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How Stem Cell Technology will Improve Cattle Breeding

Author: Kristy

Updated: 10/07/2015

Berry College may seem an unlikely place for the next big thing in cattle breeding, but that’s because you don’t know Kyle Caires.

The bright young animal science professor is advancing his cattle stem cell transplant research at the private school 70 miles northwest of Atlanta near Rome, Georgia. While it isn’t exactly known for agriculture, the sprawling 27,000-acre campus allows plenty of room for an Angus cattle herd and offers students a rich curriculum in animal science.

It also offers Caires, a Hawaii native with animal science and reproductive biology degrees from Oregon State and Washington State, a place to do his cutting-edge stem cell work. He came to Berry College five years ago with the specific idea of perfecting the next generation of cattle-breeding technology.

His subject is adult stem cells. They are not to be confused with embryonic stem cells, which develop into the building blocks for embryos before birth. Adult stem cells continue to work throughout life in animals to replenish dying cells and to repair damaged tissues such as muscle, skin, and other organs to maintain normal function.

Sustained fertility
The adult stem cells Caires is after are called spermatogonial cells. They are in a bull’s testicles and are the foundation for sustained fertility through self-renewal and differentiation – making sperm. These cells are the only adult stem cells capable of transmitting a bull’s genes to his offspring. Caires’ technique finds them and then makes them work more broadly and efficiently.

“It’s always bothered me that once a bull is gone, he’s gone. There’s no way to preserve him,” says Caires. “You can freeze his semen, but even that is exhaustible. This technique we are developing can solve this issue.”

It harvests the stem cells from a donor bull and transplants them into a recipient bull or bulls. When successful, the recipient bull produces sperm carrying only the genetics of the donor. Caires’ earliest work removed the testicles of the donor bull. Now he has perfected a minimally invasive surgical technique for both harvesting and implanting stem cells into the recipients. He compares it with taking a biopsy of the testicles from the donor, and then using a similar surgery to implant it into the recipient’s testicles. It’s a tissue transplant.

If that sounds simple, think again. First off, Caires has to know where to find the correct adult stem cells. Then, of all the cells extracted in the biopsy, he has to identify, under microscope and through tissue culture, the exact stem cells that produce sperm.

“It’s the hardest part,” he says. “It’s like trying to find a needle in 25 haystacks. We have found some marker genes that help us identify them.”

The correct stem cells have to be multiplied in a lab culture dish before they are transplanted into the recipient bull. They have to be put in just the right place where they will engraft and colonize the recipient bull to produce sperm that is the same as the donor bull.

Caires’ initial research for harvesting and culturing the stem cells was with mice and pigs.

“Believe me, I hit my head against the wall many times, but we have developed this technique to harvest, culture, and transplant the stem cells so they will establish themselves and eventually produce sperm,” he says.

The recipient bull is first sterilized so that when the transplant stem cells take over, only sperm that matches the donor bull is produced. Calves sired by natural mating or artificial insemination (AI) will carry only the donor’s genes and are his offspring genetically.

The best news in this technique, says Caires, is that you can increase the capacity of semen produced from the donor; it’s no longer an exhaustible supply. That could lower the cost of elite bull semen to cattle producers. Like AI and embryo transfer in earlier generations, the stem cell technique multiplies the breeding power of an elite animal.

Caires points out one example of how the stem cell technique could be put to good use. A pair of hot AI bulls in the Angus breed include Tour of Duty (semen available from AI firms ABS and ORIgen) and Ten X (Accelerated Genetics). Unfortunately, the demand for their semen far outweighs the supply. Sometimes, good bulls like them are relatively poor producers of sperm from a volume standpoint, and they may be hindered by age or injury.

“Several bulls in the dairy industry have had back orders of five to seven months. When you get it, it’s expensive and out of the range of many producers,” explains Caires.

“With our technique, we could essentially put one of those bull’s stem cells in another factory – recipient bull or bulls – and increase the supply of his semen and lower the cost of production for everyone involved,” he says.

A competitive industry
The exact techniques Caires uses for his genetic transfer procedure did not come easy, and he’s cautious in sharing them. Stem cell research is a very competitive field now, and there’s widespread interest from AI studs, breed associations, and ranchers. Other researchers are working on similar projects, and a race is on to bring it to fruition.

Caires says his techniques and process are not very expensive. He estimates that the cost to harvest stem cells, identify the correct ones, grow them, and implant them is about $3,000 per procedure.

“I don’t have a lot of fancy equipment. I do most of this work – from the biopsy and surgery to lab work – freehand. I’ve done it enough that I’ve gotten pretty good at it. I’ve used ultrasound equipment to help transplant and deliver the donor stem cells into the correct location, but it’s become second nature so I don’t really need ultrasound,” he says.

While Berry College may not be a household name in the cattle business, Caires says his work aligns well with the college’s motto: Experience it firsthand.

He involves undergraduate students in all aspects of his innovative research.

Caires is also careful to remind that this is still a work in progress, and it could be a couple of years before he publishes his official research results. It may be a few years after that until the practice is widely in use.

He’s guarded about his exact success rate, but says it is over 50% (recipient bulls producing the donor sperm) and improving all the time. Part of the problem is getting the recipient animal to accept the transplanted stem cell tissue, just like any other organ transplant.

“Cattle aren’t the easiest animals to work with on this,” says Caires. “Research mice are fairly highly inbred, so animal-to-animal transplant acceptance and success is a little easier. In cattle, that’s not true. We’re getting better, though, and this will be accepted technology in the future.”

Improving cattle breeding
Justin Green of Arrow Brand Genetics, an Angus breeder in Maddock, North Dakota, sees stem cell work such as Kyle Caires is perfecting as a logical new advancement in cattle breeding, following artificial insemination (AI) and embryo transfer (ET). Green thinks it may enable seed stock producers such as Arrow Brand to skip an entire generation in getting the best genetics to commercial cattle producers.

Right now, he says, breeders identify an elite bull and use AI to produce sons from him for sale to commercial producers. With stem cell technology, the elite bull’s genetics could be transferred into recipient bulls and put to use almost immediately, rather than waiting for his sons to grow up and prove themselves. “It would let us skip one whole breeding cycle. It would take cattle genetic advancement to a whole new level,” Green says.

Like AI and ET, Green thinks stem cell transfers will gradually become commonplace. “I don’t know if it will be in five years or 20 years, but it will be the new way that we get the best genetics out to farmers and ranchers,” he says.

It can take eight or more years to find out if a bull’s daughters are functional brood cows. By that time, he is usually long gone. Using Caires’ technique of freezing stem cells may be one way to propagate the bull’s genetics long after his own productive life.

Caires sees several other ways that stem cell technology might be put to use by commercial cattle producers. One is to use it in cleanup bulls. If you AI your cowherd, some of them always return to heat, necessitating less expensive cleanup bulls to catch them on pasture. Those cleanup bulls could be recipients of stem cells of the AI bull or your herd sire, thus, siring calves with the donor’s genetics. This would give an increased uniformity of the calves – 100% of them from one bull.

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