THE MERCK VETERINARY MANUAL
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Preventive Procedures in Cattle Lameness

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Surgery, injury to tissues, and swellings caused by infection result in pain. The stress response to pain increases the nutritional requirement of the animal (particularly zinc intake) and, if prolonged, can cause debility. Pain-related stress may also increase susceptibility to disease. Measures to control pain (eg, use of analgesics) promote healing and recovery. Analgesic drugs should be administered to effect, but the following dosages can be used as guidelines: morphine, 0.2–0.4 mg/kg, IM; meperidine, 1–2 mg/kg, IM; oxymorphone, 0.05–0.1 mg/kg, IM; pentazocine, 1–2 mg/kg, IM; butorphanol, 0.1–0.2 mg/kg, IM or IV; and buprenorphine, 0.005–0.008 mg/kg, IM or IV.

The use of corticosteroids and NSAID is controversial, but the latter are useful in counteracting substances such as prostaglandins from injured and inflamed tissues. NSAID are valuable for treating pain due to inflammatory reactions or joint diseases, but their use for long periods should be avoided because of adverse side effects. For example, phenylbutazone should not be administered more often than once every 36–48 hr and not repeated more than 2–3 times. The following NSAID are commonly used: aspirin, 100 mg/kg, PO, bid; flunixin meglumine, 1.1–2.2 mg/kg, IV or IM; phenylbutazone, 10 mg/kg, IV or PO, every 48 hr; and dipyrone, 20 mg/kg, IV, IM, or SC, bid-tid. Dimethyl sulfoxide is a topical anti-inflammatory agent that can be applied over the affected area.

Over time, the claws of cows wear, changing the shape of the sole, which in turn makes the foot unstable. The two claws become unbalanced both longitudinally and laterally. As changes occur in the lateral claw, it becomes “overloaded,” the heel horn may become thicker (overburdened), and posture is compromised. The objective of trimming, therefore, is to restore the normal equal distribution of weight-bearing in the foot.

Under normal circumstances, horn growth keeps pace with wear. The growth/wear rate at the heel is greater than it is at the toe. Horn that is dry tends to be extremely resistant to wear and may grow longer than normal. Thus, the claws of cattle maintained in straw yards tend to become overgrown. Conversely, the claws of cattle maintained in extremely wet conditions are softer than normal and more prone to wear and damage. If the animals are housed on concrete surfaces, the lateral hind claw tends to wear less than the medial.

It has been reported that if claws are correctly trimmed at least once each year, longevity of the herd may be extended by 1 yr. However, trimming will result in a decrease in the milk yield by up to 2 lb/day for 2 days, which is partly due to disruption in the cow's feeding routine and handling. Trimming should be avoided in any location close to the milking parlor and individuals handling the cows should never attempt trimming. Unskilled claw trimming should be avoided, as it has a negative effect on the claw health of a herd. In many countries, claw trimming is performed by professional claw trimmers rather than veterinarians. Claw trimmers usually keep extensive records of the lesions present in all claws, which can be invaluable information for the veterinarian who is increasingly required to investigate lameness as a herd problem.

All claws should be evaluated before trimming. On average, the front (dorsal surface) wall of a hindclaw measures ∼7.5 cm long from apex to hair line. When the dorsal wall increases in length, the dorsal surface of the claw tends to become concave (buckles like the instep of a human shoe). This causes greater weight-bearing to be transferred to the posterior aspect of the claw, increasing pressure on the flexor process of the distal phalanx, the point beneath which sole ulcers develop. The longer the toe, the greater the stress on the flexor system. In all cases, the angle between the dorsal wall and the ground surface should be ∼45° at the toe. When the claws are short and the dorsal wall is >7.5 cm, there is a considerable risk that the thickness of the sole at the apex will be less than the desirable 7 mm. Thinning of the apex of the sole of short-clawed animals should be avoided.

The Dutch method of claw trimming consists of 5 steps. In every case of lameness in which there is a lesion in the sole, the first 3 steps must be performed before attention is turned to the lesion itself.

In step 1, the length of the dorsal wall of the medial claw should be cut back to 7.5 cm. The thickness of the sole at the apex should be ∼5–7 mm. The horn beneath the bulbs should not be trimmed at this stage.

