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A certain amount of scratching in cattle is natural

Animal Health: Most delousing products will do the job, but there are exceptions

With the advent of the reliable pour-on and injectable endectocides, scratching from lice or mange is rare unless a fall treatment was not done or we have biting lice or mange about.

Veterinarians are sometimes called on to investigate apparent breaks in these products’ efficacies. I know we have observed a lot about cattle’s scratching behaviour which we never knew before, since lice or mange were always blamed in the past.

A visual examination or discussion over the fence is not enough when there is hair loss. We examine several affected animals and usually clip hair surrounding the worst-affected areas. If pests are present, careful visualization by the naked eye or with a magnifying glass can detect some external parasites. Deeper skin scrapings can be done as well because we don’t want to miss mange mites if they are present.

Product failures are rare but if they do occur, usually either biting lice or chorioptic mange are the culprits. These external parasites may survive because both are surface feeders and move around a lot, so control may not be quite 100 per cent. Also transmission of the pests is quicker so new introductions can spread easily. A common question is when and how long ago new introductions happened and whether they had been previously treated. This, together with proper dosage and administration based on accurate bodyweights, is extremely important.

Guns for applying endectocides now disperse the product more accurately over the back. Newer products such as Saber, Boss or Cy-lence as well as products for cattle oilers such as Ectiban have been developed specifically for lice. With all products stick to the dosage recommended.

Some also have indications for ticks which we are seeing more of on cattle across Western Canada. For instance, in B.C. ranchers may spray the cattle with the Ectiban (permethroid-permethrin) product under the advice of their veterinarian. As with all the external parasites that move or intermittently feed, the best results are achieved if the insecticide has contact with the insect.

Don’t overtreat

For most products, repeat treatment is recommended in two to three weeks if necessary. If you need to treat more frequently, the problem may not be external parasites. Also, too many treatments too close together could be detrimental to reproductive performance of young bulls’ semen quality. Again, stick with the recommended dosage and method of administration. Regular dosage of the permethrins has been proven to be non-detrimental to semen quality and testicular development.

Other causes of scratching vary in herds. If severe enough, ringworm, which is commonly seen around the eyes and head, will cause irritation and scratching, especially in young cattle. Look closely for circular lesions in other locations. One treatment for ringworm will usually get them on the road to recovery.

Bale processors and other grinders do a great job chopping and dispersing feed, but also deposit a lot of dust and/or debris in the hair. With sweating in warmer weather, this scurf and debris can cause intense itchiness in certain locations. Once cattle start rubbing, soreness and bleeding occur, adding to the problem. A lot of these itching episodes will often follow unseasonably warm periods in the winter after cattle have haired up. Free-living mites in grain or on bedding also cause cattle to itch. Some producers will lock cattle out when bedding or provide oilers or rubbing brushes to help to remove the fine dust debris and straw.

Certain individual or genetic strains of cattle may be allergic to certain feeds or moulds present. Allergic reactions will vary in severity but many will cause reddening of the skin and swelling associated with itchiness. Here the allergen must be removed before recovery can happen.

Nutritionally the skin must be healthy otherwise itching, as a result of deficiencies may be a possibility. Trace minerals should always be fed as part of the overall nutritional package. Important ones for skin health are zinc, copper and vitamins, especially vitamin A. Unhealthy skin also allows various bacteria to take hold. These infections can be intensely itchy and spread locally.

If washed, show cattle must be thoroughly rinsed, otherwise the residual soaps can cause irritation or allergic reactions.

Some rubbing and licking is part of cattle’s natural grooming process. We should only be concerned and investigate if there is excess skin damage or hair loss.

Regardless of the cause, constant irritation can result in weight loss and a predisposition to other diseases. Cattle will eat less and anemia can result from the blood loss, especially if sucking lice are involved. Hair loss removes cattle’s insulative coat. This is stressful in deep-freeze weather, requiring more energy to keep warm.

Most parasitic causes of scratching will be minimized by routinely using a specific lice treatment. If scratching continues, have the problem fully diagnosed so preventative measures can be taken to eliminate the problem. This may involve close examination, a skin scraping, or even a skin biopsy. Health of your cattle is reflected in healthy skin and a shiny hair coat.

About the author

Columnist

Roy Lewis is an Alberta-based veterinarian specializing in large-animal practice. He is also a part-time technical services vet for Merck Animal Health.

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