AFTER more than a decade of research into an increasingly common and costly broiler condition known as green muscle disease, a team of poultry scientists at Auburn University has identified a blood enzyme that could give breeders a non-invasive tool to screen birds for susceptibility to the disease.
Elevated levels of the creatine kinase enzyme can signal muscle breakdown and damage. In people, high levels of the enzyme in the blood can be indicators of heart attack, muscular dystrophy, acute renal failure and other serious muscle conditions. In broilers, they indicate the development of green muscle disease, Auburn said.
Technically called deep pectoral myopathy, green muscle disease is a degenerative condition of broiler chickens' minor pectoral muscles, or tenders, that causes the muscle tissue to bruise. The discolored tissue is not discovered until processing and deboning, and then it must be trimmed and discarded, costing the U.S. poultry industry an estimated $50 million a year in losses, an announcement said.
Also of concern to the industry is the occurrence of green muscle disease in birds marketed as whole carcasses or bone-in parts because the condition is rarely detected during processing, resulting in consumer complaints.
Auburn poultry science professor Joe Hess — who, with departmental colleagues Sarge Bilgili and Roger Lien, has conducted extensive research on the disease — said the condition is caused by sudden, excessive wing flapping, especially when that occurs one to two days before slaughter.
"Green muscle disease is an exercise issue," Hess said. "If you have a house full of chickens and there's a sudden loud noise or some other environmental stressor, they're going to get scared and agitated and start flapping their wings. If it's late in the growing season, that's when the damage occurs."
During wing movement, blood flow increases to a bird's major and minor pectorals, or breast muscles, causing the tissues to swell. Even though the swelling doesn't affect the larger breast fillet muscle, the tender has a more rigid covering and is confined to a tighter space. The swelling so compresses the muscle that the blood supply is cut off and the tissue bruises.
Early in the team's green muscle research, Lien perfected a technique — "encouraged wing flapping" — to assess birds' susceptibility to the condition and determine factors that contribute to development. Using that procedure, the scientists found that broiler strains bred for higher breast meat yields are more likely to develop the disease, as are broilers marketed at heavier weights and, to some degree, male birds.
They also found correlations between temperature and disease incidence.
"When the weather is hot, broilers grow at a lot slower rate than in cooler weather," Hess said. However, "cool to normal temperatures are periods of rapid growth, and broilers that get agitated during those periods have a greater likelihood of muscle damage."
In their latest focus on the relationship between creatine kinase levels and deep pectoral myopathy, the Auburn scientists induced excessive wing activity and then measured enzyme levels one to four days after the trials.
At processing, they discovered that broilers in which levels of the enzyme had jumped significantly post-flapping were far more likely to have muscle damage to the minor pectorals, leading them to conclude that encouraged wing flapping and creatine kinase levels could be used as tools in genetic selection programs to screen for green muscle disease susceptibility, the university said.
That is good news to Randall Ennis, an Auburn poultry science alumnus who now serves as chief executive officer for the chicken division of Aviagen Group International, the largest poultry breeding company in the world. Through a comprehensive network of global, wholly owned locations and distributors, Aviagen delivers day-old breeder chicks to more than 250 poultry companies in more than 100 countries.
"We always are evaluating and looking for different tools, such as identifying genetic markers, to make our program more efficient and allow our customers to realize genetic progress faster," Ennis said.
Whole wheat turkey
Recent work by a research group in Poland indicates that turkey diets supplemented with moderate levels of wheat — either ground and pelleted or as whole grain — enhanced the bird's gastrointestinal function, which helps improve feed conversion. The researchers also observed additional benefits attributable to wheat supplementation, including an increase in gizzard weight and a significant reduction in gizzard pH.
The group authored an article summarizing its findings, "Gastrointestinal Morphology & Function in Turkeys Fed Diets Diluted with Whole Grain Wheat," which appeared in a recent issue of Poultry Science, a journal published by the Poultry Science Assn. (PSA).
