From time to time, if you follow the articles written here at all, you'll notice that we deviate from the typical feeding and management format normally covered in my articles. This issue will be one of those cases. Over the past summer, I've gotten numerous calls from clients and concerned producers regarding lameness noted in cattle they have out on pasture both cows and yearlings. Generally the statement is made that “I've got a bad foot rot problem out here. What can I do about it?” Like so many other topics of this nature there are a lot of misconceptions regarding foot rot as well as other conditions which cause lameness in cattle. In advance let me state for the record that I am not a veterinarian so I have to refer to animal health professionals for the animal health and physiological information I am about to share. One particularly helpful reference comes from Kirkpatrick and Laman (2000) from Oklahoma State University. However, there are also a number of nutritional methodologies that have a place in prevention of this condition and which, properly placed can save you a ton of money in treatment costs.
So What is Foot Rot Anyway?
In many cases, every time a cattleman sees a yearling favoring one or more of it's feet, he attributes it to foot rot. This may or may not be the case. Technically speaking, foot rot is a subacute or acute necrotic (decaying) infectious disease of cattle, causing swelling and lameness in one or more feet. The disease can become chronic, with a poorer chance of recovery the longer treatment is delayed. A delay in treatment can result in the deeper tissues of the toe(s) being affected. Weight gain is significantly reduced when grazing cattle contract the disease. In one three-year study, Brazle (1993) reported that affected steers gained 2.3 lbs. per day, while steers not affected gained 2.76 lbs. per day. Obviously if cattle are sore-footed and can't travel as well, they will not eat as well and subsequently won't gain as well.
Foot rot is usually sporatic in occurrence, but the disease incidence may increase up to 25 percent in high-intensity beef or dairy production operations. Here's the key though: approximately 20 percent of all diagnosed lameness in cattle is actually foot rot.
What's the Cause?
Mechanical injury or softening and thinning of the interdigital (between the toes) skin by puncture wounds or continuous exposure to wet conditions can provide entrance points for infectious agents. Fusobacterium necrophorum is the bacteria most often noted to cause or contribute to this problem. The majority of F. necrophorum isolated produce toxins that cause necrosis (decay) of the infected tissues. Interestingly, F. necrophorum is also isolated from liver abscesses in feeder cattle, as well as other similarly acting conditions in cattle. This bacterium appears to act cooperatively with other bacteria, thereby decreasing the amount of F. necrophorum necessary to cause disease.
How Does it Spread?
Feet infected with F. necrophorum serve as the source of infection for other cattle by contaminating the environment. There is some disagreement on the length of time F. necrophorum can survive off of the animal, but estimates range from one to ten months. Once an opening is created in the tissues, bacteria gain entrance into subcutaneous tissues and begin rapid multiplication and production of toxins that stimulate further continued bacterial multiplication and penetration of infection into the deeper structures of the foot.
What to Look for
Foot rot occurs in all ages of cattle, with increased case incidence during wet, humid conditions. In many cases, incidences seem to increase if this wet period follows a very dry period. When case incidence increases in hot and dry conditions, attention must be directed to loafing areas, which are often crowded and extremely wet from urine and feces deposited in small shaded areas. The first signs of foot rot, following an incubation period of five to seven days, are lameness, acute swelling of interdigital tissues, and swelling evenly distributed around the hairline of both hooves. Eventually the interdigital skin cracks open, revealing a foul-smelling, necrotic, core-like material. Untreated, the swelling may progress up the foot to the fetlock or higher. More importantly, the swelling may invade the deeper structures of the foot such as bone material, joints and tendons.
Diagnosis and Other Related Conditions
Diagnosis of foot rot can be made by a thorough examination of the foot, looking at the characteristic signs of sudden onset of lameness (usually one foot), elevated body temperature, interdigital swelling, and separation of the interdigital skin. Other conditions causing lameness and affecting the foot that may be confused with foot rot include:
Additionally, cattle grazing endophyte infected fescue pastures that develop fescue toxicity, causing loss of blood circulation to the feet and subsequent lameness, are sometimes mistaken as having foot rot.
Treatment of foot rot is usually successful, especially when caught early in the disease course. Treatment should always begin with cleaning and examining the foot to establish that lameness is actually due to foot rot. At this time, a topical treatment of your choice should be applied. Some very mild cases will respond to topical therapy only. Most cases require the use of systemic antimicrobial therapy. LA 200®, Bio-Mycin 200®, Procaine penicillin G, Tylan 200®, and Sustain III™ (sustained release Sulfamethazine) boluses are over the counter pharmaceuticals that have proven effective as a treatment of foot rot. Naxcel®, Micotil®, and Albon S.R.® (sustained release Sulfadimethoxine) boluses are antimicrobials restricted to the use by the order of a licensed veterinarian, and have also shown to be effective in the treatment of foot rot. Your veterinarian may deem it necessary to use or oversee the use of one of these restricted drugs as a treatment for non-responding cases.
If at all possible, affected animals should be kept in dry areas until healed. If improvement is not observed within three to four days, it may mean the infection has invaded the deeper tissues.
Preventive measures are centered on the prevention of mechanical damage to the foot. This is common from running cattle on frozen or dried mud, shredded weeds or brush, and stubble minimizing the time cattle must spend standing in wet areas. Other preventive measures presently used include the use of footbaths (most often used in confinement beef or dairy operations), feeding low levels of chlortetracycline, addition of organic and inorganic zinc (especially Zinc methionine, ZinPro®) to the feed or mineral mixes, addition of iodine from EDDI and vaccination.
When cattle are moderately to severely deficient in dietary zinc, supplemental zinc may reduce the incidence of foot rot. Zinc is important in maintaining skin and hoof integrity; therefore, adequate dietary zinc should be provided to help minimize foot rot and other types of lameness. In a three-year study, zinc methionine added to a free-choice mineral supplement reduced the incidence of foot rot and improved daily weight gain in steers grazing early summer pasture.
Foot rot is one of many conditions of the foot that cause lameness in cattle. It helps to have a better understanding of the condition in order to identify and treat it properly. Check with your local veterinarian for additional information as well as other, effective treatment methods.
Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, TX. He can be reached at P. O. Box 653, Sulphur Springs, TX 75483, by phone at (903) 885-7992 or by e-mail at email@example.com.