‘Super Daddy’ Animals With Elite Sperm Could Breed Their Way to Climate Change Survival
Livestock with gene-edited testicles can help humans survive an increasingly food-insecure world
In a Pullman, Washington, laboratory barn, goat #1962 has one purpose: Go forth and multiply.
#1962 is in the world’s first-ever generation of a gene-edited “Super Daddy” or “Surrogate Sire” goat. This means he has the balls (literally) to pass on not his but another, more elite buck’s DNA.
Project leader and reproductive biologist Jon Oatley, PhD, has been working on the concept for 20 years. He believes surrogate sires will be key to breeding livestock that produce more meat, dairy, and fiber while withstanding the effects of climate change.
“As the climate changes and populations grow, we’re asking animals to do more for less,” Oatley tells Future Human. “If you can change the genetics, that is an intrinsic variable in an animal that can influence how easily they convert inputs to outputs.”
Breeding surrogate sires, as Oatley and his team describe in a new study published in the Proceedings of the National Academy of Science, is a two-part process. First, the gene-editing tool CRISPR is used to create sterile male goats, pigs, and cattle. Then, stem cells from another male animal of the same species are implanted into their testicles, resulting in a male that can pass on the genetics of a different male. The six-year study is a collaborative project between researchers at WSU, Utah State University, the University of Maryland, and the Roslin Institute at the University of Edinburgh.
The surrogate sires project is a rapid-response strategy to quickly and efficiently breed climate-resistant livestock, Oatley says. Take, for example, the Nelore cattle breed.
A large, tough breed that sports loose, thick black skin and white hair that reflects the sun’s rays, the Nelore is the most popular cattle breed in Brazil because of its resistance to heat and insects and its ability to withstand extreme weather. The Nelore doesn’t produce as much meat as the most popular beef cow in the United States: the Aberdeen Angus, a much shorter, heavily muscled black cow. But if you send an Angus to South America, it won’t survive long in the hot, harsh conditions it’s not adapted for.
But imagine a gene-edited Nelore bull with the semen of an Angus. If you put him into a herd of Nelore females, says Oatley, he could easily father many crossbred offspring without suffering in the Brazilian climate, the way a regular Angus bull would. From that first generation, ranchers could select the most meat-productive, climate-adapted cows for future breeding, effectively creating a new cow that survives in South America but also produces a lot of meat.
That’s the magic of surrogate sires, Oatley says. Once they’re created, they can be used to make genetic improvements in the most simple, low-tech way possible. All these “super daddies” have to do is what they’re naturally inclined to do: breed.
The developing world’s problem with subpar genetics
Livestock in developing nations, says Steve Kemp, PhD, a professor at the University of Edinburgh, has been “selected to stay alive and they are pretty good at that, but not much else. They mostly stand around and produce greenhouse gas.” Kemp is currently based in Kenya, where he’s the program leader for livestock genetics at the International Livestock Research Institute (ILRI), a multinational research center working to improve food security and nutrition in developing nations through better livestock farming practices.
Animals are crucial for human survival in the face of climate change, especially in developing nations where vulnerable populations raise livestock on marginal lands that are unsuitable for growing crops. (According to the Food and Agriculture Organization of the United Nations, 60% of global agricultural lands aren’t suitable for crop production but can be used for livestock.) Animals are also more resilient to climate shocks than crops. They can be moved out of the way of extreme weather or brought to food and water. Crops can’t.
At least 1.3 billion people worldwide depend on livestock to make a living. Meanwhile, climate-related disasters led to a 36% loss in livestock productivity worldwide between 2006 and 2016. As this trend continues, says the FAO, it will lead to a “downward spiral of increased food insecurity and malnutrition.” That double whammy of a more extreme climate, plus the predicted addition of 2 billion more people to the planet over the next 30 years, means feeding and clothing the world’s most vulnerable populations will depend even more heavily on livestock production. Humans are expected to produce 376 million tons of meat per year by 2030 — a 72% increase from the 218 million tons we produced in 1999.
But more livestock means more gas. Currently, livestock is responsible for 14.5% of global greenhouse gas emissions.
The need for more meat to survive climate change will have the ironic downside of contributing to climate change — unless we can raise fewer animals but get more out of them. In other words, we don’t need more livestock; we need better livestock.
