Scratching the Surface: Investigating the Prevalence, Nature and Potential Causes of Itchy Cattle

Background

Producers and veterinarians have reported cattle losing hair even after being treated with a pour-on “mectin” product (e.g., Ivomec). This is often assumed to mean lice are developing resistance to these products. However, some vets who have investigated these cases report that they haven’t necessarily found lice. Besides biting and sucking lice, other potential causes of itching include other parasites (e.g., microscopic mites), environmental factors (e.g., barley hull allergy, frost bite, straw mites), nutrition (e.g., Vitamin A or zinc deficiencies) and mycotoxins (e.g., ergot, citrinin, T2 toxins). This research team wanted to see if they could find the cause of and solutions to the itchy cattle problem.

Objective

• To provide insight into the cause and potential prevention/treatment of itching beef cattle in Western Canada

What they did

The team worked with seven herds that had more than 30% itchy cattle in Alberta, Saskatchewan and Manitoba. They examined and documented the baldness patterns, treatment history and nutritional management. They also tested skin for pathogens (e.g., lice, mites) and skin hydration and allergies. Additionally, they collected feed and blood samples for nutritional deficiencies.

Blood samples were collected from 10 itchy and five non-itchy animals in each herd and were analyzed for a variety of metabolites and nutrients to assess mineral and vitamin status of the animals (for a total of 101 cattle). A subset of animals also had liver biopsies done to further assess mineral status. Baldness patterns were photographed, and itchiness and skin injuries/traumas were scored. Biting and sucking lice were collected and counted at three locations on each animal, and the louse species and level of infestation were determined. Cattle were skin tested for hypersensitivity to five different antigens and irritants. Skin scrapings were collected from the edges of lesions to look for chorioptic and sarcoptic mange mites. Skin samples were collected for histopathology and analyzed for signs of disease.

Forage and grain samples were collected and analyzed for nutritional composition, including antagonists that might make certain minerals unavailable to the animals and potentially cause secondary nutritional deficiencies. Water samples were also analyzed for factors that might tie up mineral absorption. Liver and kidney panels were done to rule out ergot and mycotoxins in the feed. Bedding and hay were tested for straw mites. The data were analyzed to identify factors that may play a role in the itchy cattle syndrome.

What they learned

All 101 cattle enrolled in the study were in adequate body condition (BCS 3 to 4 using the Canadian 5-point system). Only a single species of lice (sucking louse), which causes minimal irritation, was identified and present in very low numbers in 21 out of 101 cattle. Itching was unrelated to the presence of lice. Skin mites were not observed from the skin scrapings, hair or skin biopsies taken from any animals, ruling out mange as a cause of hair loss. The presence of skin hypersensitivity or allergic reactions to the five allergens (i.e., grass, weeds, mold, grain and alfalfa) was very low across itchy and non-itchy cattle and did not differ between the two groups, within herds or among different herds. Skin hydration measurements showed only one herd demonstrating significantly drier skin in locations with hair loss compared to normal locations that had hair. Vitamin A, E, copper, cobalt, zinc and molybdenum blood analyses showed no significant difference between itchy and non-itchy cattle; however, selenium levels were significantly lower in itchy cattle as compared to non-itchy cattle across the seven farms, but marginally above the level that is considered deficient. However, liver copper levels were lower in itchy versus non-itchy cattle. All herds that were offered free-choice minerals and vitamins had copper-deficient cattle. Liver and kidney panels were all negative indicating that mycotoxins or ergot did not cause itchiness and hair loss. Water samples all exceeded the acceptable sulphate levels which may have interfered with copper absorption.

what it means

These results suggest that the itchiness in cattle is complex—it is not simply a result of lice infestations. There may be multiple factors involved, and mineral deficiencies may play a role.

Producers who observe itchy cattle should start by inspecting them for lice. If no lice are found, work with your veterinarian and nutritional consultant to examine herd health and feeding management practices that may be involved. Mineral and vitamin supplementation programs deserve careful consideration, especially when these supplements are offered free choice.

The research team is planning further studies to see whether copper supplementation can resolve itchiness.