How feeding in a Porta-Grazer can help
When using a Porta-Grazer the rotating pan lifts the hay up to the horse. This allows the horse to tear off a bite without being able to sort thru the hay. Each bite is pulled directly into the mouth. The dust, sand, pollens and mold are shaken loose. Which works its way to the bottom of the barrel. There it is collected in a trough out of the horses reach to be discarded later.
You can also rinse or soak the hay in the Porta-Grazer. All models have a drain plug.