You mean the horse wormer paste or the drench or injectable?
I've used the huge paste tubes from Safeguard (can't remember the active ingredient) for everything, from dogs to cattle and horses. Dosing is not as critical and it is nearly impossible to over dose an animal
my buddy has done it that way for years and years...my guess is because he has big syringes for his cows and they dont have fine measurements on it..and the glycol is sweet and dogs readily eat it...i mix it on scraps or canned food and i know it got gobbled up..
ive seen some really picky dogs when it comes to wormers and medicines..others will eat anything and keep it down...
I like the external meds for Heart Worm and most all other paracites also. Have been using it for many many years now, with 100% success. It is more expensive than Ivermic, but safer for the dogs.