In step 2, both the sole and the heel of the lateral claw should be shortened to match the medial claw. This may not be possible if the medial claw is already <7.5 cm long. When the heel of the lateral claw is significantly thicker than that of the medial claw, excess horn should be removed to establish lateral stability. If slight resilience in the sole is detectable on thumb pressure, no more horn should be removed. The claw should be left flat from apex to bulb. Lack of attention to these principles may result in too much sole being left in the center of the prebulbar region, in which case sole ulcers can develop. A common error is to reduce the bearing surface of the wall at the level of the axial groove—a procedure that may transfer weight-bearing to the center of the sole.

In step 3, the central quadrant to the axial border of the sole is shaped to a gentle slope from the abaxial to the axial border.

In step 4, because >90% of lesions causing lameness are found in the sole of the lateral hindclaw, the strategy is to transfer weight to the medial claw by leaving it untouched while the thickness of the sole of the lateral claw is reduced as much as is reasonable in the prebulbar and bulbar regions.

In step 5, rough fragments of sole horn should be removed. If cows with problem claws are encountered during the annual herd trimming, the claws should be trimmed twice each year thereafter. It is preferable for claw trimming to be done when cows are not heavily pregnant, nor should it be done during peak lactation.

The use of a footbath is not a substitute for either good hygiene or claw trimming. Permanent, concrete foot baths may measure 10 ft in length and be at least 3 ft wide. Drainage must be provided to ensure that it may be properly cleansed. The sides of the bath should slope inward to a maximum depth of 6 in. Ideally, 2 baths should be built in sequence. The first bath would contain a foot-washing solution, the second would be medicated. Portable baths constructed from fiberglass are available. A hoof mat, consisting of a sheet of foam plastic encased in a perforated plastic cover, is also available. The foam is soaked in medication that squirts up between the claws when the cow walks on the mat.

Formalin (3–5%) is the least expensive footbath solution for the control of footrot. It has been found of value by some veterinarians when used alternately with antibiotics in the control of digital dermatitis. The solution should be changed after the passage of ∼250 cows, more frequently if the bath is heavily contaminated with manure. Formalin has good bacteriostatic activity and some potential for hardening the epidermis. However, it is ineffective at temperatures <13°C. Formalin is regarded as a hazardous waste, and in many districts land disposal restrictions may be in force and should be followed. Formalin generates strong fumes that irritate the lungs of milkers and can taint milk. It should never be used in baths located near the milking parlor.

The stronger the formalin solution used, the more effective it is, but the danger of a chemical burn on the cow's skin when she is lying down is also greater. Therefore, the status of the hair around the claw should be carefully monitored. If the hair appears to be standing on end or the skin is pink, treatment should be suspended. Normally, cows can tolerate twice daily baths for 3 days using a 3% solution. The treatment should be repeated every 3 wk. Higher concentrations should be used for the most resistant conditions.

Footbathing with a 5% solution of copper or zinc sulfate controls interdigital dermatitis and is of some value in controlling footrot (interdigital phlegmon). The sulfates are quite rapidly deactivated by combining with the proteins in manure. Prewashing of the cow's feet is advised, and the solution should be changed after the passage of 200 cows. Copper sulfate, although not universally regarded as a hazardous substance, is toxic to fish so it must not be released into waterways. There is some evidence that copper tends to make essential trace elements less available to cattle. For this reason, it is unwise to allow waste copper sulfate to enter the ground water. Local authorities should be consulted before this chemical is allowed to enter a sewage system.

The use of antibiotics in footbaths has been a popular strategy for the treatment, control, and prevention of digital dermatitis. The cost can be reduced by using a “minimal fluid footbath.” The type of antibiotic used in footbaths should be changed at intervals of ∼6 mo to avoid development of resistant strains of the causal organisms. However, treatment may be given for 2 or 3 days and repeated once after 7 days. Formalin footbaths may be used alternately if more aggressive treatment is necessary. Antibiotics used in footbaths do not result in detectable levels of the drug in the bloodstream.

A new generation of chemical agents has been developed for use in footbaths. Claims for the effectiveness of these and other products have not yet been adequately substantiated in controlled trials. Foams are also available but require considerable cost for associated equipment. A foam keeps the chemical agent in contact with lesions better than does a liquid product.

Last full review/revision March 2012 by Paul R. Greenough, FRCVS

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