The lead author, Dr. ZenonZdunczyk, is a professor at the Institute of Animal Reproduction & Food Research, Polish Academy of Sciences. He was joined in the study by researchers in the department of poultry science and the department of histology and embryology at the University of Warmia & Mazury in Olsztyn, Poland.
The complete article is available for download at http://ps.fass.org/content/92/7/1799.
"In recent years, one view that has gained popularity is that feeding a larger particle size and whole grain to poultry improves gizzard function and overall bird health. The aim of our study was to verify a part of this hypothesis, namely that moderate dilution of complete turkey diets with whole wheat — we examined levels up to 22.5% — would improve gastrointestinal function and, hence, contribute to growth performance. Our findings indicate that this is the case," Zdunczyk said.
Approach and findings. In the study, 900 male BIG-6 turkeys were randomly assigned to five dietary treatments: a basal diet, a basal diet diluted with low levels of ground and pelleted wheat or whole wheat or a basal diet diluted with high levels of ground and pelleted wheat or whole wheat. At successive stages of the experiment, the dilution levels of wheat ranged from 5% to 22.5%.
The 180 male turkeys in each group were studied from five to 18 weeks of age. They had free access to feed and water and were kept in pens on litter in a building with a controlled environment.
The trial lasted for 126 days, with the birds weighed at the beginning of the experiment (at 29 days of age) and at the end of each feeding period — on days 56, 84 and 126. Bodyweight gain and feed conversion ratio were calculated for each period.
The results of the experiment indicated that moderate dilution of a basal diet with wheat does not reduce the final bodyweight of turkeys and that the use of whole-grain wheat improves their physiological parameters and growth performance. Supplementation of the birds' diets with whole wheat improved feed conversion as a result of improved gastrointestinal tract function, i.e., lower pH of gizzard digesta, and other parameters characterizing the physiology of the small and large intestines.
Potential commercial implications. While the work was carried out in Europe, it potentially has implications for turkey producers in the U.S., according to PSA president Dr. Michael Smith.
"Turkey production is an important poultry enterprise throughout the world, with regional ingredient availability and varying cultural preferences often resulting in significantly different rearing practices in various markets. Some of the strategies turkey researchers are pursuing — including those discussed in Dr. Zdunczyk's group's paper — may help producers address these differences," Smith said.
Chickens could be the unexpected beneficiaries of the growing biofuel industry if fed on proteins retrieved from the fermenters used to brew bioethanol, thanks to research supported by the U.K.'s Engineering & Physical Sciences Research Council (EPSRC).
It has long been known that the yeasty broth left over after bioethanol production is nutritious, but it has taken a collaboration between Nottingham Trent University and AB Agri, the agricultural division of Associated British Foods, to prove that yeast protein concentrate (YPC) can be separated from the fibrous cereal matter.
The researchers have also shown that YPC may be a cost-competitive substitute for imported soybean meal-based feed and similar high-value protein feeds currently used in the diets of chickens bred for meat production.
The project was borne out of the vision of biofuel pioneer Dr. Pete Williams of AB Agri, who believed that valuable material was being overlooked when cereals were fermented to make bioethanol.
He and Dr. Emily Burton of Nottingham Trent University were able to secure funding from EPSRC for a CASE studentship that allowed them to develop and analyze the process.
To establish the nutritional value of the concentrate, EPSRC CASE student Dawn Scholey examined the composition of the newly isolated, patented YPC in a series of experiments, which showed that it can be readily digested by chickens. A paper outlining this research was published in a recent edition of Food & Energy Security.
Burton said the work is only just beginning. "Bioethanol is already a 60 billion liter per year global market, but this project shows the fuel itself is only half the story; immense value lies within other co-product streams, too. As well as the proteins, the yeast content provides important vitamins and other micronutrients," she said.
The patented process separates dried distillers grains plus solubles into three fractions — fiber, a watery syrup and YPC — allowing global production of almost 3 million metric tons of supplementary high-quality protein per year alongside the current levels of bioethanol produced. A project at a U.S. bioethanol facility is now up and running to demonstrate the performance of the process at the factory scale.