Makenzie Harrison: Feeling the Heat with Historic Sheep
Harrison checks a sheep’s blood work as part of her experiment. “The highlight so far has been being able to … work with Dr. Reyes in her lab,” she said.
Makenzie Harrison had plans to travel a straight path to veterinary school when she enrolled in the College of Agriculture and Environmental Sciences’ animal science program in 2021. But, during her four years as an undergraduate, her attention shifted, thanks in part to the Undergraduate Research Scholar Program and a unique breed of sheep.
“Originally, I came to N.C. A&T thinking that I would want to go to vet school right after,” Harrison said. “However, through my classes, my mentor and my advisors, I was exposed to the wide world of agriculture, animal science and research – and I found that research was what I wanted to do instead.
“I was already working under Dr. Estrada Reyes in her lab and with her sheep at the farm when I landed on this project,” she said.
Harrison’s mentor, Zaira Estrada Reyes, Ph.D., assistant professor of animal genomics, invited Harrison to her lab in 2022 and recommended that she apply to the Undergraduate Research Scholars Program to give her an opportunity to deepen her research skills. Harrison was accepted in spring 2023 and began collaborating on a new project focused on the effects of heat stress on Florida Cracker Sheep.
One of the oldest sheep breeds in North America, Florida Cracker sheep may have first been brought to Florida by Spanish conquistadors, and are uniquely adapted to hot and humid tropical conditions. However, the breed is also critically endangered, according to The Livestock Conservancy; once popular, it became overlooked as markets shifted to larger breeds with more wool and meat in the 1940s.
Now, its resistance to parasites and ability to tolerate humid conditions are putting the breed back on the radar, particularly as many livestock breeds struggle with hotter temperatures in the face of climate change.
“Heat stress reduces an animal’s feed intake and digestive capacity, which compromises its nutrient absorption and metabolism,” Harrison said. “Additionally, their respiration rate increases and induces oxidative stress. It’s a major concern for sustainable sheep production in the Southern U.S. due to comparatively warmer climates.
Makenzie Harrison, right, and her mentor, Zaira Estrada-Reyes, are working to mitigate heat stress in sheep. The Florida Cracker Sheep that they are holding have an unusually high tolerance to heat and parasites, making them one of the hardiest breeds.
“Through this project, we’re hoping to find a strategy to mitigate heat stress for more sustainable sheep production so farmers in the Southern U.S. will be able to better know how to care for their sheep and avoid many of the problems that come with heat stress, such as daily weight gain and reproductive issues.”
In summer 2023, the student and professor tested 14 ewes for six weeks in heat and cooling conditions. Seven of the sheep were exposed to regular, ambient temperatures, while the remaining seven were placed in a pen with an evaporative cooling fan. Each week, Harrison and Reyes took respiration rates, rectal temperatures, blood samples, and thermal imaging from both groups.
“Our findings showed that short-term heat stress alters the hematologic (overall blood health) and metabolomic profile (the study of small molecules within cells, tissues, biofluids and organisms) of the sheep,” said Harrison. “Heat stress weakens their immune system. However, further research is needed to compare Florida Cracker to other sheep breeds.”
The results of Harrison’s project were published in two articles in Oxford Academic’s Journal of Animal Science in Sept., 2024. Reyes said she wasn’t surprised.
“Since she’s been in my lab, she has not stopped working,” said Reyes. “I’m really happy with her performance, and I’m very happy with her working with my graduate students as well. She’s hard-working, responsible, and one of the best Undergrad Research students that I’ve had under my supervision.
“Having two articles published as an undergraduate student is a huge accomplishment.”
Harrison’s her time at N.C. A&T has been a “comfortable journey.”
“Everyone in my department has been very welcoming and encouraging,” said Harrison. “The highlight so far has been being able to come out to the University Farm and work with animals, and to work with Dr. Reyes in her lab.”
