Note: I wrote this article for the American Mule Association newsletter last year - thought it might be of interest here!
As a mule owner who also happens to be a commercial sheep producer, I try to pay close attention to the health of my pastures. While our mules get most of their nutritional intake from hay, we do provide pasture periodically during the year – both as a supplemental feed source and for exercise. We try to maintain quality pastures – both for the benefit of our mules and for the protection of soil health and water quality. A basic understanding of the interaction between soil, water, pasture plants and our animals is key to our success as pasture managers.
Perhaps because we make part of our living from grazing sheep, I view myself as a grass farmer who harvests his crop with livestock (sheep and mules, in our case). This philosophical approach means that we try to create the conditions favorable to desirable grass plants AND unfavorable to weeds (a weed, by my definition, is any plant that is growing where I don’t want it to grow). To create these conditions, we can manage a few basic functions: stocking rate (the number of animals), stock density (the number of animals per unit of pasture), rest from grazing, and timing of grazing.
Our pastures are unirrigated annual rangelands – that means they are dominated by annual grasses that complete their entire life cycle (germination, growth, reproduction and death) each year. Typically, we’ll get enough rainfall in the autumn to germinate our pastures. If these rains come early in October (when the air and soil temperatures are still favorable to grass growth), we’ll get fairly substantial growth before the colder weather and winter dormancy set in. Usually in December, shorter days and colder temperatures will slow or stop grass growth. With adequate rainfall, longer days and warmer temperatures in late February will bring our pastures out dormancy, and rapid grass growth will begin sometime in March. As temperatures continue to warm and the spring rains diminish, our annual grasses will begin to mature (or head out) and make seed. As these plants begin to turn brown, their palatability and nutritional value diminish.
Grazing animals have three basic impacts on pasture plants. First, obviously, they consume plants through grazing. Not all grazing is equal, however – we’ve probably all noticed that horses graze differently than sheep or cows, for example. I’ve also noticed that mules graze differently than horses – mules seem to enjoy a wider variety of forage than horses do. These grazing differences are both physiological and behavioral – horses and mules like different plants than cows and sheep, and their mouths are constructed differently as well. The second impact is trampling – hoof action impacts both plants and the underlying soil. Finally, grazing animals cycle nutrients by depositing manure and urine on the soil surface. These areas of defecation and urination create what animal scientists call “zones of repugnance” (I love the term!) – we’ve probably all also noticed that our mules won’t eat around a manure pile for several months. This behavior has evolved as a disease-avoidance mechanism for all grazing animals.
With management, these impacts can have a positive effect on pasture health as well as on soil and water quality. By resting our pastures, we allow grazed plants to regrow and out-compete undesirable weeds. By managing trampling and manure/urine deposition, we can cycle nutrients and carbon through our soils. By leaving enough plant cover at the end of the growing season, we can ensure that run-off water is filtered before it reaches ponds or creeks and that we have a microclimate suitable for germination with the fall rain.
Without management (usually through season-long grazing and no rest for our pastures), these impacts can have a negative effect on pasture health, soil stability and water quality. Horses and mules will overgraze the plants they like, allowing weeds (like yellow starthistle) to thrive. Trampling when our soils are too wet can create soil compaction and bare soil – which further encourages weed growth and causes erosion. In addition, bare soils are unable to filter pathogens and other pollutants from our pastures – and these pollutants end up in ponds and streams.
Finally, overgrazing is a function of time rather than animal numbers. Overgrazing can occur when we leave animals in a pasture too long – they take a second bite from a plant before it has had enough time to recover. Overgrazing can also happen when we cheat the rest period – that is, when we put animals back a pasture before the plants have fully recovered from the previous grazing. In either case, we risk killing the plants we want and providing favorable conditions for more weeds.
Here’s what we do to manage our mule/horse pastures: We keep our animals off our pastures entirely during the fall germination/growth period. We want our pasture grasses to establish strong root systems during this time and for them to become well-established prior to the onset of heavier winter rains (which will help prevent erosion). During the fall and winter, we feed hay in small paddocks that are surrounded by grass (as a buffer that filters our run-off). Once rapid growth begins in late winter or early spring, we’ll begin turning horses and mules out onto our pastures for a few hours each day. We treat these like feeding periods – if it typically takes our mules 2 hours to eat their hay, we’ll turn them out on pasture for two hours in the morning or evening (sometimes both). We don’t leave them out around the clock, and we don’t turn them out if the soils are saturated (which can accelerate compaction). We’ll continue to do this until the grasses start to mature. At that point, we cease grazing with the equines. In the late spring and early summer, when undesirable plants like yellow starthistle and mustard begin to mature, we’ll try to put sheep on our pastures to manage these weeds. As an alternative, you might consider hand-pulling these weeds or using an approved chemical application.
For more information on managing your mule pastures, check out the following web resources: