Keep fly control up to scratch

Just two horse flies exceed the economic nuisance threshold for cows at grass, whereas severe swarms of stable flies can cause reductions in milk yield of up to 25%.

Keeping fly control up to scratch when cows are at grass is as important for the irritant factor as it is for minimising the impact of fly borne diseases such as New Forest Eye and summer mastitis, warns Schering-Plough Animal Health veterinary adviser Andrew Montgomery.

"Even if as few as six stable flies land on each of a cow's legs it could have a negative impact on production. The economic threshold for stable flies on cattle is as low as 25 flies per animal per day and researchers have shown that a population of only 50 stable flies per calf reduced weight gains by 0.9kg/day over a 100-day period. Unfortunately, swarms of 200-250 flies per animal are not uncommon and the stable fly's bite is so painful that it can easily disrupt animal feeding patterns, leading to sub optimal performance," he says.

Because of this disruptive effect, Andrew Montgomery says what farmers need is an insecticide product that can cover the whole animal fast.

"The active insecticide ingredient in Coopers Spot On spreads over the whole body, including the head, belly, legs and rump within two hours of a single, 10ml spot application on the back of the animal," he points out.

"Deltamethrin-based insecticides are undoubtedly extremely effective fly control products. "Deltamethrin is over four times more potent than its nearest rival, with Coopers Spot On containing the highest concentration of this active ingredient. However, the type of deltamethrin carrier is crucially important. The use of a proven oil-based carrier ensures the insecticide spreads quickly and effectively all over the animal, and doesn't just stay on the back where it has been applied. Trials with Coopers Spot On show that it kills flies, even on the belly and legs, within two hours of application," he stresses.