As the summer heat gives way to the cooler fall weather and the light of the day gets shorter, our pastures begin to change.

Interestingly, the changes we observe in our fall pastures are often similar to the changes we observe during the spring - the brown, dormant plants give way to young, green shoots of grass and other plants that begin to emerge from the soil.

Generally, most warm-season forages do well when soil temperatures are above 60 °F (16 °C) and ambient temperatures are above 85 °F (29 °C). Conversely, cool-season forages do well when soil temperatures drop below 50 °F (10 °C) and ambient temperatures average 65 °F (18 °C). Thus, during the transition into fall, our warm-season forages begin to stop growing and die off. Yet, our cool-season plants have yet to emerge or are not mature enough to withstand horses grazing.

This transition period in the fall is a time where most pastures are not productive enough to support grazing. Thus, it would be advisable to take your horses off your pastures and place them into a sacrificial area to be fed hay. This allows enough time for your fall pastures to be established. You can learn more about this strategy and other pasture management tips in our Summer Pasture Management article.

There are many factors that will determine which plants will emerge in the fall and begin to grow, such as:

  • Location: higher latitudes (northern states) will experience earlier die off of warm-season plants and earlier emergence of cool-season plants compared to lower latitudes (southern states).
  • Temperature: similar to location, cooler temperatures will accelerate the die off of warm-season forages and emergence of cool-season forages.
  • Elevation: can be tied into temperature with higher elevations associated with cooler weather.
  • Moisture: locations with more rainfall in the fall can expect more productivity in their pastures compared to more arid regions.

As stated above, our cool-season forages begin to emerge with cooler soil and ambient temperatures. For review, here are some typical cool season grass forages and their characteristics for horses in North America:

  • Kentucky Bluegrass
    • Optimal growth when temperatures range 60 to 85°F (15 to 29°C)
    • Growth halts when temperatures reach near freezing 32°F (0°C).
    • High nutritional value with range Crude Protein 12-17% and Digestible Energy 0.86 to 1.04 Mcal/lb.
  • Ryegrass
    • Optimal growth when temperatures range 68 to 86°F (20 to 30°C).
    • Growth halts when temperatures drop below 41°F (5 °C).
    • Moderate to high nutritional value with range CP 11-17% and DE 0.82 to 1.0 Mcal/lb.
  • Timothy
    • Optimal growth when temperatures range 65 to 72°F (18 to 22°C).
    • Growth halts when temperatures drop below 50 °F (10°C).
    • Moderate nutritional value with range CP 11-15% and DE from 0.82 to 1.04 Mcal/lb.

Typical legume forages in North America and their characteristics for horses include:

  • Alfalfa
    • Optimal growth when temperatures range 65 to 80°F (18 to 27°C).
    • Growth halts when temperatures drop below 40°F (4°C).
    • High nutritional value with range CP 18-22% and DE from 1.0 to 1.2 Mcal/lb.
  • Clover (White)
    • Optimal growth when temperatures range 70 to 77°F (21 to 25°C).
    • Growth halts when temperatures drop below 40°F (4°C).
    • High nutritional value with range CP 15-22% and DE from 1.0 to 1.3 Mcal/lb.

As the new growth of cool-season forages begins to emerge, the principles of our Transitioning Your Horse to Spring article would also apply. Briefly, young forages are higher in sugars/starches (non-structural carbohydrates), protein and moisture content. Because of this, horses should slowly be transitioned onto a green, lush pasture to limit digestive upset. Additionally, immature plants are more palatable to a horse and prone to overgrazing. Added with the fact that horses graze plants down close to their roots, if they are let on a pasture too early, this will lead to plant die off. Thus, horses should only be allowed onto a pasture when plants reach at least 6 inches (15 cm).

Another concern with fall pastures is when an area suffers its first freezing night when temperatures drop below 32°F (0°C), often called the “first killing frost.” This can cause both grass and legume plants to spike in nonstructural carbohydrates. Thus, an overload of nonstructural carbohydrates in the gut can lead to laminitis, colic, or cause difficulty with horses suffering from metabolic disorders. It is generally recommended that after this first frost, horses are kept off the pasture for a week and fed hay in a sacrificial area. Subsequent freezing nights are less of a concern.

To maintain pasture productivity in the fall and heading into the spring, there are some other management strategies owners can practice:

  • Seeding pastures can be helpful in promoting productivity. When to seed will depend on your location.
  • Submit a soil sample to check to see which fertilizers you may need.
  • Applying nitrogen will assist in plant productivity in the fall and survivability in winter.
  • Practice weed control.

If you have any concerns about how to manage your pastures and its productivity, it is always advisable to contact your local extension office. They will know how best to advise you in your region of the world. If you have any other questions, please feel free to contact us!
 

Chris J. Mortensen, Ph.D.