Insect Defense in Horses: Buildings are Preferred as Weather Protection

Weather protection is a must with free-range farming, but is it enough in summer if it is natural?

In two studies, a research group from Aarhus University in Tjele (Denmark) investigated the use of shelters by horses in connection with the insect-repelling behavior of the animals on the one hand and the weather conditions and the resulting insect population on the other.

Course structure

In the first study, the behavior of 39 horses that were kept exclusively on pasture at that time was examined once a week for eight weeks from June to August. 21 horses (five groups) had access to buildings, and 18 horses (four groups) had no access to buildings. The buildings were barns or small buildings with one or more entrances. Natural weather protection was available for all groups. Among other things, the location of the horses (inside the building, in the natural shelter, on the pasture, near the water), insect repellent behavior, and insect prevalence. To determine stress levels, fecal samples were collected 24 hours after data collection to determine cortisol metabolites.

In the second study, 24-hour shelter use using infrared wildlife cameras was analyzed by 42 horses during the summer months. Divided into ten groups, different types of artificial weather protection were available to the horses.

In both studies, weather conditions such as maximum daily temperature, several hours of sunshine, average wind speed, and humidity were documented daily over this period. Horseflies, mosquitoes, and midges in particular were caught using various insect traps and counted every 24 hours.


Based on the weather data and the quantitative evaluation of the insect traps, a correlation of increased insect numbers (horseflies were the dominant insect population) with high daily average temperatures and low wind speeds emerged.

The first study focused on the behavior of the horses and their localization in the housing area. In addition to insect-repellent reactions such as flicking the tail, local skin twitching, head, and leg movements, social behavior, and eating habits were recorded. In all groups, insect-repellent behaviors increased with the number of horseflies counted daily. However, the horses in the comparison group showed this behavior more frequently and intensely. Horses that had access to buildings used them more on days with high insect capture rates (69% of horses) than on days with low insect capture rates (14% of horses). In comparison, the horses stood increasingly close together (less than 1 m apart) without the possibility of standing to benefit from the defensive movements of the others. Fecal cortisol metabolites showed no difference between insect-rich and insect-poor days. In a follow-up study (n = 13 horses, 6 with access to the building, 7 without), cortisol was measured in the saliva on four observation days. Higher cortisol levels could be measured in horses without indoor access on days with high insect prevalence.

The second study shows that the buildings were visited more often during the day and on warm days, although sufficient vegetative weather protection was available on the pasture. At night, on the other hand, building use did not differ over the entire period.

Shadow alone is not enough

In connection with seeking artificial weather protection, both studies do not take into account tolerability in the group or the type and size of the protected area. Small areas, few escape opportunities, and blocking of the entrances by higher-ranking animals hurt the use of the shelter. Nevertheless, it could be shown that the horses visit a building more frequently when there is a high incidence of insects on warm days. They did this even though there was no significant difference in temperature between the building and the pasture and sufficient natural shade was available. Blood-sucking insects are initially attracted by olfactory stimuli and, when approaching, by visual stimuli. An optical blurring of the horses inside the buildings could be an explanation for their difficulty in finding them.

Frequently Asked Question

What to feed horses against flies?

Garlic as a home remedy for fly repellent in horses:

Feed additives can be used to ward off flies in horses with home remedies. Mix around 30-50g of garlic granules or 1 fresh clove of garlic into your horse’s feed.

Why do flies attack horses?

An infestation of horseflies and flies is caused by the natural living conditions of the horses. Horseflies and flies live on the horse’s excrement, blood, and wound secretions. Mosquitoes and flies reproduce particularly well in warm temperatures and humid areas.

What to do against flies in horses?

You boil black tea (5 tablespoons of black tea in 500 ml of water) and let it steep. To do this, mix 500 ml of apple cider vinegar. Put it in a spray bottle and then you can spray your horse before going out for a ride or going out to pasture. This drives away the smell that flies and insects like so much.

What helps against flies in animals?

Freshly planted in pots, herbs such as basil, lavender, peppermint, or bay leaf can have a repellent effect on flies. A so-called “repellent” can help on the pasture, and is sprayed directly onto the animals. To do this, essential oils are diluted with alcohol.

What to do against black flies horse?

Eczema blankets impregnated with pyrethroids are also available to protect horses from insects. Pyrethroids are synthetic insecticides that repel insects. If the horse is allergic to black flies, a change in posture can also provide relief.

How long does black seed feed horse?

Added oils should not be included, but pure black cumin oil. You can also mix in or offer the seeds to your horse if the oil is too gooey and oily for you. You should feed the oil for at least 3-6 months.

What does linseed oil do for horses?

The omega-3 fatty acids in linseed oil have an anti-inflammatory effect and can have a positive effect on immunological processes. The anti-inflammatory omega-3 fatty acids not only affect the joint metabolism but also the respiratory tract and the skin (especially in the case of eczema).

Is tea tree oil toxic to horses?

Tea tree oil has a high allergy potential (and the sweet itch is already an allergy sufferer) and also irritates the skin more than most people realize. Horses in particular are very sensitive to the application of essential oils directly to the skin (by massaging in).

Ava Williams

Written by Ava Williams

Hello, I'm Ava! I have been writing professionally for just over 15 years. I specialize in writing informative blog posts, breed profiles, pet care product reviews, and pet health and care articles. Prior to and during my work as a writer, I spent about 12 years in the pet care industry. I have experience as a kennel supervisor and professional groomer. I also compete in dog sports with my own dogs. I also have cats, guinea pigs, and rabbits.

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