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Monday, August 1, 2011

Foot Rot in Beef Cattle

John F. Currin, D.V.M. and W. Dee Whittier, D.V.M., Extension Veterinary Specialists, Virginia Tech, and Nancy Currin, D.V.M., Veterinary Extension Publication Specialist, Virginia Tech
Causes of Foot RotID
Authors as Published

The primary infectious agent for foot rot is Fusobacterium necrophorum, which is an anaerobic bacterium. Anaerobic bacteria will only grow in the absence of oxygen. This bacterium is commonly found in the environment. Other bacteria such as Bacteroides melaninogenicus, Staphlococcus aureus, Eschericia coli, and Actinomyces pyogenes will increase the virulence of F. necrophorum and, therefore, increase the incidence and severity of disease. F. necrophorum can be isolated on nondiseased feet, as well as in the rumen and feces of normal cattle. Therefore, it is necessary for there to be an injury to the skin and underlying tissues between the toes for the bacteria to gain entrance and cause disease. Injury is often caused by walking on abrasive or rough surfaces, stony ground, sharp gravel, hardened mud, or standing in a wet and muddy environment for prolonged periods of time. High temperatures and humidity will also cause the skin to chap and crack, leaving it susceptible to bacterial invasion. Calves are the more susceptible to the disease than cows or bulls. Mineral deficiencies of zinc, selenium, and copper seem to increase the incidence of disease.
Prevention is a very important aspect of this disease, and the major focus is to ensure good health of the foot. Rough areas should be smoothed or fenced off from cattle, and debris should be cleared. Sharp gravel should be replaced with smooth stones. To keep cattle from standing in wet, muddy conditions, barnyards should be scraped frequently, and measures to improve drainage should be taken.
Zinc is important in maintaining the integrity of the skin and hoof. In a three-year study, feeding 5.4 gm of zinc methionine per steer daily (added to a free-choice mineral supplement,) decreased the incidence of foot rot, and increased daily gain in grazing steers. Feeding organic iodide (EDDI) at 10 to 15 mg per head per day has been helpful in decreasing the incidence of foot rot on some farms (Maas). Consult with your veterinarian and/or nutritionist when deciding about adding a zinc or organic iodide supplement.
There is a vaccine available that targets the bacteria F. necroforum. This vaccine may be helpful in reducing the incidence and severity of disease, but appears to be the most effective and economical in the feedlot or other intensive rearing situations. Good management programs, including mineral supplementation and vaccination programs increase the overall immunity of the cattle, thereby making them less susceptible to disease.
Foot rot is a major cause of lameness in cattle and can have a great economic affect on a farm. It is a disease of the skin and other tissues between the toes of all classes of cattle. Swelling and moderate to severe lameness accompanies the condition. Prevention and early treatment, along with good overall management programs, are essential to decrease the incidence and economic effect of the disease.

The following is a letter from Dr. Jan Shearer used with his permission:  (Concerning Footrot)
Foot Rot
It has been a very wet summer. Moisture and mud are important predisposing causes of problems with foot rot.  It softens the interdigital skin which makes it more vulnerable to injury thus leading to a greater incidence of foot rot.  Foot rot also tends to occur in epidemic proportions - seems that cows in early  lactation are often particularly susceptible.  So, a couple of thoughts: 
1) As much as is possible try to move feeders to cleaner drier ground when possible during those times of the year when it is wetter.  Keeping feet cleaner should help reduce incidence.
2)  Use the feed through tetracycline crumbles when you get into these herd outbreak conditions. 
3) Try to treat affected animals early so that you reduce the contamination in the environment and avoid complicated problems in affected cows. 
 The organisms are usually quite susceptible to most antibiotics so that early treatment is more important than drug selection. There are other contributing causes to foot rot such as corns (callouses between the claws) and conformational factors that contribute to a greater tendency toward foot rot problems.  I have also observed that foot rot becomes a problem in herds for no apparent reason, several cases occurring in 1 year and none the next.
4) Keeping cows in good body condition and supplemented with appropriate trace minerals and biotin in rations is helpful. 
5) Lime has been used for many years to combat the problem.  I am sure that it doesn't hurt but I am not sure that it will solve the problem either.  I don't think I have ever seen any studies on use of lime to control this problem, but it won't hurt to use some to alter the pH of the environment. It is a stubborn problem at times.  Fortunately, it is treatable when you identify it early.

Dr. Jan Shearer- Professor at Iowa State University.