and new developments in this field,” said Jäggi.

More testing ahead

The research is only at the “proof of principle” stage, whereby tests among 16 cows showed embryo successes. The next stage will involve a short in-vitro phase to look at different components, followed by herd tests and large field trials.

The product also uses genetically modified cells, a component which swissgenetics says will require them to tread carefully, so as not to interfere with Swiss agricultural policy that frowns upon it.

Hopeful of success nevertheless, ETHZ has applied for a patent for the sperm release mechanism.

Helping humans too?

ETHZ will be in charge of any research under the patent into its possible use in humans, while swissgenetics will hold a licence for developing a product for use in animals.

The sperm capsule is currently geared towards the hormone balance and organism of a cow. The researchers say they would have to change several components of the genetic network and the kind of cells to adapt it other mammals, such as horses, and humans.

Species-specific cells and hormone receptors could be used to respond to differences in the structure of the luteinizing hormone of different animal species, ETHZ says.

Martin Fussenegger, in charge of the research team, is hoping to find an industrial partner to begin work on developing fertilisation capsules for human reproductive medicine. The university cannot produce the sensor cells on its own to required standards.

The idea is “revolutionary” for humans, he believes.

Christian De Geyter of the division of Gynaecological Endocrinology and Reproductive Medicine at University Hospital Basel told swissinfo.ch he was interested in the research and planned to contact ETHZ to find out more.

He said timing of ovulation was less of an issue in humans, as it was easier to predict and could be guided with medication. But sperm capsules could be used to freeze small amounts of sperm, he said. 

“Small numbers of spermatozoa cannot at present be effectively stored frozen, because of the risk of losing them. If we can put them into small semi-permeable capsules, it will be easier to trace them back after thawing.”

How it works

The cellulose capsule developed by ETHZ contains bull sperm and living cells. They are equipped with an additional genetic network that reacts to a particular bodily signal.

Several hundred of these tiny capsules are implanted in the cow’s uterus a few days before ovulation, where they remain until the animal is ready to conceive.

The hormone luteinizing, produced around ovulation, activates the genetic network. The hormone’s level in the blood shoots up within just a few hours and drops back down again after ovulation.

Sensors that are sensitive to the hormone sit on the cells in the sperm capsules and trigger reactions as soon as the hormone latches on.

The cells then form cellulase, an enzyme that dissolves the cellulose capsules from the inside until they collapse. The sperm cells are then released and swim toward the ovum.

The capsules are very small and so the cow would not feel anything. They can be implanted by the same plastic needle they have used to insert bull sperm in the past. 

(Source: ETHZ)