Join Date: Apr 2008
Location: Orange County, NC
With one or two horses, we did every 3 months; with 3 horses, we do every 2 months, rotating the wormers as is typical.
With the growing resistance to some wormers, however, there has been recent literature about reducing the frequency of worming.
If you really want to know, the best thing to do is a fecal analysis (though we have never bothered with this). That will tell you if there are any parasites, and what kind, so you know the best wormer to use. I don't know about Australia, but in the U.S., many states will do this for free through the Agriculture Department if you collect and send the speciman, or your vet can certainly do it.
On the sixth day, God created the Quarter Horse.
On the seventh day, he Painted the good ones.