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Horn Growth-How and Where It Occurs S .R. van Amstel BVSc, Dip Med Vet, MMed Bet (Med) Department of Large Animal Clinical Sciences College of Veterinary Medicine, University of Florida
J. K. Shearer DVM. MS Department of Large Animal Clinical Sciences College of Veterinary Medicine, University of Florida
Claw trimming is unique in the sense that it is an art based on scientific principles. The art of claw trimming is the skillful manipulation of trimming tools, particularly the hoof knife, re-establishing size, shape and function. The scientific basis of claw trimming is contained within the concept of functional weight bearing. Functional weight bearing is even distribution of weight bearing forces within the claw and equal weight bearing between claws. Even distribution of weight bearing forces within a claw is largely based on claw dimensions. One of the most important dimensions to consider is the dorsal wall length or toe length. A dorsal wall length of three inches will correlate with a sole thickness at the toe of 1/4 inch. This will result in a normal toe angle of 45-50 degrees. If the heel is also of normal height, the weight bearing axis will be centered through the middle of the third phalanx.............. This article is available in its entirety from
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Foot Trimming: Why, When And How an excerpt from: Sole Ulcers, White Line Disease, and Infectious Claw disorders: Primary Causes of Lameness in dairy Cattle By Dr. Jan Shearer DVM, MS University of Florida Why? Hoof growth is relatively slow at about 5 mm per month. Shape of the hoof is a product of the rate of growth verses the rate of wear. overgrowth is more or less a natural consequence of feeding and housing conditions common to intensive dairy production. the effect of hoof overgrowth is over loading, particularly of the lateral clawsof rear and the medial claws of front feet. Overgrowth is manifested primarily at the toe. Hoof horn is harder, growth is more rapid, and the rate of wear is less at the toe. In contrast, hoof horn is softer, growth is lower, and the rate of ear (weight-bearing is greater) is more rapid at the heel. The end result is a lengthening and raising of the toe with a corresponding lowering of the heel. The angle of the front wall may be altered from a normal of 45 degree to 30 degree or less. Overgrowth also occurs on the sole. Humans develop calluses on the weight-bearing areas of their feet (balls of the foot and heel). Cows don't develop calluses; instead they produce more horn on the soles of the weight-bearing claws (i.e., lateral claw of rear and medial claw of front feet). The dynamics of hoof growth and over growth are even more exaggerated for cows that have experienced laminitis or for those housed on concrete or other hard flooring surface. The purpose of foot trimming is to re-establish appropriate weight-bearing within and between the claws of all four feet. In so doing, trimming reestablishes proper function. When? Most cows will benefit from trimming 1-2 times per year. There are a few cows which may require hoof trimming more than twice per year. The majority of operations trim cows one time per year at dry-off. Considering the foregoing discussion of the effects of feeding, housing, and laminitis on hoof overgrowth, one could justify trimming (or at least an evaluation to determine the need for trimming) at mid-lactation. It is obviously more risky to trim cows at mid-lactation, however trimming at dry-off only assures that most cows will go well beyond one year before seeing the trimming chute. Depending upon housing conditions and the prevalence of laminitis, problems with hoof over growth and claw disease are near certain for some hers which trim only at dry-off. How? the fundamentals of hoof trimming are well described by Raven in his book, "Cattle Footcare and Claw trimming". Readers are advised to consult this book for a more in-depth review of this topic. For the purposes of this discussion we have chosen to outline the procedure for trimming feet into six basic steps. The objectives of preventative hoof (claw) trimming are:
The following 6-step plan for trimming is recommended: Step 1 Judge the length of the claws. Since the nner hind claw represents the more normal claw, this claw is used as a model for th more abnormal outer claw. the front wall of the medial (inner)claw should be 3 inches long (from the skin-horn junction to the tip of the toe). This length of 3 inches (7.5 cm) is taken as the correct front wall length for the average Holstein-Friesian cow. thickness of the sole should be a minimum of a 1/4 inch. Spare as much of the heel on the medial claw as possible. Reduce the length of the inner claw to this required length. Next the bearing surface (sole and wall but not the heel) is "stabilized" on the inner hind claw. In other words, the bearing surface of the toe and wall is pared flat so that it will be at right angles to the long axis of the shin (cannon) bone