It is tempting to turn horses out into spring pastures at the first sight of green grass, especially after a long winter. However, spring grazing should be introduced slowly and delayed until grasses reach 6 to 8″ to optimize both the health of the horse and pasture. When horse pastures reach 6 to 8″, begin grazing for 15 minutes, increasing the grazing time each day by 15 minutes until 5 hours of consecutive grazing is reached. After that, unrestricted grazing can occur.
Why is this recommendation so important? Even though hay and pasture are both forms of forages, there are significant differences. Dried hay is approximately 15% moisture compared to fresh pasture that is 85% moisture. The horse is a hind-gut, fermenting herbivore that relies extensively on the microbes present in its gastrointestinal tract to be able to process forages. The microbes are a mix of different organisms that work together to the benefit of the horse. If the feedstuffs the microbes are utilizing change suddenly, there may be too little time for the microbial populations to adjust to the change. Instead, large numbers of them die, while others flourish, setting up a situation where toxins may be absorbed by the horse, resulting in digestive dysfunction and possibly colic. A gradual change from one feedstuff to another provides enough time for the microbial populations to adjust.
Additionally, pasture grasses need sufficient growth before grazing is allowed. Photosynthesis (the process of converting solar energy to chemical energy) occurs mainly within the leaves of plants. If the leaves are grazed too early (prior to 6″ tall) or too often, plants can lose vigor, competitiveness, and root structure due to the lack of photosynthetic ability. This will lead to eventual die back and overgrazed areas being replaced by undesirable plant species or weeds. Grazing should cease when forages have been grazed down to 3 to 4 inches. At this time, move horses to another paddock or a dry lot. Grazing can resume when grasses regrow to 6 to 8″. On average, about 2 acres of well-managed pasture can provide the forage needs for one horse during the grazing season.
It is critical to slowly introduce horses to spring pastures. So, the following is worth repeating, when horse pastures reach 6 to 8″, begin grazing for 15 minutes, increasing the grazing time by 15 minutes each day until 5 hours of consecutive grazing is reached. Following this recommendation will help ensure both horse and pasture health.
Author and photo credit: Krishona Martinson, PhD, University of Minnesota