A study, sponsored by the US Poultry & Egg Association, was conducted into the occurrence of Green Muscle disease in broilers by researchers from Auburn University.

Green Muscle Disease (GMD), or Deep Pectoral Myopathy, is a necrosis of tender muscles in poultry, explain its authors, Drs Roger J. Lien, Joe B. Hess and Sarge F. Bilgili. Lesions may affect one or both tenders in broilers and cause a marked red, purple or green discoloration that results in their condemnation.

Because tenders lie in rigid compartments defined by the keel and fillet, and are contained in tough fascia, their normal expansion during exercise is reduced, causing swelling that impairs blood flow. GMD is not due to injury during broiler catching or slaughter; rather, it is influenced by wing flapping a few days to weeks earlier.

This project's objectives were to:

1. provide a pictorial aid for determining when factors that induce GMD in broilers in the field are actually occurring.
2. determine effects of lighting programs and ramps that induce greater activity levels on GMD susceptibility.
3. determine if migration pipe climbing or periodic light intensity increases during disturbance by caretakers increases GMD occurrence, and
4. evaluate the impact of typical US and European lighting programs on GMD susceptibility.

The induced wing flapping method was used to stimulate GMD in broilers at intervals prior to slaughter. Images of typical lesions were characterised on colour posters distributed to processing personnel to aid in determining the timing of field GMD induction and facilitate its prevention.

Broilers were reared under different lighting programme, with or without ramps between feeders and drinkers to accentuate or inhibit activity levels.

Ramps and lighting programmes designed to increase activity levels inconsistently reduced GMD, suggesting that activity levels are not primary factors determining susceptibility. Broilers forced to climb over migration pipes did not have an increased incidence of GMD.

However, periods of brief increased light intensity coupled with human disturbance increased GMD and indicates that how caretakers conduct their daily checks of broilers may influence the occurrence of GMD.

Broilers were reared under European lighting programmes providing higher light intensity and longer periods of darkness, and a US programme providing less darkness and light intensity. Differences in GMD due to lighting programmes were inconsistent, suggesting that they also are not a primary factor influencing the occurrence of GMD.

If use of the posters and changes in bird checking reduced GMD incidence 20 per cent in Alabama alone, it should be worth an estimated $1.25 million annually to the industry, concluded Lien and co-authors.

November 2010