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Protecting Your Flock – What You Need to Know about MG & MS

MG (Mycoplasma gallisepticum) and MS (Mycoplasma synoviae) are both common bacterial infections that affect chickens, turkeys, and other avian species. Found most often in backyard flocks or multi-age commercial layer operations, MG and MS can result in severe economic losses due to slow growth rates in broilers or diminished egg production in layers.

MG, also known as chronic respiratory disease (CRD) attacks the respiratory system of infected birds and can weaken their immune systems, making them more susceptible to other infections. MS can also affect the respiratory system of infected birds, but another form of the disease attacks the joints.

Signs of Infection

Chickens infected with MG may show no signs of infection, especially if there is no accompanying secondary infection. Common signs of infection include sticky discharge from the nostrils, foamy discharge from the eyes, and swollen sinuses. Often the air sacs in the lungs become infected, resulting in rales (rattling sounds) and sneezing. Affected chickens may fail to grow and gain weight or have poor egg production.

Chickens infected with MS that affects the joints will develop lameness which is followed by a reluctance to move, swollen joints, stilted gait, weight loss, and general lethargy. Those infected with the respiratory form of MS show signs of respiratory distress, similar to an infection with MG. In fact, according to Mycoplasmas in Poultry, “It is not possible to distinguish between MS and MG without administering a blood test.”


Both MG and MS are fragile organisms that cannot survive more than a few days without a host, but these diseases can be spread to offspring through eggs or through natural breeding with an infected mate. Sick or recovering birds can also spread infections through nasal or eye discharge or fecal matter to other birds in the flock. Once infected, chickens are carriers of these diseases for life, though they may not show symptoms until they are stressed.

MG and MS can also be carried by humans when egg flats, cages, coops, tools, equipment, or clothing have been contaminated with respiratory secretions or droppings from infected birds. Wild birds or rodents can also carry the infection and spread it to the flock.

MG & MS Prevention

Start with Disease-Free Birds

The best way to control MG and MS is to begin your flock with disease-free birds, then practice scrupulous biosecurity to protect your flock. Chicks should always be purchased from MG or MS-free flocks. Care must be taken to avoid purchasing adult birds with unknown MG or MS status.

Minimize Contact with Other Flocks

Be sure to change your clothing and footwear if you have visited other birds before coming in contact with your own flock. Also be sure to thoroughly clean and disinfect tools and equipment when they’ve been used in other areas of the farm or in the vicinity of other flocks. You may also want to use a set of dedicated tools and equipment for each flock to avoid contamination.

Keep Rodents & Wild Birds Away

Institute a pest control plan to keep rodents and wild birds away from your flock. Both rodents and wild birds can carry the disease and infect your birds.

Boost Immunity with the Right Diet

Using quality feed and adding fresh garlic or apple cider vinegar to food and water can boost immunity, making birds less susceptible to infection.

Quarantine New Birds

Be sure to quarantine any new members of the flock at least 12 yards away for a minimum of 4 weeks in order to avoid infecting your flock.

MG & MS Treatment

While antibiotics can be used to treat infected birds and eliminate clinical symptoms, treated birds will still be carriers of either MG or MS. The most common antibiotics for treatment include Tylan, Baytril, and Gallmycin.

In order to completely eliminate MG or MS, it is necessary to harvest or cull infected broilers. Layers are often eliminated at the end of their laying cycle. Complete disinfection, followed by a rest period is recommended before establishing a new flock.

Many commercial operations maintain an all-in, all-out policy to prevent problems with MG or MS infections.

While both MG and MS are not usually life-threatening to your flock, these infectious diseases can limit the productivity of your chickens, resulting in losses from slow growth and poor egg production. That’s why it’s so important to start your flock with healthy birds, practice solid biosecurity, and always quarantine new additions appropriately to avoid infecting your flock.

If you’re looking for a source of healthy broilers or layers, be sure to check out the NPIP certified chicken hatcheries at Freedom Ranger Hatchery. We provide quality baby chicks shipped direct to your door, nationwide!