Fly Control Strategies That Protect Cattle Productivity

Flies pose a serious risk to cattle health and overall productivity. Several species affect herds through biting, irritation and disease transmission. Their impact grows during warm months when breeding conditions improve. Effective control protects weight gain, milk production and animal welfare.

Impact on cattle productivity
Biting flies such as horn and stable flies cause direct pain and irritation. Horn flies stay on cattle for most of their life cycle and take about 30 blood meals per day. This reduces weight gain and milk production. In severe cases, weaning weights can drop by 4 to 7kg if horn flies are not controlled. Stable flies also draw blood and inject saliva that weakens the immune response, increasing vulnerability to infections.

Non biting flies such as face and house flies also affect herds. House flies breed rapidly in manure. They irritate cattle by feeding on eye and nasal secretions and open wounds. They are mechanical vectors of pathogens linked to pink eye, salmonellosis, campylobacteriosis and mastitis.

Face flies spread pink eye, which remains one of the most common diseases associated with fly irritation. Pink eye raises treatment costs and can cause vision loss in calves and reduced productivity in bulls. Affected cows may be culled early if the condition becomes severe.

Dr Louis Boag of Elanco South Africa says many producers underestimate how much flies harm productivity. He explains that flies also contaminate feed and equipment with microbes carried on their legs or deposited through vomit or faeces. He stresses that producers need proactive control rather than waiting for infestations.

Effective fly control
Dr Boag says effective fly control must target multiple points. Poor management can result in weight losses of up to 9kg per animal. A comprehensive strategy improves outcomes and protects profitability.

The first control point is the fly breeding environment. Fresh manure provides ideal breeding grounds for face flies and horn flies. Feed based larvicides or insect growth regulators added to feed or mineral supplements can kill larvae and stop eggs from hatching. These products work best early in the season when magnesium is added to minerals for grass tetany prevention.

South Africa has several IGRs that fit well into an integrated strategy. These agents interrupt the insect life cycle by preventing growth or development. They target larvae and nymphs, stopping moulting and blocking development into adult flies. Some prevent eggs from hatching. They are specific to insect physiology and pose minimal risk to non target species.

Novaluron is a widely used IGR in liquid larvicides and feed supplements. It disrupts chitin synthesis, which insects need for exoskeleton formation. When cattle ingest feed treated with Novaluron, the compound passes through the digestive system and moves into manure where it destroys fly larvae. This creates long term suppression of emerging fly populations.

Animal protection
The second aspect of control is protecting animals directly. Sprays, pour ons and dips repel face and horn flies and reduce biting. These treatments support grazing animals and help prevent the stress and weight loss linked to infestations. Some products also protect against screwworm, a common threat during warm and wet periods.

House flies in stables, dairies and other buildings can be reduced using insecticides that work through contact and stomach action. These products attract flies and provide long lasting control when applied as water dispersible paints or sprays.

Flies remain a persistent threat, but producers can protect their herds through early action and integrated management. Strong control reduces disease, improves production and supports healthier animals throughout the season.