You are very lucky! I've heard from several vets not to use it with herding dogs like boarder collies, collies, ausies,.... because a high percentage of them have fatal reactions to it. My vet has collies which is why she paid more attention to it. There is no known reason why they react differently though.Also make sure you have a heartworm test BEFORE you use it. Then use once a month. Works great but I have never heard that about a herding dog. My Border Collie gets it and it doesn't hurt her but if that is the case I would make sure it is safe for herding dogs before I use it.
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