Winter Grazing & Supplementation
By Dusty Hepper
Ranch Manager, Bad River Ranches – Fort Pierre, SD
The Bison Advantage
Bison have several advantages over beef cattle as it pertains to winter grazing. Like other wild ungulates (elk and deer) bison change their metabolism throughout the year to match forage quality and availability. This is an energy saving mechanism that makes them hardy and efficient in winter grazing compared to cattle. Bison increase their forage intake beginning in the spring when their metabolism is anabolic (high or fast rate of metabolism and rumen turnover) which results in increased body condition or building of body fat reserves through the summer and fall. As winter sets in (November through March), their metabolism slows down as they become catabolic (low or slow rate of metabolism and rumen turnover). During the winter they rely on their fat reserves as a source of energy. Early in the spring, bison will take advantage of the high-quality new forage growth by drastically speeding up their metabolism (they become anabolic), increasing forage intake in order to rebuild body condition quickly prior to calving.
Bison are very well suited to comfortably withstand the harsh winter conditions including sub-zero temperatures, because they have a very dense winter coat. Studies have shown that bison hair is four times as dense per sq./in. as the hair on Hereford cattle. Their thermal efficiency in the winter is second only to a yak. The skeletal and muscular structure that forms their hump allowing mature animals to use their head as a snow shovel, sweeping the snow away to expose the available forage that is often buried during the winter months. We capitalize on these “bison advantages” on Turner Ranches.
Breeding Herds
On “normal years” our mature breeding herds graze standing forage year-round which allows us to greatly reduce our supplement input costs, increasing profitability. Additionally, to achieve optimum economic return we select for bison that fit their environment, instead of artificially changing the environment (extreme winter feeding and supplementing) which allows substandard bison to remain in the herd. If mature bison cows are unable to graze un-supplemented during the winter, calve and then rebreed, they do not belong in our herd. We do not create an “artificial environment” by heavily supplementing our breeding herds during the winter in normal conditions.
However, in cases of drought or severe weather storms, we will assess body condition and may choose to supplement protein for a short time in order to help hold body condition at a minimal level through severe events. Our bison cows normally experience significant weight loss over winter, which is normal if they are in good body condition in the fall. We have measured natural body weight drops in our herds of greater than 100 pounds over the course of a normal winter. We have determined this type of weight loss is expected and normal. You could spend a lot of money and effort trying to avoid this natural occurrence, but we choose not to. We have learned that they will gain weight back quickly in the spring (compensatory gain) when they get on green grass, with no negative effects on performance. This management is always predicated on having ample amounts of forage available for grazing.
Weaned Calves/Yearling Herds
After weaning calves from the cow herd, feeding or supplementation of calves is important to get through weaning stress while continuing to grow frame. All Turner Ranches vary slightly in their weaning timing and supplementation program for their calves. This diversity of weaning management techniques allows us to learn from each other collectively as we strive to find the ideal management and supplement techniques for getting weaned calves through the winter and back on green grass in various regions of the country.
Bad River Ranches calves are weaned in November through December. They are fed grass hay and protein cake seven days a week for up to 120 days after weaning. This is the only period that we supplement protein regularly to any of our bison. Our calves can take advantage of the added nutrition since their metabolism is still anabolic, as the ability to become catabolic only occurs after reaching sexual maturity at age two or older. During this weaning period, we are training our calves to respond calmly to our presence and to follow the cake truck which we will be using as the leader for most pasture moves throughout the course of their entire lifetime on the ranch.
No matter what time of year you are weaning, fall, late winter, or early spring, protein supplementation for sub-adult bison on poor quality pasture or grass hay will provide excellent economic returns as keeping weaned calves growing body frame during the winter helps them excel on green pasture next spring. As green growing forage is high in protein, we discontinue all protein supplementation and run the calves strictly on grass until the next fall when we bring them in and work them. This is the time that we select our replacement bulls and place the remainder of our yearling bulls on feed in our feed yard. The yearling heifers then go back to grass for the winter where they are supplemented in a manner that is very similar to our breeding herds with minimal or no supplementation while they graze winter forage. We place our two-year-old heifers on feed the following spring for finishing in our feed yard.
Protein Supplementation Products
Most Turner Ranches use a cake product that is 22% to 30% crude protein with little energy. We only need to feed 1-2#/hd/day to stimulate rumen microflora growth which increases fiber digestion. Bison recycled nitrogen through their saliva (cattle do not do this) which both aids and adds to the effective protein in the cake. We optimize our supplement program by feeding only what is needed and only at the appropriate time of year.
For many years Turner Ranches fed only grain by-product protein sources which were readily available while being the cheapest alternative. Recently we changed our supplement strategy to use only forage-based protein products (as outlined by the American Grass-fed Association) which will allow our animals to qualify for grass fed markets in the future. We are currently using an alfalfa field pea cake and safflower-based cake as protein supplements in all our herds. Though these plant-based products are incrementally more expensive, use of them allows our animals to “fit under” several grass-fed labels, many of which prohibit any and all grain by-products during the life of the bison. Switching to plant-based protein supplements gives us multiple marketing alternatives down the road.