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Preventing Winter Lice and Ringworm

February 20, 2020

Preventing Winter Lice and Ringworm
By Will Winter, DVM

A lot of ranchers seem to think that skin parasites such as winter lice or mites (that cause mange) are “nothing” issues. Minor irritants, not much more. The reality is that in addition to being a humane issue, these parasites cause stress, weight loss, reduced milk flow, anemia and more. Ringworm is another common problem that many ranchers ignore. Primarily because once the sunshine and green plants return, it tends to go away. Ringworm is a fungal infection of the skin, an organism that is closely related to athlete’s foot in the human. The highly contagious fungus damages the hair and skin causing unsightly dry, scaly bald patches. This causes the animals to lose even more body heat in the winter, causing them to scratch and go slightly off-feed and give the herd the appearance of being “poor doers”.

Remember that all illnesses can be tracked back to a nutritional deficiency! In the case of parasites, it’s almost always a vitamin or mineral deficiency, but it’s also essential that all caloric (energy), protein, and other macro-nutrient needs be met. Suffice it to say that it’s critical to offer a full-spectrum mineral mix, ideally free-choice, year-round. Fat soluble vitamins such as A, D3 and E are naturally deficient in the darker times of the year, especially considering most forages are dormant or stored feed. Maintain the vitamins year-round, but if you commonly see winter lice or ringworm, it’s a guarantee that your herd is vitamin-mineral deficient.


Genetics play a huge role in parasite resistance. When cattle are bred carefully, paying attention to not only production numbers but also for that overall sheen in the haircoat, the bright eye, and the exuberance for full life, there will rarely be parasite problems. We can also use the degree of parasite load as an excellent culling tool. Remember that the cardinal rule of all parasites is that they are here to do something very essential to the big picture: that task of removing the weak genetics. Those animals that attract parasites are sending out (measurable) electric signals that attract the parasites! “Come eat me”, they are saying.

Lastly, how you graze your animals is of paramount importance to parasite prevention as well. You must prevent against grazing your forage too short, even in the winter when its dormant, because parasites can only make it up about 2" high on a plant. So, if you can keep your animals grazing forages that are higher than 2" off the ground then you are helping them from getting those parasite loads. Sunlight is also important, so don’t keep your animals in a barn consistently, even if it’s cold. Feed your stored forages out in the pasture or stockpile forage so you can keep them grazing outside in the winter.

Prevention of winter lice and ringworm is your best bet for saving time, money and anguish, but prevention isn’t always possible. So next time we will discuss some natural treatment options.

Matt Buhmann

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