10/28/2026
Grass isn’t the same feed from spring to fall, and in a state like Iowa, where weather swings shape forage quality, understanding those seasonal nutrient changes is one of the most important parts of managing horses on pasture. What your horses get from the grass in April is very different from what they get in August or October, and adjusting management around those shifts keeps them healthier, better conditioned, and nutritionally balanced.
Spring grass is the richest.
As soon as pastures green up, cool‑season grasses like brome, orchardgrass, and fescue explode with growth. This early grass is high in moisture, high in protein, and high in sugar. For easy keepers or horses prone to laminitis, those spring sugar spikes can be risky. For broodmares and growing foals, the protein and energy are beneficial, but turnout still needs to be controlled to avoid overconsumption. Spring grass is nutrient‑dense but can be overwhelming if not managed carefully.
Summer changes everything.
By mid‑summer, Iowa heat slows cool‑season grasses down. Growth tapers, moisture drops, and nutrient density shifts. Protein levels fall, fiber increases, and non‑structural carbohydrates (NSC) often stabilize. Horses may need supplemental hay or a ration balancer to maintain condition, especially lactating mares or young stock. Pasture quality becomes more variable depending on rainfall, wet summers keep grass softer and more nutritious, while dry spells push it toward stemmy, low‑energy forage.
Late summer and early fall bring another spike.
When temperatures cool again, Iowa pastures often experience a fall regrowth. This grass is similar to spring forage: fresh, lush, and higher in sugars. Horses tend to gain easily during this period, and metabolic horses need careful monitoring. Even though the grass looks “light,” its nutrient profile can be deceptively rich.
Fall into early winter shifts grass into maintenance mode.
As frost hits, grass stops growing and nutrient levels drop sharply. Protein falls, digestibility decreases, and horses rely more heavily on hay. Pasture becomes a filler rather than a primary nutrient source. This is when mineral balance matters most, Iowa soils can be naturally low in certain trace minerals, so providing a consistent mineral program helps fill the gaps left by dormant forage.
Understanding these seasonal nutrient swings helps you make better decisions for your herd: adjusting turnout, supplementing correctly, protecting metabolic horses, and supporting mares and foals through growth and breeding cycles. Grass is always changing, and good management changes with it.