Developed nations have managed to do this already. In the U.S., livestock contributes only 4% of the total greenhouse gas emissions, in part because beef and dairy herd numbers have dropped significantly in size over the last 100 years while producing increasingly more meat and milk — largely due to years of selective breeding.
These techniques, however, simply don’t work in developing nations.
“The history of animal breeding in Africa is littered with the failures,” says Kemp. “People come and say, let’s sort you out, animal breeding 101, this is how you do it. Repeatedly they have failed to set up sustainable breeding schemes.”
A typical cow in the developing world produces one to four liters of milk a day, Kemp says. That’s just a 10th, maybe a 20th, of what an average dairy cow gives in developed nations. And it’s not just milk: Production of beef and eggs in developed countries has risen relentlessly, Kemp says. Not so in other parts of the world.
“If you look at any of those factors in East Africa, Kenya, Ethiopia, you see an absolutely straight line. In fact, you’d probably see a slightly declining line,” he says. “There’s absolutely no improvement.”
Lower productivity can’t be blamed entirely on poor genetics — housing, veterinary care, welfare, and feeding strategies play their part as well — but there is “no doubt genetics plays a large part,” Kemp says. Because of bad genetics, small farm holders — who, with just a few acres and a handful of animals, provide about 80% of the food produced in Asia and sub-Saharan Africa — end up trapped in a cycle of unproductive, unhealthy, and poorly fed animals. Breaking that cycle depends on several factors, but nothing can change without the right genetics.
“If you haven’t got the potential,” Kemp says, “it doesn’t matter how much you feed them.”
One of the biggest obstacles to improving their animals’ genetics is the supply chain: Specifically, getting the right sperm to the right female at the right time — before it thaws out.
Artificial insemination — the original “A.I.” — is a widely used method of collecting semen from males with elite genetics and then breeding them to females. A.I. has had a significant impact on increasing livestock performance, especially in the U.S. dairy industry.
To perform A.I., sperm is first collected from a donor male animal using an artificial vagina — a tube with an outer rubber lining filled with warm water that uses thermal and mechanical stimulation to induce ejaculation. In developed nations, especially in the cattle industry, there are farms that house elite bulls for the sole purpose of collecting, freezing, and shipping their semen to buyers around the world.
Once collected, semen is preserved in “semen straws” and held in liquid nitrogen tanks until a female in heat is ready to be impregnated. For most types of livestock, breeding needs to happen within a narrow, 12-hour window when the female is ovulating. Many U.S. dairy farmers are trained to do their own A.I. breeding and have a nitrous tank of preordered semen straws ready to use when they notice a cow in heat. Others employ a local A.I. technician to do the deed.
But developing nations like Africa aren’t equipped to support A.I., from start to finish, Kemp says. A farmer might miss a heat cycle if they aren’t carefully observing their animals morning and night, if they don’t keep good records of heat cycles, or if their animals aren’t cycling regularly due to stress or lack of nutrition. They may not be able to find the right precollected semen because centralized semen collection services making semen locally available don’t exist to the extent they do in the developed nations. Even when sperm is available at the right time, A.I. technicians, armed with Thermos flasks of cooled semen, navigate bad roads and extreme temperatures as they race toward farms while preserving their cold chain, Kemp says. More often than not, it doesn’t work, and A.I. breeding attempts fail, costing farmers money. Furthermore, A.I. has never been used extensively for small ruminants, but goats and sheep are more important to small farm holders in developing nations than cows, Kemp says. A.I. for small ruminants requires a more intrusive procedure and well-trained technicians, and it’s harder for farmers to detect their heat cycles than those of cows.
ILRI has well-established community-based breeding schemes with goats and sheep encouraging farmers to get together and share their best animals to improve their local herds, Kemp says. It’s been effective, but improvements are limited by the genetics of nearby animals. With a surrogate sire program, genetics could be introduced from animals anywhere around the world.
That’s why a goat like #1962 is so exciting.
“Putting elite semen into hundreds, potentially thousands of males and sending them out as a living, breathing Thermos flask” is a game-changer, Kemp says. “Not only do they maintain that semen in good condition, they detect exactly when that semen is needed, and they deliver it.”
