I just wanted to put my two cents worth in, too. The safest thing out there is herbs. There are many that have been used very successfully for hundreds of years. I use Garlic and Brewers yeast daily and a tincture that I make up myself once a month. I too have a herding dog (a beautiful McNab) and she once got a hold of an empty (so I thought) tube of Ivermectin that I had used to worm my horse. The next day her kidneys completely shut down. I almost lost her. She spent two days in the hospital. After that I started studying herbs for us and our animals. They are so much safer and relatively inexpensive. The thing you need to remember, with any wormer, is timing. You want to give it when the moon is waxing(almost full). And do it 3 days in a row so you kill all stages. I have been doing this for my 2 girls (McNab and Jack Russel) for 2 years now and they are in excellent health.
1 1/2 oz each: Black Walnut (hulls and leaves), Wormwood , and Myrrh.
1 pint vegetable glycerine
Put all into a jar and shake daily for about 2 weeks. Let the herbs settle and pour off the tincture, straining out the herbs through fine cheese cloth.
Give 1/2 tsp. per 20 lbs. 2X daily for 3 days. Repeat in 10 days. Then all you will have to do is once a month. Be sure to also be giving them the Garlic and Brewers (not nutritional yeast) daily. Sorry this turned out so long and thanks for letting me share this. Here's to happy healthy puppies!!!