When looking for leaner meats, consumers often turn to poultry options, like chicken and turkey.Gale Strasburg, professor in the Michigan State University (MSU) Department of Food Science and Human Nutrition, was awarded a three-year, $500,000 grant from the U.S. Department of Agricultural National Institute of Food and Agriculture (USDA NIFA) to investigate how external temperature affects breast muscle development in turkeys, with an eye on minimizing fat content for these lean meat options.“Heat or cold stress can change the amount of fat that's deposited in the breast muscle in the turkey hatchling,” said Strasburg. “We always think of poultry products as being very lean, and consumers buy them, particularly the breast meat, for their leanness. If you get undue deposition of fat within the muscle itself, it's considered undesirable, by both consumers and the industry.”
Temperature can also affect other qualities.“Sometimes, you end up with some necrosis, or death of muscle cells, and some disorganization of the muscle that leads to poor water-holding. That can cause meat to be less juicy, less flavorful and change its texture,” Strasburg said. Strasburg is working with A. Daniel Jones, professor in the MSU Department of Biochemistry and Molecular Biology; Sandra Velleman, professor in the Ohio State University (OSU) Department of Animal Sciences; and Kent Reed, professor and interim vice chair of the University of Minnesota’s College of Veterinary Medicine, to determine how exposure to hot and cold environments can impact a turkey’s breast muscle growth and development.
Strasburg is particularly interested in how temperature affects turkeys immediately after they hatch. To do this, he will examine satellite cells – cells that are active during embryonic development and up to two weeks after a turkey hatches. Poultry breeding company Aviagen will supply turkey eggs.
“Satellite cells are very susceptible to heat or cold temperatures, and that, in turn, affects long-term muscle growth and development,” he said.
This research builds on a previous USDA NIFA project of Strasburg’s.
In that project, Strasburg and his collaborators examined the effects of heat and cold stress in two turkey breeding lines. One line, maintained at OSU, was a random-bred line representing the turkey of 1967. The other line, called the fast-growling line (F-line), took the random-bred line of the 1967 turkey and selected it for only one trait: body weight at 16 weeks of age. The goal of the grant was to compare the responses to heat or cold stress of the slower-growing turkey of the 60s with that of a fast-growing line.
For Strasburg’s last grant, fertilized turkey eggs from both random-bred and F-lines were brought to MSU and placed in an incubator. After 28 days, the eggs hatched and were immediately divided into three groups and placed on different shelves in a brooder, a unit that measures constant temperature and delivers food and water. One group was brooded at the industry-standard temperature of 35 degrees Celsius (95 degrees Fahrenheit), one was brooded at a hotter temperature (39 C/102 F), and the other was brooded at a colder temperature (31 C/88 F).
“These temperatures were chosen to model warmer or cooler temperatures that turkey hatchlings might be exposed to when they are transported from a hatchery to growing facilities,” said Strasburg.
The previous grant did not include turkeys bred for commercial production — birds whose meat is purchased by consumers.
“Our new grant focuses on the next step in this study, where the actual birds are used commercially,” Strasburg said. “We're still doing comparisons between these birds and the random-bred bird of the 1960s, but this new funding allows us to extend that study to birds the industry currently uses for meat.”
With their most recent funding, Strasburg and his team will examine gene expression to determine if heat and cold stress affects turkey breast muscle growth and development in different ways.
“In the previous study using random-bred and F-line birds, the two lines responded to heat and cold stress in different ways, so that's why we think it's really important now to look at the commercial birds, to see how genetic selection for growth, as well as these other traits, will impact tolerance of the birds to heat or cold,” he said.
The turkeys used for this research will be hatched and housed at the MSU Poultry Teaching and Research Center. Strasburg will be collecting muscle samples from turkeys exposed to warm, cool or standard temperatures at different stages of growth. Strasburg and Jones will examine these samples for changes in metabolite levels. Metabolites are small molecules that aid in converting protein, fats or carbohydrates into energy.
“By measuring metabolite levels in muscle, we are able to get a detailed snapshot of the physiological state of the birds in response to different temperature conditions,” Strasburg said.
In addition, Velleman will analyze the samples for changes in muscle structure, while Reed will investigate changes in gene expression and novel compounds, called circular RNAs, which result from exposing newly hatched birds to different temperatures.
“This research will benefit the global turkey industry by providing informed recommendations for turkey breeders and growers for efficient production of high-quality meat products.” Strasburg said.