American farmers aren’t struggling with such an extreme productivity crisis, but surrogate sires have huge potential to improve U.S. livestock too, says Oatley. Specifically, their ability to efficiently convert feed to meat, dairy, and fiber. And that could have a significant impact on U.S. agriculture overall.
“Less feed having to go in means less farming the feedstuff we need to put into livestock,” he says.
CRISPR for creating sterility
The surrogate sire concept has been a bit of a holy grail in livestock reproductive schemes.
Sexism aside, any animal breeder will tell you that the biggest impact and most immediate gains in herd quality comes from having elite male genetics. A really great male specimen can produce hundreds or even thousands of offspring in a year. Females may end up doing all the work, but they can only contribute their genetics to a fraction as many offspring.
But to create surrogate sires, you need to inject stem cells into the testicles of sterile males. If a male isn’t sterile, it’ll keep producing its own sperm rather than the desired elite sperm. The biggest barrier to the strategy was finding an easy way to make males sterile, said Oatley.
Scientists were able to decrease sperm production in mice after exposing mice testicles to radiotherapy or chemotherapy. But this didn’t scale up to livestock.
“There is a welfare concern. There is a biohazard concern,” Oatley says. “Think about putting a chemotherapeutic drug into a 2,000-pound bull? Forget it — it’s not feasible.”
So, they were stuck, Oatley says, until the revolutionary gene-editing tool CRISPR-Cas9 became widely available. As he and his team describe in the new study, they successfully removed the fertility gene, called NANOS2, in mammals for the first time ever. Doing so created so-called “knockout” males, which are completely normal except for the fact that they’re sterile.
Once they had sterile males — goat #1962 was one of five born in Oatley’s lab — the team injected donor sperm-producing stem cells into their testicles. As the young goat’s reproductive organs developed, the team collected semen and confirmed that yes, #1962 was producing live sperm. Just not his own.
The science is there, the regulations (and people) aren’t
Oatley foresees the biggest challenge to moving surrogate sires into farm-level production will occur at the regulatory and public perception level. But there is no time to be lost.
“We have to do this. If we want to have civilization persist as it is, and also have food security, we need to do these things,” Oatley says in a video explainer recorded by the Washington State University College of Veterinary Medicine. “We as a population have to decide this is something we’re going to do.”
There is some science to be finished. Oatley and his team need to increase the sperm production levels, which has already been accomplished in early experiments with mice. He expects another one to two years to complete that process in goats and pigs. Three in cattle. And then there are all the other animals surrogate sires could be used for, including endangered species. Though they have only made surrogate sires in mice, goats, pigs, and cattle, there is “no reason that it wouldn’t work in any mammalian species,” Oatley says.
He is much more concerned about the regulatory roadblocks and frustrated by the negative public perception of gene editing.
In the United States, the Food and Drug Administration has regulatory authority over gene-edited livestock. Gene-edited animals have to undergo extensive review before they can enter the food supply chain. There are currently no FDA-approved, gene-edited livestock products on the market. According to a 2018 study by Pew Research Center, 49% of U.S. eaters believe genetically modified foods are bad for their health.
But there are now different ways in which foods can be genetically modified. CRISPR is an ultra-precise way to make tiny changes, like inserting, deleting, or substituting individual “letters” in an organism’s DNA. In contrast, more traditional forms of genetic engineering — which create the genetically modified organisms (GMOs) that cause so much controversy today — is generally less precise, and it allows for genetic material from a different organism to be inserted into a genome, which is what gives many critics pause. (Technically, organisms edited using CRISPR are also GMOs; the term is widely panned by scientists.)
Oatley and his team didn’t use CRISPR to add genetic material from a different organism, he says. They made a gene edit — sterility — that is possible and probably does occur in nature.
“We just don’t screen millions of animals looking for them,” Oatley says.
Plus, worries over consuming genetically modified foods is a moot point with the surrogate sire project, Oatley points out. They used gene-editing to create males for the sole purpose of not passing on their genes in the first place. Their perfectly normal progeny would enter the food stream, not the gene-edited surrogate sires themselves.
As the debate over genetically modified animals continues, goat #1962 will just have to cool his jets. He is currently not approved to be bred in a normal farm setting for food production, despite being created to help humans by doing just that.