Why Your Horse's Gut Health Influences their Fly Magnet Status!
Your Equine Answers on Horse Care in Fly Season
What is the best fly spray for horses is one of the most asked questions in the equestrian world as we all try to avoid the summer swarms! But have you ever wondered why some horses are more attractive to the flies than others? There is growing interest in the link between gut health and how attractive a horse is to flies - and it’s not as far-fetched as it sounds!
Horses with poor digestive health often produce more pungent droppings, altered sweat or skin odours, and may even suffer from skin irritation or hypersensitivities, all of which can draw in flies and midges.
An imbalanced gut can lead to inefficient digestion, meaning more undigested nutrients are excreted — a feast for flies! Additionally, because gut health supports immune function, a compromised gut may contribute to inflammatory skin conditions like sweet itch, further increasing insect attraction. By supporting your horse’s digestive system - particularly the hindgut - you can help improve overall wellbeing and potentially reduce how much of a target they become during fly season.
Although it's an emerging area and not yet fully understood, here's how the connection between gut health and how attractive a horse is to flies may work and why it is important to consider these before simply reaching for the fly spray:
---
Odour and Gut Health
A horse’s skin, sweat, and manure all contribute to their individual scent profile — and that is what attracts flies. Poor gut health can lead to:
- Undigested nutrients in manure may make it more attractive to flies
- Increased fermentation and gas, altering the horse’s body odour
- Changes in skin microbiome, potentially influencing scent
Healthier guts typically lead to better digestion and fewer strong or abnormal odours — lessening a horse's "fly magnet" status. Look at the horses in your field, do you notice one is more attractive to flies than others? Have a look at their droppings and see if you can notice any differences with the other horse’s.
---
Manure Quality
Horses with an imbalanced gut microbiome may produce looser or smellier droppings — which:
- Attract more flies for longer periods
- Increase the fly load in the paddock or stable area
Well-digested manure (i.e. from a healthy gut) tends to be less pungent and less attractive to flies. We have all poo picked and noticed those piles that are swarming with flies compared to others. Consider which horse these are coming from and monitor to see if there is a pattern of sustained loose or smelly manure which may indicate a problem.
---
Immune Response and Gut Health
Because approximately 70% of a horse’s immune system resides in the gut-associated lymphoid tissue (GALT), any imbalance in hindgut health can result in heightened immune reactivity. When the gut microbiome is compromised—due to high-starch diets, stress, medication, or lack of forage diversity—it can lead to leaky gut and systemic inflammation. This not only affects digestion and nutrient uptake but may also contribute to overactive immune responses at the skin level, such as increased sensitivity to fly bites or allergens. By restoring gut microbial balance and strengthening the intestinal barrier with functional ingredients like prebiotics and plant polyphenols, horses may experience improved immune tolerance, less skin irritation, and reduced attraction to midges or biting insects. This link between gut and skin health is a key reason why addressing digestive wellness can play a role in managing seasonal skin flare-ups like sweet itch or hives
---
Internal Parasites
While technically not an issue of "gut health" alone, horses with higher parasitic burdens—often linked to poor digestive balance, stress, or suboptimal pasture hygiene—may be more attractive to certain species of flies, such as botflies.
Parasitic infestations can alter a horse’s scent profile through changes in microbial fermentation and excretions (urine, manure, sweat), potentially making them more appealing to certain insects. A compromised gut environment, particularly one affected by high worm burdens, has also been linked to impaired immunity, inflammation, and changes in the gut-lung-skin axis, all of which may increase vulnerability to fly-related irritation and secondary skin issues.
Additionally, research has shown that botfly larvae can significantly impact the gastric mucosa, reducing gastric function and contributing to ulcer-like conditions—further tying parasite management to digestive and overall wellness.
Key Take- Aways
While not a direct cause-effect relationship, poor gut health contributes to fly attraction through:
- Odour changes
- Poor manure quality
- Immune dysregulation
- Skin irritation
Improving gut health — e.g., with targeted prebiotics, hindgut support like Equell Gut Food, and appropriate diverse forage — can all help to reduce a horse’s attractiveness to flies and make their lives (and yours) that little bit easier. Natural fly sprays for horses and insect repellents are a useful addition but optimising your horse’s gut health will strengthen their natural defences against those pesky insects!
CLICK TO SHOP EQUELL GUT FOOD NOW - FOR OPTIMAL HINDGUT HEALTH!
