Hi
I am not facing any mosquito problem, however during day time we have fly problem.
To tackle, we are spraying the cow with a chemical called Cypermethrin, which is available in any veterniary drug store. There are other solutions like spraying neem oil, but the best result we have got is with the chemical one, and till date no side effects on the cow.
The effect of the chemical lasts for some 6-7 days. Since we wash our cows weekly, we spray after they are washed.
Nikhil