CORVALLIS, Ore. – Horses that graze on small acreages in the winter can create an unhealthy field of mud that not only sickens the horses but can pollute streams and groundwater. With careful management, however, it is possible to tend a good grass cover that keeps weeds down, water clean and horses healthy.
In pastures of 10 acres or less, rain and mud make an unhealthy life for horses. They can suffer from mud fever (scratches), hoof and sole cracks and internal parasitic infections from manure.
"Mud harbors bacteria and fungal organisms that can infect horses and pollute streams, groundwater and household wells,” explained Melissa Fery, small farms faculty member with the Oregon State University Extension Service.
A 24-page booklet from the OSU Extension Service spells out how to keep small-acreage horse pastures healthy and at the same time protect water quality. "Managing Small-Acreage Horse Farms" (EC 1558) is free online, or can be purchased for $4, plus shipping and handling, by calling 800-561-6719.
Fery recommends the following to help horses get through the rainy season on small acreages:
• Don't overgraze or overstock your area. Rotate grazing and allow pastures to rest. In western Oregon or Washington, a mare and a foal require about two acres for grazing. A minimum of one acre per horse is required to cycle nutrients from manure and urine and to provide adequate space for exercise. The amount varies depending on the amount and frequency of rain and how much the horse gets supplemental food and is exercised elsewhere.
• Keep animals off wet pastures, where they can overgraze and trample grass and thus create mud and compacted soil. The vegetation is needed to filter sediments and use nutrients from manure.
• Create a "sacrifice area," a separate paddock to keep animals off wet pastures. This restricts grazing impacts to one area and saves pastures during wet months. Paddocks can be prepared with "hog fuel" wood shavings, chips or gravel.
• Use grass or vegetation "buffer strips" around your sacrifice area. Grass and other plants filter sediments and use excess nutrients.
• Install rain gutters and downspouts on farm buildings to direct water away from paddocks.
• Cover manure piles with a tarp or roof to prevent rain from leaching away nutrients and microorganisms into water. Or better yet, compost your horse manure.