The Mid Atlantic Poultry Farmer a supplement to the Delmarva Farmer

Researchers studying wooden breast meat syndrome


(Editor’s note: Daniel Bautista is director of Lasher Laboratory 
at University of Delaware.)

(March 2017) — Broiler chicken meat production and consumption has reached record levels in the United States and it is soon projected to surpass pork and become the most consumed animal protein globally.
Broiler chickens have been successfully bred for fast and efficient growth, improved breast meat yield and lean muscle deposition.
The preference for breast meat by the U.S. consumers have led to a steady increase in market weights of broiler chickens with high breast meat yield.
This coincided with the emergence of breast meat abnormalities of broiler chickens — wooden breast, white striping and deep pectoral myopathy, causing significant breast meat quality downgrades.
That’s a big concern in the U.S., which is a world leader in chicken meat production, and worldwide, where chicken is a major, high-quality source of animal protein.
These three conditions are not associated with infectious agents, nor do they present a threat to food safety, according to a new report by the American Association of Avian Pathologists.
All three breast meat disorders have been seen in all breed crosses of broiler chickens as early as two weeks of age, with varying prevalence under a wide-range of slaughter weights, management, feeding and rearing systems.
The exact cause or causes of these conditions have not yet been clearly identified.
However, inadequate blood supply to the tissues — which may result from sudden exertion, overstretching and/or compression — as well as a lower rate of blood supply and a decline in metabolic waste-product removal (carbon dioxide and lactic acid) from the muscle fibers are “likely to be involved,” AAAP said.
University of Delaware researchers are working to solve this problem. They’ve been analyzing the genetic basis involved in wooden breast and related muscle disorders.
They have determined the unique biochemistry of the hardened breast tissue.
Such findings are expected to help advance new diagnostics and treatments for the disorder.
The research group is led by Dr. Behnam Abasht, assistant professor in the Department of Animal and Food Sciences at UD College of Agriculture and Natural Resources.
Birds afflicted with wooden breast are easy to identify, even in live birds.
“The disease manifests itself exactly as the name implies, making a chicken’s breast meat tough and chewy” Abasht said.
He and his team looked at the problem was by studying the genes responsible for breast muscle development to understand the underlying biological mechanisms contributing to the disease.
By analyzing DNA information from normal versus affected versus breast muscle samples from a line of commercial broiler chickens, Dr. Abasht and his team discovered that there is lower oxygen concentration in the affected tissues.
There are also indications of oxidative stress — when free radicals build up and there aren’t enough antioxidants to detoxify them — as well as an increase in calcium in the tissue cells.”
Supplementing poultry diets with vitamin C, a potent antioxidant, may help lower the incidence of the disorder, Abasht said, and is the subject of future research. Using a subset of the genes found in the previous study, the team evaluated 204 genes in 96 broiler chickens.
From a list of 30 genes that were the most important in separating the chickens into groups of unaffected, moderately affected and severely affected, the team identified six genes that are increased in moderately to severely affected birds when compared with unaffected birds.
These biomarkers can now be used to accurately classify commercial chickens with or without the disease for the purpose of breeding out this undesirable trait.
The researchers also found that affected breast muscle possesses a unique metabolism reflecting elevated fat levels, muscle degradation and altered use of glucose.
These findings offer new insight into the biochemical processes that contribute to tissue hardening.
“This work will directly impact the health and well-being of over 500 million broiler chickens raised in the Delmarva region each year,” said Erin Brannick, director of the CANR Comparative Pathology Laboratory, assistant professor in the Department of Animal and Food Sciences and a veterinary pathologist who was a collaborator on the research. “It truly underscores the purpose of the land grant institution to apply cutting-edge research techniques to real-world agricultural problems.”
The National Chicken Council recently announced funding of more than a quarter of a million dollars on four separate research projects at independent universities and USDA’s Agriculture Research Service to understand the root cause of this muscle condition.
Extensive research is also underway to determine the non-genetic factors in the etiology of wooden breast disorder such as flock management, environment and nutritional programs.