The rains have come, the pastures look great, and the stockers seem full and content. But, today you notice one animal lying down when all the others are up and grazing.
As you approach, the calf gets up and moves away but is dead lame on the right rear leg. On closer inspection, you note that just above the hoof seems swollen, the toes are separated and the area between the toes appears reddened. You may have your first case of foot rot for the summer grazing season.
Foot rot (Necrotic Pododermatitis, Interdigital Necrobacillosis) is one of the most common causes of lameness in cattle. But, it's also arguably the most misdiagnosed and overdiagnosed lameness in cattle.
There Are Many Causes There are many causes of lameness. Not every limping calf has foot rot. Fortunately, the signs of foot rot are pretty characteristic. Unfortunately, ruling out all the other causes of lameness requires that you restrain the calf and pick up the foot.
Correctly diagnosing foot rot is more than just an academic exercise. Lack of response to treatment is often due to misdiagnosis. Even more economically significant is the calf who has a lameness due to a condition in which timely marketing could salvage much of the calf's value. If we are in the habit of treating all lameness as foot rot, antibiotic withdrawals will prevent us from being able to salvage the calf.
But, let's assume you've carefully examined the foot and didn't find any wires, nails or other reasons for the lameness. You noted a characteristic odor, and it seems the calf has a bona fide case of foot rot. Why does this disease occur, and what are the prevention techniques and treatments?
The bacteria Fusobacterium necrophorum and/or Bacteroides melaninogenicus cause foot rot in cattle. These bacteria are common in the environment and F. necrophorum is present in the rumen and feces of normal cattle. F. necrophorum has been shown to survive in the soil for up to 10 months.
To become infected and exhibit signs - this takes about five days - the continuity of the foot skin must be broken. This provides entry for the infectious agent that is present in the environment. When objects such as stones, plant stubble, wire, nails, and/or glass injure skin of the interdigital space - even microscopically - infection may result.
In many instances, conditions around feed bunks and watering areas are conducive to hoof injury. Exposure to manure-laden mud or water; frozen, rough ground; or extreme drought may also contribute to infection by these organisms. High temperatures and excess moisture or humidity also cause the skin between the claws to chap or crack, allowing bacteria to invade. Foot rot incidence varies with weather, season and pen or pasture condition.
Prevention Strategies Management procedures that eliminate insults to the skin between the toes will contribute to the prevention of foot rot. Two key insults are chronic exposure to wetness, such as mud, and objects that get between the toes and break the skin.
In the feedlot, good pen maintenance is key. Making sure pens are free of sharp objects such as stones or glass or frozen, muddy, rough ground will aid in preventing foot injury and infection.
Building mounds is a common preventive measure. Mounds promote drainage and give cattle a dry place to rest. Mounds should allow 10-20 sq. ft./head and be oriented to receive maximum exposure to the sun.
Feed additive preventive agents can be used in outbreak situations. Aureomycin (chlortetracycline) is labeled for prevention of foot rot in beef cattle at a dosage of 100mg/head/day for cattle over 700 lbs.
Extra-label drug use privileges (i.e., higher dosages) do not extend to feed additive drugs. Ethylene Diamine Dihydriodide (EDDI) cannot be added to feed to control foot rot, but it can be used as a nutritional source of iodine. The maximum level of EDDI in the diet allowed by FDA is 10 mg/head/day.
A variety of nutritional supplements has been suggested to affect the incidence of foot rot. To our knowledge, there haven't been published scientific reports of efficacy for these products.
Dairies use walk-through footbaths containing 5% solution of copper sulfate or 5% formalin. These procedures are cumbersome and inconvenient in most feedyards and pastures.
Volar (Bayer) and Fusogard (ImmTech Biologics) are licensed vaccines consisting of strains of F. necrophorum. Two doses are required for protection.
Medication Speeds Recovery While some cases of foot rot heal spontaneously, the spontaneous cure rate is unknown, and it's widely believed that medication speeds recovery. Approved antibiotics for the treatment of foot rot include Naxcel, Nuflor, Liquamycin LA-200 and other brands of long-acting oxytetracycline, Sulmet and other sulfamethzine boluses, sulfadimethoxine oral solution or powder, and tetracycline powder. Remember that use of Naxcel, Nuflor or any of these drugs other than according to label directions requires a veterinary-client-patient relationship along with a veterinary prescription.
If feasible, local treatment by cleaning the foot, trimming dead tissue and applying an antiseptic may be of benefit.
Treatment is optimized when an appropriate dose is given as soon as possible after discovery. If treated early, response is quick and recovery can be expected in three to four days. When treatment is delayed, recovery is significantly delayed or fails.
When foot rot fails to respond to medication and terminates as a suppurative arthritis, claw or hoof amputation may be used to correct the condition and make the animal suitable for marketing.
Louis Perino, DVM, PhD, is a professor of immunology, health and management at West Texas A&M University in Canyon. Gerald Stokka, DVM, MS, is an associate professor and Extension beef veterinarian at Kansas State University in Manhattan.