Flies may seem harmless, but their impact on cattle is greater than is often thought. They cause stress, spread germs and can lead to unnoticed production losses and additional costs. Read this blog to find out why this problem deserves more attention.

Stress Caused by Flies

Flies such as stable flies (Stomoxys calcitrans), horseflies (Tabanidae), and face flies (Musca autumnalis) are a major source of stress for cattle, especially during the warm months when their populations peak. These insects cause constant irritation, leading to noticeable changes in behaviour. Cattle try to fend them off by repeatedly swishing their tails, shaking their heads and avoiding areas where flies are present.

This ongoing activity increases the animals’ energy expenditure, reduces feed intake, and ultimately results in lower milk production and slower growth. Fly-induced stress can also weaken the immune system, leaving cattle more susceptible to disease.

Disease Transmission

Flies also play a key role in spreading infections and diseases. Stable flies are notorious for their ability to transmit pathogens such as Staphylococcus aureus, a bacterium that can cause mastitis (udder inflammation). Face flies, on the other hand, primarily target the mucous membranes of the eyes, nose, and mouth. They are highly efficient vectors of the bacteria responsible for conjunctivitis in cattle.

In addition to the nuisance caused by flies, it is also important to pay attention to other small insects around the farm. Some diseases in cattle are not transmitted directly from animal to animal, but through insects. Bluetongue is a well-known example. This viral disease is transmitted by biting midges (Culicoides), small blood-sucking insects that can spread the virus from one animal to another through their bite.

When a midge feeds on the blood of an infected animal, the virus can develop within the insect. During a subsequent bite, the virus can then be transmitted to another cow, sheep or goat. As a result, outbreaks can spread quickly when the population of these insects increases, particularly during warm and humid periods.

This shows that effective insect control around the barn and pasture is an important part of overall herd health management on the farm.

Secondaire infections

Blood-feeding flies, such as horseflies, inflict painful bites that damage the skin. These small wounds serve as entry points for bacteria and other pathogens, leading to problems that can range from mild skin irritation to severe infections such as abscesses or lymphangitis.

In addition, flies can cause myiasis, a serious condition in which they lay eggs in wounds or on intact skin. The emerging larvae feed on tissue, causing necrosis, severe inflammation, intense pain, and extensive tissue damage. Without prompt treatment, myiasis can sometimes even be fatal.

Economic Consequences

The combined effects of stress, disease transmission, and secondary infections lead to substantial economic losses for cattle operations. These losses include reduced milk production, slower growth, and higher costs for treatment, labour, and herd management.

Studies estimate that fly infestations can cost the livestock sector millions of euros every year, making their control not just a welfare issue but a financial necessity.

Management and Prevention

Controlling flies requires a systematic and integrated approach. Preventive measures are key to keeping fly populations in check and protecting the health of the herd:

• Hygiene: Regularly clean barns, remove manure, replace bedding, and eliminate feed residues to eliminate fly breeding sites.
• Insecticides and repellents: Choose safe, responsible treatments, preferably natural or eco-friendly options, to reduce fly populations.
• Mechanical protection: Use fly traps, screens, and ventilation systems to capture flies or prevent them from entering barns.
• Monitoring and evaluation: Conduct regular inspections and track fly populations to intervene before infestations become sever

Conclusion

Flies have a significant impact on the health and welfare of cattle. By acting as stressors and disease vectors, they not only compromise the well-being of the animals but also reduce farm profitability. Implementing a comprehensive, integrated fly management strategy is essential to minimize these negative effects and safeguard both herd health and economic performance.