Preparing for spring and summer grazing

Unique weather this year and limited soil moisture in many regions of the state, require us to approach grazing differently this spring. Here is what you need to know before opening your pasture gates.

Understand regrowth of pastures in spring

The regrowth of grasses and legumes in the spring or after grazing follows a general growth curve. Forage yield starts low because the plants' energy stores (carbohydrates) and leaf area are small. As the leaf area increases, the plant captures sunlight to produce energy (photosynthesis), which recharges the root energy stores. Root and crown mass and tillering increases. Forage yield increases rapidly until flowering; the proportion of stems in the forage increases and flowering begins. At flowering stages, energy stores have been recharged, which can allow more rapid regrowth of plants following grazing. In most of Minnesota, grasses and legumes typically begin flowering in late May in response to increasing length of daylight (photoperiod).

Above average air temperatures and no late-winter snow cover have led to early leafy growth of pasture legumes and grasses. Spring leafy vegetative growth will be unusually long this year because grasses and legumes will likely not flower until mid-late May based on daylight. With normal spring rainfall, this should provide extra grazing time this year. Every year it is important to consider routine pasture management practices, such as rotational grazing, and to observe recommended pasture stocking rates to sustain and improve pasture productivity.

Delay grazing

Even though grass and legumes will “green-up” earlier than expected this year, resist putting your horses on pasture too soon. Only start grazing when grasses and legumes have enough leaf growth (height of 6 to 8 inches) to begin replenishing carbohydrates stores used during the winter. Stop grazing before your horses eat all the stems and leaves and plant heights reach 3 to 4 inches. 

Overgrazing in the early spring will deplete energy stores, slow regrowth, weaken plants, and reduce yields later in the season. It can also affect root and rhizome growth (underground stems) and thin stands are prone to weed invasion. For plants stressed due to winter injury or soil heaving, longer spring growth periods will help with plant persistence.

Additionally, hoof traffic by horses in the early spring can lead to soil compaction and be especially harmful to stand density of legumes and bunch grasses (e.g., orchardgrass, meadow fescue). Root systems of these plants may be weak or displaced by freezing or thawing cycles of the soil. 

Slowly acclimate horses to pasture 

Keep the horses off pastures until the ground is firm and the grass and legumes reach sufficient heights. Ease horses onto pastures in 15-minute, daily increments (15 minutes the first day, 30 minutes the second day, etc.) until you reach 5 hours of grazing. Acclimating the horses to pasture will take several weeks. After reaching 5 hours, your horses can graze continuously as long as enough grass and legumes are available. Gradual transitions in diet provide microbes in the gut time to adjust, which reduces the risk of laminitis or colic.

Allow pastures sufficient rest

With early spring grazing, maintaining rest periods and observing plant height minimums before re-grazing is key.

• Continuous grazing of plants and removal of too much foliage will not allow plants to recharge energy stores.
• In a spring with adequate moisture and ideal temperatures, rest periods as short as 14 days are adequate for cool season grasses to reach ideal regrowth heights.
• During summer, rest periods of at least 30 days are common to reach the same plant regrowth heights.
• For alfalfa-grass mixtures, rest periods should be about 3 to 4 weeks because alfalfa (and red clover) is more prone to using up its root energy stores. For plants stressed due to winter injury or drought, longer rest periods will help with plant persistence.