Wheat pastures are a widely used forage resource in the Southern Plains to maintain beef cattle through winter and spring; however, for most cows, their residence on wheat pastures needs to be restricted to realize the highest grazing and nutritional efficiencies.
“The protein requirements of a dry cow can be met by allowing her to graze on wheat pasture for one day and returning her to dry pasture grass and/or hay for two to three days,” writes Glenn Selk in a recent Cow/Calf Corner newsletter from Oklahoma State University Extension. “A pattern of one day on wheat and one day off should meet the protein needs of the same cow after calving,” adds the emeritus animal scientist.
Selk notes that one day on wheat pasture doesn’t translate to 24 hours. Rather, he defines it as the amount of time required for the cow to graze her fill of wheat forage, which is usually three to five hours.
“This short time on wheat allows the cow to gather adequate amounts of protein to carry her over the ensuing days on dry grass or hay,” Selk explains. “A three- to five-hour grazing limit helps to avoid the unnecessary loss of valuable forage due to trampling, bedding down, and manure deposits.”
If wheat is planted in a timely manner and near normal weather conditions persist, there should be enough wheat forage available by late November or early December to supply the winter protein needs for one to 1.5 cows per acre, assuming limit grazing is practiced.
Selk cautions that grass tetany can be a problem if continuous grazing is used, especially for older cows nursing young calves during early spring. Dry cows rarely suffer from the condition.
“When conditions for the occurrence of tetany are suspected, provide cows a mineral mix containing 12 to 15 percent magnesium and ensure it is consumed at 3 to 4 ounces per day,” Selk recommends. “It is best for the supplements to be started a couple of months ahead of the period of tetany danger so that proper intake can be established.”
Grass tetany can also occur when calcium is low. Symptoms of tetany from magnesium or calcium deficiency are indistinguishable without a blood test.
For cows suspected of suffering with grass tetany, treatment often consists of intravenous injections of calcium and magnesium gluconate, which supplies both minerals.
“Cows grazing lush small grain pastures should be fed mineral mixes containing both calcium and magnesium,” Selk concludes.