Design a Winter Grazing Pasture for Bison

Cathie Erichsen Arychuk, P.Ag.
Bison Production Specialist
AAFRD, Fairview

Summary

Bison willingly graze through the snow on winter pasture.  An effective winter grazing pasture provides adequate forage quantity and quality for the bison through the winter.  Proper management helps make winter grazing effective.

Design a Winter Grazing Pasture for Bison

One of the natural advantages of bison is their adaptation to North American winters.  Bison can manage well on pasture in the winter.  Wild bison herds grazed year round.  They also used a rotational grazing system to optimize forage availability in the winter.  Most bison in western Canada spent the summer on the prairies, then in fall moved north and west into the Parkland and Foothills areas.   These areas were only lightly grazed in the summer, allowing grass to accumulate for winter use.  These areas also offered shelter from winter storms, a higher volume and quality of forage and snow as a water source.

Forage quality drops after the growing season, but bison are well adapted to graze through snow and use this lower quality forage in the winter.  Bison digest poor quality forage better than cattle, and use low protein feeds more efficiently.  A bison's metabolic rate also drops from summer to winter.  As a result, feed quantity and quality required are somewhat lower in winter.  This is likely an adaptation allowing winter survival in North America.  Animal requirements adjust to match the feed available.  Bison are also very adapted to cold weather.  Beef cows require additional nutrients for heat production at temperatures below about _20oC.  Weaned bison calves have a lower critical temperature, the temperature where nutrients are required for heat production, of _30oC.  Adult bison are likely even lower than this.  As a result, they can survive on feed available on pasture during the winter.

For winter grazing to work, forage of sufficient quality and quantity to support the herd must be available on pasture.  Winter grazing has to be done as part of a planned grazing system.  Select your winter pasture in the spring.  Manage grazing on this pasture through the summer to ensure that an adequate supply of good quality feed will be available to the animals in the winter.  For pastures in black and gray wooded soil zones, you may want to harvest the forage by either grazing or haying in the summer.  Second growth of grasses contains more nutrients than mature forages when stockpiled on pasture.  Clipping fields and allowing them to regrow will significantly improve forage quality.  The best time for clipping in preparation for winter grazing will vary from year to year, and also with forage species used.  However, clipping in July usually gives the best compromise between leaving enough time for regrowth to levels that will support the herd and maintaining a good quality feed supply.  After clipping, winter pastures should be rested to allow forage to accumulate for winter use.

Another consideration for winter pasture is the forage species used.  Some grasses and legumes maintain their quality better into the winter, and are more accessible for grazing.  Grasses like creeping red fescue and meadow brome, which grow as bunches of basal leaves, will provide more nutritious winter forage than grasses like timothy and smooth brome, where the leaves blow off the stem.   The leaves of bunch grasses are also close together, so each bite contains more forage, reducing the effort of grazing.

Whether you raise cattle or bison, harvesting forage and feeding in the winter is expensive.  The cost of winter grazing is generally estimated to be about half of the cost of feeding baled forage.  If you have access to pastures or hayland that could be grazed through the winter, you may be able to reduce your cost of production.  Bison are well adapted to winter grazing.  Good planning and pasture management will ensure that an adequate supply of good quality forage is available to them on winter pastures.