Cows grazing stockpiled forage this winter may find springtime-quality nutrition locked under the snow.
"Our analysis shows that once grass is frozen, the nutrition is locked in place," said Rob Kallenbach, extension agronomist for the University of Missouri. "The quality of the feed stays fairly stable, as long as the grass remains frozen. Once the grass begins to thaw, the soluble sugar content and the protein content begins to go down.”
He's learned this by clipping winter forage samples from pasture plots for two years. Each sample is analyzed for nutrient content. MU agronomist and animal scientists have long advocated the stockpiling of pastures, particularly tall fescue grass, which is found on most beef farms in the state. The study by Kallenbach and associates measures for the first time on a systematic basis what happens to nutrient content of grasses through the winter months.
"We're finding the quality of the stockpiled grass – now frozen – is much higher than the quality of baled fescue hay put up last summer," says Mr. Kallenbach.
The crude protein content of the stockpiled tall fescue grass remains above 16 percent through the winter, the forage agronomist has found. "That's more than adequate for spring-calving cows," says Mr. Kallenbach. Mature, dry, pregnant cows that go into the winter in good body condition can get by on crude protein of 8 to 9 percent.
ADF (Acid Detergent Fiber) is a chemical test of forage that indicates the energy content. Lower ADF –forage with lower fiber content– indicates a more nutritious feed.
"The ADF on tall fescue runs 30 to 35 percent through February," adds Mr. Kallenbach. "The ADF on the best alfalfa hay is around 28 percent. That is on the best quality dairy alfalfa hay trucked in at great expense."
The ADF on the stockpiled grass being eaten now is lower than the hay, because the cows are getting more leaves and fewer stems. The barren stems preserved in the hay bales increase the fiber content of the ration.
Jim Gerrish, research agronomist at the MU Forage Systems Research Center, says the cowherd at the research farm near Linneus, Mo., kept grazing on stockpiled fescue in spite of the severe winter weather. In cold weather, even with snow covering, they ate the stockpiled grass. Snow doesn't slow the cows that have learned there is good feed hidden under the white covering.
"They just pushed the snow aside and kept on grazing," says Mr. Gerrish. " Having the cows harvest the forage in winter is better than cranking the tractor and hauling baled hay on a zero-degree morning."
Mr. Kallenbach said he has been amazed at how much snow the cows will dig though to get to the frozen grass. "I've seen them go down through 7 or 8 inches of snow. Of course, the taller the grass and the thicker the stand, the more they will work to dig it out. Ice is another matter, the agronomists said. When the snow crusted hard, they went mostly to eating hay.