CHUTESIDE MANNER: Exploring the Frontier of Animal Health, Surrogate Sires
By Patti Wilson, Contributing Editor
Chances are pretty good that if you’ve owned beef cows, you are familiar with artificial insemination (AI). You’ve either employed the process in your own herd or purchased breeding stock that’s the product of a technique this country has practiced for 75 years. It has vastly improved our livestock genetic base in every species. Technology Pushes ForwardWe have seen advancements in AI, including improvements in semen handling (remember glass ampules and ice water?), better insemination guns and more protection against contamination, all of which have improved conception rates. More than 8.7 million units of beef semen sold in the United States last year – a testament to the success of this process.
Timed AI and heat synchronization have also evolved over the past 50 years; embryo transfer and cloning followed more recently.
The latest development in reproductive technology is one to blow your imagination into the next county. A group of scientists is developing “surrogate sires.” According to Chad Dechow in a February 2022 Hoard’s Dairyman article, “A surrogate sire produces sperm like any other male, but with one key difference: The sperm they produce is not their own. They produce sperm using cells from a genetically superior donor male.”Simply, a surrogate candidate must have functional testes that can produce sperm. He must also be incapable of producing his own sperm. Sounds bizarre, right? Dechow goes on to say that decoupling that connection was elusive, but it has recently been accomplished. Mice, goats and swine have successfully surrogated; development in cattle is well underway.
Who Is Doing This?
Jon Oatley, a reproductive biologist with Washington State University (WSU) leads a team that includes researchers at WSU, Utah State University, University of Maryland and the Roslin Institute at the University of Edinburgh in the United Kingdom.
How Do They Do It?
A Project Topics article published by Ajisebutu Doyinsola this year reported that Oatley and his team used the gene-editing tool, CRISPR-Cas9, to “knock out a gene-specific to male fertility in the animal embryos that would be raised to become surrogate sires. These male animals were all born healthy. They later received transplanted sperm-producing stem cells derived from donors.”Later yet came confirmation of active donor sperm being produced by the experimental male subjects. The process to this point (transplant to sperm production) takes three to five months. Tests done in mice have yielded healthy offspring carrying the donor’s genetics.
Who Needs It?
Beneficiaries of the technique would first include goat or swine breeders in remote or underdeveloped areas who don’t have access to AI technology; goats (an important source of global protein) must be inseminated laparoscopically requiring a surgical procedure. A reproductive specialist and sterile facilities are needed. Swine semen is almost always used fresh for better conception results. This makes access to superior boars and prompt transport of semen strategic to success.
Dechow also mentioned an additional possibility: “Stem cells from a newborn bull calf could be transplanted to a mature surrogate sire to facilitate sperm production well before that bull calf becomes sexually mature. Stem cells could, in theory, be harvested from a developing fetus even before a calf is born. Because fetal germline stem cells are present early in fetal development, it is conceivable that semen from a bull calf will be produced even before that calf is born!”Public PerceptionNatalie Grover, science correspondent for The Guardian, wrote in September 2020, ”Sometimes … it’s not appreciated that we have been engineering animals for probably 10,000 years, ever since domestication of livestock. They were combining genetic material through forced reproduction and therefore engineering a genome that may not have developed just through animal natural selection … We’re just doing it in a more precise and efficient manner.”Regardless of any success on a scientific and practical level, real-world, widespread use of surrogate sires will ultimately come down to public acceptance. Government regulatory consideration will no doubt come into play because surrogates are made through a gene-editing process. This may prevent them from entering the food chain. However, the donor genetic material (sperm) is not genetically altered. Only time will tell on the outcome of an upcoming (and unnecessary) moral conundrum.
Allison Van Eenennaam, Ph.D., a University of California scientist, said in The Guardian article, “ The technology is unlikely to be commercialized if regulated as a genetically modified organism (GMO).” Consequently, researchers have a long struggle in proving this technique acceptable in public perception. She stressed, “Perception plays a role in shaping regulation, which is subject to being swayed by activist groups that have historically mounted intense opposition.
All that does is slow down the rate of genetic improvement, which has a negative impact on the overall sustainability of agriculture.”Researchers have pointed out that the technology could easily be put into production in sparsely regulated South American countries like Argentina and Brazil.
Technology is almost always beneficial; however, for fun, let’s look at this matter subjectively through the eyes of a U.S. rancher. Many thousands of high-quality bulls are developed and sold in this country each year, their producers using all means available to maximize genetic progress. They provide service to a majority of our national cow herd, doing their job while eliminating the time-consuming task of AI. Beef herds that AI also depend on these bulls as cleanup sires after insemination season is completed.
A question remains about where a surrogate sire would fit in our system.
Other than the obvious genetic advancements, why do we AI in the United States?
- Bulls can be mean. Dairy bulls, in particular, are lethal.
- Bulls often get hurt. Semen tanks never suffer from injury, pinkeye or hoof rot.
- Good bulls are expensive. Most semen is cheap. I don’t know what one of these surrogate bulls will cost, far out in the future, but I’m guessing it would be a great amount The prohibitive cost would likely not be worth the risk of keeping a live bull around.
- A sire may last from two to 10 years, depending on luck. Semen can be stored indefinitely.
This is not to say that surrogate sires would be a great asset in an underdeveloped country where access to most modern necessities, such as good roads or sterile surgical areas, just don’t exist.
It seems we have plenty of time to consider our opinions on this latest reproductive advancement. Perhaps several years from now we will see some of these bulls trickle into the U.S. beef system.
What interesting thoughts to ponder, and what incredible things technology is doing for us, with potential that seems unlimited.