Is stockpiled pasture really of sufficient quality to carry cattle all through the winter? This question has a classic, “it depends” answer.
Let's start with several different “it depends” factors. What kind of forage is it? How was it stockpiled? What class of cattle are we talking about? What will the grazing management be? All these will help determine the answer.
Stockpiled cool-season forages are typically adequate in protein for most classes of livestock but may be deficient in digestible energy. Warm-season forages, on the other hand, tend to be protein deficient, but may have adequate energy if the rumen can capture it.
During my time with the University of Missouri (MU), we conducted numerous studies with stockpiled pastures; tall fescue was our most common winter forage. A properly grown fescue stockpile might start the winter at 16-18% crude protein (CP) and 65-70% total digestible nutrients (TDN), and end the winter with 10-12% CP and 50-55% TDN, depending on weather conditions.
Stockpiled bermudagrass might start the winter with 12-14% CP and end the winter at less than 8%, with starting TDN at 55-60% and ending TDN less than 50%. Other cool- or warm-season forage mixtures generally run below these benchmark levels. Native warm-season range is generally lower in CP than bermudagrass but may have comparable energy content.
How and when the stockpile is grown has a major bearing on its nutritive value. We generally recommend a 60- to 75-day stockpiling period with cool-season forages; any longer results in lower quality at the beginning of winter. For bermudagrass and other non-native warm-season grasses, 45-60 days is appropriate. Any longer won't provide you more yield, it just lowers quality.
Fertilizing with nitrogen at the start of the stockpiling period will produce higher CP levels and may raise digestibility.
Stockpiled pasture with legumes in the mix is generally higher quality at the outset of winter but deteriorates more rapidly.
A dry, pregnant beef cow has a 7-8% protein requirement and a TDN requirement around 53%. Based on the above ranges, cool-season stockpiled pasture should provide adequate quality for dry, pregnant females all winter without supplementation, providing quality deterioration due to weather isn't excessive.
Stockpiled bermudagrass may have adequate protein and energy levels at the beginning of winter, but supplementation likely will be needed by early- to mid-winter. A protein supplement likely will give the greatest benefit on stockpiled warm-season grasses. Protein supplementation of stockpiled native range is usually needed from the onset of winter.
Fall-calving cows change the equation dramatically. The higher protein and energy demands of lactation can quickly exceed what stockpiled pasture can provide, unless topnotch pasture and grazing management is employed. The best-case scenario is using a properly grown fescue-based stockpile.
During my last two winters at MU, we took fall-calving cows in the first year from Nov. 14 to March 19, and in the second year from Nov. 14 to March 28, with no supplementation. Cows came out of winter with body condition scores greater than 6, bred at 93% in a 45-day season, and had calves gaining in excess of 2.25 lbs./day, all on stockpiled pasture (no creep-feed). Fall-calving cows on warm-season stockpile may require substantial supplementation to maintain condition and rebreed efficiently.
What about stockers or replacement heifers? Basically the same principles that apply to fall-calving cows apply to growing stock. One way to get the optimal use of stockpiled pastures in a cow and yearling operation is to top-graze with the yearlings and clean up with the cows.
As long as yearlings aren't asked to take off any more than the top 25% of the stockpile, they can do reasonably well for a good part of winter. Appropriate supplementation can really boost their performance on winter dormant pasture.
How the pasture is grazed makes a big difference in how long adequate nutrition remains in the pasture. If the whole herd is just turned out on the entire pasture, quality forage disappears quickly. Strip grazing forces them to take the best with the worst, leaving higher quality forage available much later in the winter.
So the overall answer is stockpiled pasture can provide adequate nutrition throughout the winter. But you need to know how to manage it from the time you start letting it grow until the cow takes her last bite before spring.
Jim Gerrish is a grazing management consultant based in May, ID, and former lead pasture researcher at the University of Missouri's Forage Systems Research Center in Linneus. He can reached at 208/876-4067, firstname.lastname@example.org, or visit http://americangrazinglands.com.