Don’t put all your eggs in one petri dish: IVF a viable option for quick genetic turnover
In dairy cattle, bull calves are generally an undesired outcome, but with innovations progressing in in vitro fertilization, males can become nearly obsolete, and, in both dairy and beef cattle, sought-after genetics can become more readily available. Several IVF companies, including Trans Ova and VyTelle, have been expanding with satellite sites across the nation for lab work and oocyte collection.
IVF generally wins over embryo transfer in terms of prepping cattle. Typically, IVF requires one shot to embryo transfer’s eight to 10 shots prior to embryo retrieval. With Vytelle’s new technology, follicle stimulating hormones (FSH) are unnecessary.
“We are able to utilize non-stimulation and able to grow those into healthier embryos in the lab,” said Taylor Grussing, special projects manager with VyTelle. “We like to say it’s low stress on cow as well as cattleman.”
Even with practices that still require a shot, oocyte can be collected at any point in the cycle, from 15 days postpartum to 100 days pregnant, with two weeks in between collection, Grussing said. Most use IVF to increase genetic turnover, but it can also be a tool best applied to unique circumstances.
Dave Winninger, an AI technician near Cody, Wyoming, has been working on a project with farmers in Massachusetts who wish to get offspring for very rare and old semen to enhance traits in their dairy cattle that they feel has been lost throughout the years.
The bull calves yielded from the semen collected in the 1960s, ’70s, and ’80s would be unwarranted, Winninger said. The heifers, on the other hand, were highly desired, so with reverse sorting of the semen, of the 120 IVF embryos, all but one of the 50 calves yielded was heifers.
“They got to avoid having all the male calves, which would have been a waste in this project,” Winninger said. “They got away with only one male calf. That’s the power of that technology.”
IVF can be greater in cost than conventional ET, but more viable embryos can offset the initial expenses. Vytelle’s technology that eliminates the need for FSH minimizes the cost as well.
“It’s more economical and on a per embryo basis,” Grussing said. “If you only get five embryos, you only have the cost of five. Before, there was a lot of expense setting up the cow.”
This technology also leads to healthier embryos with less large-calf syndrome happening.
IVF is also highly useful for cows that cannot get pregnant due to age or other circumstances or that underperform with embryo transfer practices. Such was the case of a particular cow of Dale and Nancy Venhuizen’s, of Churchill Cattle Company in Manhattan, Montana.
“We had a couple of donors that were really good but wouldn’t fertilize any embryos when we did ET,” Dale said. “We changed one donor in particular to IVF in 2014, and she worked fantastic. We got six or eight calves out of the very first flush, when before, we had been getting nothing.”
Dale spoke to varying experienced people in the industry with no reason for such a situation, but he gladly continued IVF with that donor to great success.
In the summer of 2018, Trans Ova reached out to the Venhuizens regarding a satellite center in Montana, where they aspirate outside clients’ cows every other Wednesday.
A typical aspiration generally yields about 20 oocytes from each egg, which are then transferred to labs by the next morning. The oocyte is fertilized and, if viable embryos are produced, will be implanted into a recipient cow on day eight of the cycle. An estimated 30 percent of oocytes will turn into embryos, Dale said.
The pregnancy rates in IVF are about 10 to 15 percent lower than conventional embryos, but the opportunity for more calves from one animal is an obvious advantage.
“One of the big advantages of IVF is that you can use several different sires and really spread out your risk,” Dale said. “We’re always trying to do that, and it allows you to do a little bit of an experiment.”
IVF also allows a cow to stay within a regular calving cycle, if desired. Calving her versus keeping her open allows her to stay healthier and not become overweight, making her hard to breed and hard to donate.
“If you want to flush a donor but want her to calve in February, you can flush her in late March, two times in April, then breed her in early May. Then you can wait maybe 40 days and do her while she’s pregnant,” Dale said. “That’s a wonderful tool because if you do conventional ET, you get one flush then breed the cow back.”
Recipient cows can absorb or abort IVF embryos a bit later than recip cows generally will with ET embryos.
“The recip cow has way more to do with what your preg rate is than if your embryo is conventional or IVF,” Dale said. “The industry rate is around 50 percent, and if we can bump that number up 10 percent by fine tuning some processes as we get more knowledge of the ideal implant times of recip cows and other protocols, IVF would be a simply amazing tool.”