Spring grazing and horses

Krishona Martinson
University of Minnesota Extension
A horse grazing in a pasture.

Question: In a recent Facebook post about spring grazing, you recommended starting to graze when grasses reach 6-8” tall and slowly initiating horses to spring pasture in 15 minute increments. What about horses that are in pasture 24-7? How do you manage these horses? 

Answer: Our recommendations do include the slow initiation to spring pasture and waiting to start grazing until the grasses reach 6-8” tall. This assumes you are in a northern location with distinct growing seasons, including a winter that results in the reliance on hay. Following these management recommendations is best achieved when facilities have and use a designated dry lot and are intended to reduce risk, for both the pasture and horses. 

From a horse perspective, it’s much riskier to not have a transition period between feedstuffs. For example, horses currently being fed hay should be slowly transitioned to spring pasture to reduce the risk of colic and laminitis. This is regardless of current housing (e.g. dry lot or dormant pasture). This transition is key to help gut microbes adjust, which assist with digestion. Without an adjustment period, these specialized gut microbes can die off after a rapid diet switch, which can result in the release of toxins and possible bouts of laminitis and colic. This risk might be less for fit, healthy horses, but is thought to increase for older, overweight, or horses with a history of colic or laminitis. Additionally, new pasture growth (≤2”) is extremely high in nonstructural carbohydrates. This might not be an issue for fit, healthy horses, but may be an issue for overweight horses or ones with a history of laminitis. Having and utilizing a dry lot makes managing the transition from winter hay feeding to spring pasture grazing much easier.

From a pasture perspective, continuous grazing will eventually lead to dead spots and weed invasion, especially if there are fewer than 2 acres of pasture per horse (this recommendation reflects generalized Midwest stocking rates). All pasture grasses and legumes need leaf area to intercept sunlight to support growth. If the leaf area is constantly removed by grazing, the plant utilizes root reserve to support growth. However, root reserves will eventually become depleted, and when combined with no leaf growth due to overgrazing, the plants die and weeds invade. Allowing the grasses to grow to 6-8” in the spring allows the root reserves to stock up after the rapid spring growth and also allows time for the nonstructural carbohydrates to level out and become more “normal.” The importance of leaves to intercept sunlight to support growth is also why we recommend that pastures never be grazed or mowed lower than 3.” 

We realize these management strategies can be challenging to implement in certain scenarios. However, they are rooted in research-based information with the goal of reducing the risk of unintended negative consequences to both the horse and pasture.