The Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) has a rich history. Over the 50 plus years we have existed, TVMDL professionals have worked tirelessly to provide the most accurate and up to date resources to our clients. The following excerpt is part of an ongoing series of articles written by TVMDL’s first director, Dr. William Sippel, and other professionals from the earlier days of TVMDL. Some articles were written for features in The Cattleman publication where others were case studies over recent diagnoses. We hope you enjoy this look back on TVMDL’s history.
Veterinary Outlook: Bermuda Grass Emphysema
William L. Sippel, V.M.D
Emphysema is a condition of the lungs marked by escape of air into the lung tissue, constricting of the air passages, and preventing proper flow of air in and out of the lung. The disease is known by a variety of other names including pulmonary adenomatosis, bovine asthma, panting disease, fog fever, proliferative pneumonia and others. It is very similar to heaves of horses and emphysema of humans. The condition has been recognized for many years but seems to have become more prevalent recently. It is seen in cattle year-round and under a variety of husbandry conditions. One type of the disease is much more frequent in Texas from early May through early July. This type is seen 2-14 days following turning cows into lush, young Bermuda grass. We often have dry weather in April followed by rains in early May. Under these conditions Bermuda grass comes on with rush and large numbers of cattle can become affected with pulmonary emphysema.
The condition has been recognized around the world and has many characteristics of an allergic manifestation. The onset is usually sudden and characterized by difficulty in breathing. The chin will be elevated in order to straighten out the air way. A slight amount of foam may form around the mouth and nostrils. Older cattle are more frequently affected than young animals, lending support to the theory that it is of an allergic nature inasmuch as young cattle have not yet had time to become sensitized.
One of the theories regarding the case of the condition is that a breakdown product of an amino acid, tryptophan, causes the reaction in the lung. The condition has been produced experimentally with this agent. Mold growing on sweet potatoes has been incriminated as a cause and mold on the tips of the blade of Bermuda grass has been suspected of causing emphysema. However, due to the variety of conditions and agents associated with pulmonary emphysema it is likely that there are multiple causes.
Affected animals have great difficulty in getting enough air and walk slowly and carefully. Any over-exertion will result in an oxygen deficit and death. The small sacs in the lungs, where transfer of oxygen and other gases to the blood stream takes place, become filled with fluid and cellular debris so that the function of the lungs is severely impaired.
About 5-10% of a herd may be affected and a high percentage of these animals die. Upon opening the chest cavity of an animal dead from this disease, the lungs fail to collapse. They appear large and feel “foamy.” Animals that die in the early acute stages have less air and more fluid in the tissues making the lungs feel unusually heavy.
The first thing that should be done when the disease occurs is to remove the cattle from the offending forage, which in May will probably be Bermuda grass. These animals should be “eased” out of the pasture as opposed to driving them in a normal manner. Dogs should definitely not be used. The animals will prefer to move very slowly and will be easy to drive if not hurried. They handle best if worked down a fence row to the gate. Cattle with advanced cases will die from lack of oxygen if forced to move too fast. Whenever possible the cattle should be put in a holding pen, away from Bermuda grass, and fed hay and grain. In treating this condition veterinarians use large doses of atropine, antihistamines and antibiotics. Remarkable recoveries can occur if the animals are treated early enough in the course of the disease but treatment is usually ineffective.
If animals are on lush, young Bermuda grass, the possibility of this disease should be born in mind and the cattle watched closely. When the first signs appear, the entire herd should be removed from the pasture. It might be possible to utilize the pasture if the cattle are first allowed access to hay or grain in order to be partially full before going into the pasture. Is is possible for additional cases to appear under this stem but the number of cases should be low. If no other pasture is available, a temporary fence should be thrown around a minimum amount of the field so that the Bermuda grass contained therein will be consumed in a short time. The animals can be fed in this restricted area.
After the Bermuda grass matures fewer cases of the condition appear and the grass can usually be grazed without additional cases occurring.
The various varieties of Bermuda grass have been a great boon to the cattle industry and ranchers should attempt to manage their cattle in a manner that will enable them to utilize this valuable forage. As mentioned above, the condition appears year-round on a variety of forages including purple mint (Perilla frutescen) in northeast Texas, moldy hay, silage, corn stalks, hegari, milo, and others. Toxins associated with enterotoxemia have been postulated as the cause of emphysema. Molded peanut or soybean hay or other types can also cause the condition.
Unless one has had repeated occurrences of this disease in certain pastures, probably the most practical procedure is to watch cattle on lush, young Bermuda grass closely and take action as outlined above if cases appear. Unfortunately, there is no vaccination or desensitization for this disease.