Treating flies now will reduce the numbers invading the milking parlour and affecting cows’ productivity this summer, according to Charles Chavasse, Area Veterinary Manager at Zoetis.
He said June and July are key months when it comes to fly control and if it turns warm and damp farmers need to prepare for the worst – flies breeding at a rate of a few thousand turning into a million within days. “The weather is changing from warm and dry to warm and damp, and farmers and cows will both be irritated with an increase in flies.
“Flies multiply a lot. One fly will lay a few thousand eggs, so if you have one fly today, who lays a thousand eggs, in 10 days half of these, the females, can lay a thousand eggs each. Don’t wait until the problem is really visible as it is probably too late.”
Flies, he says, are not just an irritant for cows and farmers alike, they also affect cow productivity – reducing how much animals graze and therefore affecting yields and can spread disease, for example summer mastitis.
The best approach, he says, is preventative treatment and farmers need to take action now. “There are various products out there, they all kill the flies that stand on animals after they have been treated, and are not preventive and don’t repel flies. So, it’s important to kill flies off now, before they breed. If you have a few thousand flies now, you will have a few million flies in a few weeks times.”
However, it’s also important that farmers apply the treatment properly – be it spot on or pour on. “A spot on should be applied as a spot, about the size of a fist, on the withers/shoulders of the animal. Pour ons need to be poured down the whole length of the back.” Where it is applied on the animal is important because of how animal hair lies. “All the hair goes backwards from the shoulders and forwards towards the head. So, if you apply a spot on at the back, you would get good protection around the back of the animal, but not around the head and neck.”
Also, he advised that famers should not try to apply spot on when cows are in the milking parlour. “Use the treatment as the cows come out of the parlour, but not in the parlour as you can’t reach the top of their shoulders from the pit. They should be run through a crush as they come out of the parlour. It takes a little more time, but it’s vital to do it right.”
He also said that dairy farmers, with lactating cows, need to be mindful of withhold periods. “Some products that have a 12-hour withhold period and some can not be used on milking cows. Pfizer Spot On, in the yellow box, has a zero milk withhold period.”