28 February 1997

WINTER PEAK FOR LAMENESS OF THE WORST VARIETY

Lameness caused by digital dermatitis needs careful treatment to keep it under control. Cheshire vet

John Dawson explains

WINTER brings no surprises when it comes to lameness. And digital dermatitis, both painful and infectious, has certainly caused explosive outbreaks of very lame cows within herds this year.

First diagnosed in Britain in 1986, it has spread at a great rate and can now be seen in over 60% of herds, sometimes affecting up to 60% of cows.

Incidence increases dramatically during the winter as the wet, unhygienic conditions underfoot allow rapid spread and penetration of the disease-causing organism. It also causes lameness during the grazing months, but the spread is less rapid as stocking density is less, and conditions underfoot dryer and more hygienic – cows feet are only exposed to slurry twice daily at milking.

Treatment takes several forms, with the method of application tailored to the individual farm facilities and abilities. Topically applied antibiotic solution is the only effective treatment. Some resistance has been eluded to against the most effective antibiotic, Lincomycin. In my experience, if adequate Lincomycin solution is used, then the suggested resistance problem is reduced or absent. However, if there is a serious problem of resistance other antibiotics have been effective.

Antibiotic treatment

Individual cases are treated, after trimming, with antibiotic. Apply with a hand-held sprayer to the exposed washed area of infection. One application of the antibiotic cures most cases, but respraying until cows walk soundly is advisable, especially when large areas of skin are infected. Neglected cases with coronary band/corium involvement require multi-dosing daily, preferably stand the foot in the solution during milking to allow good penetration. Penetration of the antibiotic is difficult due to the thick layer of necrotic tissue; trimming, thorough cleaning and removal of necrotic tissue is advised. Dosing daily for up to 10 days will cure most deep rooted, neglected infections.

Whole herd treatment in the face of an outbreak should be applied via a knapsack sprayer or foot bath. In both cases the feet must be clean. This is best achieved by power washing the feet in the parlour after the cows are milked. The Lincomycin solution is sprayed onto the feet as the cows stand in the parlour with the knapsack sprayer, or through the foot bath as they leave the parlour. Cows are treated at six consecutive milkings and the solution in the foot bath needs renewing if it become excessively contaminated. Cows should then stand on a clean scraped yard for 20min to allow good penetration of the antibiotic before returning to the cubicles.

Reduced resistance

Adequate dosing and antibiotic concentration reduce the chances of resistance and give a good response to treatment. Application onto a clean infected area, and allowing the cow to stand after application in a clean, dry area to allow penetration of the antibiotic will help to produce a more effective cure and reduce the chance of resistance. Early treatment gives the best cure.

Routine trimming all cows in the herd is a good policy for general lameness control as well as digital dermatitis. Incidence can be reduced during housing by scraping passages at least twice daily, providing ample loafing area and using plenty of bedding in the cubicles.

Keeping their feet as clean as possible is the key. Heifers introduced into the herd are most susceptible, and treating lame heifers as soon as lameness signs arise minimises problems. Antibiotic solution should only be used when cases of digital dermatitis have been diagnosed. Change the type of antibiotic used only when true problems of resistance have been established as it encourages multi-resistant bugs. Correct use of correct strength solutions reduces resistance problems. &#42

An example of a typical, early non-complicated case of digital dermatitis.

Cheshire vet John Dawson.

Neglected cases require multi-dosing daily. In this example infection invaded the corium destroying the hoof attachment. The hoof shell came off easily.


Digital dermatitis is an extremely painful disease of the dermis (skin). Lesions have a strawberry appearance commonly seen on the heel. All other regions of skin, from horn to fetlock can be infected including inter-digital growths. A typical infection covers a small area of heel the size of a 10p coin when diagnosed early. If the coronary band – the living layer of the hoof which corresponds to the quick of the finger – becomes infected horn growth can be stopped irreversibly. It becomes very difficult to treat requiring radical trimming of all the under-run and infected horn. Neglected infections are sometimes impossible to treat.


CONTROL


&#8226 Routine foot trimming.

&#8226 Scraping twice daily.

&#8226 Use plenty of bedding.

&#8226 Key is clean feet.