Do You Need a Grazing System?
Cathie Erichsen Arychuk, P.Ag.
Bison Production Specialist
Grazing systems balance livestock needs with plant needs to give optimum pasture productivity. Grazing systems are a planned approach to managing bison on pasture by adjust grazing periods and rest periods.
Do You Need a Grazing System?
Ranchers are always interested in grazing systems, especially those that might make them more money. A grazing system is simply a planned approach to managing livestock on pasture. Some grazing systems are very simple. Some are quite involved. Which one will work best for you will depend on where you are in Alberta, the climate there, the forage plants on the pasture, and your management.
The two keys to a good grazing system are a rest and recovery period for the plants, and the length of time livestock stay on each pasture. A good grazing system allows plants to recover after defoliation. This recovery time has to occur during the growing season. The plant can’t regrow and replenish root supplies when the ground is frozen, or when no water is available for growth. The rest period is what keeps the plants in your pasture healthy and productive. The length of the rest period varies with plant species and with climate. A tame grass/legume pasture that gets 18" of annual precipitation may recover from grazing in 60 days, and be available to regraze. A native pasture that gets 14" of annual precipitation may need 12 to 18 months to recover.
How long the bison remain in the pasture is also important. Ideally, you want animals to bite each plant only once while they are in the pasture. When a plant is grazed again before it recovers from the first grazing, it is weakened. Where plant regrowth is rapid, 5 to 10 days in a pasture may be as long as you want animals to stay. Where plants grow more slowly, bison can stay on a pasture longer without regrazing plants.
What grazing systems are popular? Continuous grazing is quite common in Alberta. In a continuous grazing system, bison graze one field for the entire grazing season, often May to October. This can result in parts of the field or specific plants being repeatedly grazed all summer. Stocking rates should be kept at a moderate level to reduce damage to the pasture. However, where the growing season is very short, such a native prairie in southeastern Alberta, this grazing system can be quite effective.
Rotational grazing systems are those where we move stock between two or more fields, to allow plants to recover after grazing. Rotational grazing systems can be very intensive. Some dairy herds are moved twice a day. However, they can also be much less involved. For an intensive system to work, the climate and plants must allow regrowth on the pasture so you can graze more than once in the growing season. In the brown and dark brown soil zones, where regrowth is uncommon, less intensive rotational grazing systems work well. In this area, the growing season can be very short, often only May and June. Plants may need a year or more to recover from grazing.
Different grazing systems achieve different goals. The key is to make sure plants get adequate time to recover from grazing before the animals bite them again. This will help maintain healthy, productive pastures.