Unlocking the Secrets of Climate-Smart Sheep
Zaira Estrada-Reyes, Ph.D., an assistant professor of animal genomics at N.C. A&T, checks on some of her Florida Cracker sheep at the University Farm recently.
The Florida Cracker sheep is a survivor.
Descended from the sheep brought to North America by the Spanish in the 16th century, this mid-sized breed thrived in the pastures and piney woods of Florida. For four centuries these feral sheep foraged in the wild for food, dodged alligators and bobcats, and endured the ranchers who rounded them up twice a year to shear them of their wool.
Along the way, Florida Cracker sheep developed via natural selection a tremendous resistance to heat and parasites — two key genetic characteristics that could strengthen modern sheep breeds.
“The sustainability of sheep operations depends on the ability of animals to efficiently produce goods, such as meat or wool, without overexploitation of existing resources while also maintaining adequate health and overall performance,” said Zaira Estrada-Reyes, Ph.D., an N.C. A&T State University professor who’s investigating the breed. “However, because of global warming, heat stress is one of the main limiting factors of sustainable sheep production.”
Estrada-Reyes has been studying sheep since she was a university student in her native Mexico. As a doctoral student at the University of Florida, where she earned her Ph.D. in animal molecular and cellular biology, she received grant funding from the U.S. Department of Agriculture’s Sustainable Agriculture Research and Education program to identify genetic markers associated with parasite resistance in sheep and goats. It was during her doctoral studies that Estrada-Reyes was introduced to the Florida Cracker sheep.
Makenzie Harrison, an Undergraduate Research Scholar working with Reyes, takes a look at a Florida Cracker sheep using infrared software to see how the heat is affecting the flock.
“I think this breed is fantastic,” said Estrada-Reyes, an assistant professor of animal genomics at N.C. A&T. “It’s endangered, so conservation efforts are critical. Also, the Florida Cracker has unique characteristics, such as high thermal tolerance and parasite resistance, but we don’t have a lot of research on it. Climate change is having a tremendous effect on livestock populations, and it’s up to us as researchers to try to find solutions and incorporate this knowledge into building sustainable sheep operations.”
Since joining the faculty of N.C. A&T’s College of Agriculture and Environmental Sciences in 2021, Estrada-Reyes has been working on two separate grant-funded projects to unravel the complicated genetic structures that have given rise to desirable traits in this special breed of sheep.
One project is an investigation of the inherited and epigenetic mechanisms that make Florida Cracker sheep resistant to Haemonchus contortus, a common gastrointestinal parasite that can cause weight loss, anemia and even death in sheep. Also known as the barber’s pole worm, H. contortus poses a significant threat to sheep — especially for pregnant sheep and lambs as they are weaned — because it thrives during hot and humid weather.
If researchers can identify the genetic markers and epigenetic components associated with resistance to this parasite, Estrada-Reyes said it might be possible to cross-breed these traits into other sheep breeds. Sheep that are genetically resistant to parasites can grow larger, produce more meat and can make sheep operations more profitable and sustainable.
This project is being funded by a Evans-Allen capacity grant of $688,178 from the USDA’s National Institute for Food and Agriculture.
Graduate student Sola Ikuejamoye Omotore examines some of the Florida Cracker sheep at the University Farm as he feeds them recently.
Estrada-Reyes also is researching how heat-related stress in sheep might compromise their immunological responses against pathogens that could further affect their size, weight and overall health. She’s gathering data from rectal thermometers, blood draws and non-invasive infrared thermal imaging that show how high heat and humidity can affect sheep.
This project — funded by a $100,000 grant from the 1890 Universities Foundation — is using “machine learning” to foresee when sheep are being stressed by heat. Ultimately, Estrada-Reyes said, she would like to build a mobile app to alert ranchers of impending heat stress so they can cool their sheep sooner.
“Our goal with the algorithm is to see if we can predict heat stress,” Estrada-Reyes said. “We want to provide an understanding of the physiological, behavioral, hematological and immunological responses to heat stress.”
Today, the Florida Cracker breed is experiencing a different kind of stress: potential extinction. As the sheep industry during the 20th century turned to more standardized breeds of larger sheep that produce more wool and meat, interest in the Florida Cracker sheep waned. The Livestock Conservancy now lists this breed as critically endangered. It’s estimated that there are fewer than 1,000 Florida Cracker remaining, including the small flock that Estrada-Reyes keeps on the N.C. A&T University Farm.
Estrada-Reyes said it’s important to preserve this breed — and to unlock its genetic secrets that can strengthen other sheep breeds.
“Heat stress in sheep is likely to be exacerbated by rising global temperatures,” Estrada-Reyes said. “I believe that an effective strategy to meet this challenge is to understand the impact of heat stress on physiological, behavioral and immunological responses to develop assessment and control measures. Research into Florida Cracker sheep has so much to offer sheep producers because this breed has such terrific characteristics.”
