Healthy Cows from the Hoof Up
by Carrie Bargren, DVM
When a cow develops a foot disease, as with most health problems we work with, there is usually an underlying cause. With foot disease, the source of the problem can vary greatly, from the surface she walks on, to how long she stands waiting to be milked, to what the temperature is that day. Just treating a lame cow can be as simple as a trim, a medicated wrap or a foot block. But finding the cause can be quite frustrating, especially when multiple components are involved. Fortunately, the lesion itself often provides the answer.
The cost of a lame cow can be significant over time. She will lose about three pounds of milk per day, with the biggest losses due to foot rot and sole ulcers. There will be a delay in her return to a normal heat cycle post-calving, and she can take up to 50 extra days to conceive. In addition to the extra cost of a therapeutic foot trim and treatment, there is a 2 to 4 times higher risk of her being culled than a non-lame cow.
Regular hoof trimming is essential for foot health. A proper trim re-establishes the weight distribution between claws and an upright foot angle. It also allows for routine screening and treatment of foot lesions before they become more serious. If done incorrectly, trimming can cause additional problems, often due to excessive trimming. A cow should never be more lame after being trimmed. Fortunately, over-trimming is easily remedied once noticed and isn’t common.
The benefits of a good trim last about four months, as the hoof grows about 0.5cm per month. All cows should be trimmed at dry off and will benefit from an extra trim around 80-150 DIM. Heifers with overgrown claws should be trimmed right before calving.
In addition to a good trim, training yourself or your herdsmen to locomotion-score the cows will provide information on the prevalence of lameness in your herd. Accurate record keeping of the lesions that were treated will identify the most common ones, and the cause can be addressed.
The most common foot lesions can be divided into two categories: claw horn lesions and infectious lesions. While they can and should be treated, prevention is the key, and each type has a specific cause that can be addressed to improve overall foot health.
Claw horn lesions include those on the walking surface of the claw. Prevalence of these lesions increases with every lactation. Ulcers on the sole, heel and toe form when connective tissue in the foot weakens around calving time due to a combination of hormonal changes from calving and a subacute ruminal acidosis. The weakened connective tissue results in an increase in pressure at a focal point on the bottom of the foot, creating a painful lesion. Older, thinning cows will lose fat from a fatty cushion on the bottom of the claw, further increasing pressure on the bottom of the foot.
To reduce ulcers, focus must be placed on cow comfort, including time budgets, stall comfort and heat stress. The time budget is a breakdown of what a cow does with her day and includes time out of the pen for milking, time up feeding, time in the alley, time standing in the stall and time lying down. An increased time out of the pen and therefore standing is associated with increased lameness, and can be caused by any of the factors within the time budget such as poor stall comfort, prolonged milking time or prolonged lock-up time. Cows bedded in sand are known to be less lame, in both free-stalls and tie-stalls. A lame cow will resist the action of lying down and rising which disturbs her normal resting behavior. On sand, the cow rises easier and there is more cushion for a sore foot and a resting body, both of which will increase lying time. Incorrect heat abatement not only leads to poor milk production alone, but a cow cools herself by panting which she can only do standing, leading to prolonged standing times — which are hard on her feet.
Another common claw horn lesion is white line disease, which describes lesions on the bottom of the foot where the horn meets the sole. Lesions are typically ⅔ back from the toe and include hemorrhage, fissure, and abscess, all of which are caused by external forces. With a high level of white line disease, focus on improving walking surfaces. Trauma to the foot is caused by the cow walking long distances to the parlor, rough walking surfaces, excessive grooves or slatted floors. Smooth, slippery floors, especially at crossovers and turns where high traffic has worn down the grooves, are hard on the foot. Wear on the foot and bruising occur with walking long distances and concrete floors. A simple solution is to strategically place rubber mats in key areas such as transfer lanes, holding areas and even in the parlor to provide extra cushion and traction. Be careful about installing mats in the pens however; if the rubber mat is more comfortable than the stall, the cows wills choose to lie in the alleys.
For all claw horn lesions, a correctly formulated and fed ration as well as proper feed access will reduce the likelihood of a cow getting subacute ruminal acidosis that aids in the weakening of connective tissue in the foot.
The most common infectious foot lesions are heel warts and foot rot. Heel warts (digital dermatitis) are caused by multiple pathogens including Treponemes and many bacteria. They are a disease of modern free-stalls, since they are caused by a combination of damage to the foot from being continuously wet from manure in the alleys and a low oxygen environment on the foot from being covered in manure. Treponemes prefer a low oxygen environment, and the foot is trimmed to expose the Treponemes to oxygen as well as a topical antibiotic for the other bacteria. Having comfortable stalls will encourage cows to spend more time in the stall where their feet can dry rather than in the wet alleyways.
Foot rot, or interditigal phegmon, is an extremely painful inflammation of the skin and tissue in the space between the claws. It’s most commonly caused by Fusobacterium necrophorum, which excretes an endotoxin that kills inflammatory cells and bursts red blood cells, causing the tissue to disintegrate and fall off. Other than lameness, the only other sign might be a slight swelling on top of the foot at the edge of the space between the claws.
In order to control infectious lesions, place your focus on good hoof hygiene and footbaths. Trimming and topical/injectable treatment are necessary to treat active infections. Footbaths prevent chronic heel wart lesions from becoming active and prevent active infections from becoming smoldering chronic lesions that serve as a reservoir for the disease. The footbath should be 10-13’ long, which allows for 2-3 immersions per hind foot in the chemical. To keep volume low, it can be narrow (20-24”), and a 10” step prevents spillage without affecting the cow. In addition, installing solid side-walls keep the cows moving forward. The most common chemicals used are copper sulfate and formalin, of which copper sulfate has slightly better efficacy. An old bulk tank can be repurposed to safely pre-mix the chemicals and pump them to the footbath. There is no set interval for using a footbath, other than to bathe as often as necessary so less than 5% of feet at dry off have any infectious lesions. Anywhere from once weekly to three time a week is common.
There can be so many factors contributing to foot disease that it can be quite frustrating. If your herd’s foot health could improve, let us know and we will gladly work with you to investigate, find the source and determine the best course of action.