The condition referred to as "hay belly" is often an abdomen infested with encysted small strongyles. Small strongyles are worms that can burrow into the horse’s intestinal lining, forming cysts which remain for up to three years. Unfortunately, fecal analysis cannot be relied upon for diagnosis because it can’t measure worms in the encysted state.
Safe-Guard Power-Dose and Panacur Powerpac are the only FDA approved treatments for all stages of encysted small strongyles. Both treatments contain 5 double-dose syringes of fenbendazole. You should give one syringe (per 1250 lbs) every day for five days in a row. It is important to treat all horses with Power-Dose or Powerpac 1-2 times per year, because regular deworming will not affect the encysted worms.
In many climates, the most advantageous times for use are spring and fall. This eliminates the horse's worm load before and after exposure to pasture. The larvae typically develop on grass, which infects more horses as it is eaten. By treating in the spring, you will help eliminate the worm burden and prevent eggs from being passed out in manure. Treatment in the fall addresses the parasites acquired from grass. Power-Dose or Powerpac can also be used to relieve a horse’s worm burden prior to starting horses on a daily dewormer. Lori H