in the standing position. This will ensure that the cow has a flat and stable supporting weight-bearing surface on hard ground. the heel of the inner claw is not trimmed down unless overgrown. furthermore, since claw lesions in the outer claw are the more frequent circumstance, preservation of th heel on the inner claw is desired in the event that it is necessary to provide rest to the outer claw by increasing weight-bearing on the inside claw heel. A proper dorsal wall length (at least 3 inches) will ensure adequate sole thickness particularly at the toe where sole thickness of a least a 1/4 of inch (5-7mm) is required. The sole in this area should not "give" under pressure. If it does it may indicate that the sole has been trimmed to thin. Thin soles subject the underlying corium to bruising or a greater potential to wear through, particularly at the white line. Exposure of the corium often leads to grave consequences for the foot. Step 2 Using the nedial claw just trimmed as a guide, trim the toe of the outer claw )rear foot) to the samw lentth. Next, pare the weight-bearing surfgace (of th sole) of the outside claw to the same level as that of the medial claw. The outer claw is trimmed to the samw level as the inner claw both at the toe and at the heel. Again, the bearing surface should be flat and balanced with the outer claw. Leaving a damaged outer claw higher than the inner claw will probably lead to lameness. It is forthis reason that the inner claw heel is preserved. When complete the weight-bearing surfaces should be flat at the toe. Step 3 shape and slope the sole so that the innermost back portion of the sole slopes toward the center of the claws. Care should be taken to avoid paring away important weight-bearing surface at the toe. Excessive cupping or sloping of the sole should be avoided because it reduces the weight-bearing surface area to the outside walls. this is one of the most common errors in foot trimming. Proper sloping of the sole in this region is designed to reduce pressure in the sole-ulcer site area and open the interdigital space between the claws. Overgrowth of the sole which occludes the interdigital space causes dirt and manure to be entrapped between the claws. this increases the likelihood of interdigital disease. Step 4 Balance the heels. Weight-bearing surfaces should be flat at the toes, along the walls, and across the heels . this assures an appropriate distribution of weight within and between the claws and completes the trimming process in feet where furthercorrective trimming procedures are unnecessary. Steps 5 and 6 are characterized as "therapeutic and curative trimming procedures". They are applied as needed. Step 5 Paare the damaged claw lower toward the heel to increase weight-bearing on the healthy claw. In most cases the damaged claw will be the outside claw of rear and the medial claw of front feet. Specific indications for this trimming procedure would include conditions in which overgrowth has led to overloading (i.e. hemorrhage at the sole ulcer site) or excessive weight-bearing on the claw. Lowering the damaged claw reduces weight-bearing and thereby permits recovery and eventual return to normal function and health. In some cases it is necessary to apply a foot block to the healthy claw in order to reduce weight-bearing in the damaged claw. Step 6 In the presence of hoof horn lesions, further corrective trimming is necessary. Remove all loose horn irrespective of how extensive it is (sole separation) and pare away hard ridges (heel horn erosion). only healthy hoof horn should be left in place. Never dig holes. Always slope horn towards the lesion. for example, trim the area around sole ulcers and remove the lateral wall when trimming out white li9ne lesions. trim carefully and DO NOT remove new healthy horn. Avoid damage to the corium (i.e. stop when trimming leads to bleeding of the corium). Do not trim horn with cracks or hemorrhage of the sole excessively; unless there is pain or swelling. Once necessary horn removal has been accomplished, avoid cutting away more horn at each examination unless conditions (i.e. loose or damaged horn) warrant such measures. Part of fixing a foot is trimming a foot. In other words, unless the defect that created the problem is corrected the benefits from curative procedures are short-lived. The step-wise procedure as outlined above, if followed, forces one to observe and trim the healthy as well as the lame foot in a lame cow. Quite often, similar problems can be found in the other foot. Cows that do not respond or get worse within a couple of days should be re-examined. It is the opinion of these authors that every dairy should have (at the very least) facilities for performing foot care and trimming procedures. Large herds (300 hundred cows or more) should consider training personnel on the farm to fix and trim feet on a regular or daily basis. this will assure timely care of lameness and prevent loss of cows from irreversible foot disease.
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