Anytime you ask people about "natural dewormers", you have to look at the answers very critically because there can be lots of factors that affect the validity of their opinions. For example, did they have fecal egg counts done on their horse(s) to determine the parasite load before deworming and then again afterwards to see if the parasite load was effectively treated? Getting samples done at both of those times is important because horses have varying levels of resistance to parasites so if you treated a horse that is resistant and normally carries a very small parasite load and then just checked a fecal after deworming you would wrongly assume that the "natural dewormer" did something because the fecal was low or negative. Or did they just base their opinion on "he didn't look like he had parasites". When was the last time they used a chemical dewormer before using the natural dewormer? Because their fecal results may hae been due to the egg reappearance period from the chemical not having passed. What kind of environment/management situation was the horse in? A dry-lotted horse is going to generally have a much much lower parasite load than a horse that is sharing a pasture with a bunch of other horses and no feces removal.
Since parasites are a risk factor for colic, can cause damage to the GI tract, liver, blood vessels, and other organs during their larval migrations, etc my belief is you are better off using something you know works.
As for ordering from say the US and having it shipped to Canada. The overall price may be lower, but shipping may eat you alive. I just had books shipped down from Canada and was amazed at the fees charged by the postal service.
So, check the price and shipping to be sure you are getting the better deal.
Licensed Veterinary Technician