COW/CALF CORNER – Assuming more fall rainfall comes to the Southern Plains, wheat pasture will again be a key source of protein and some energy for many cow herds in this part of the United States. If that rainfall occurs, grazing of wheat usually will start in late November or early December.
Limited grazing of wheat pasture has proven to be the best and also more efficient approach for utilizing this high-quality forage with mature beef cows. 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 or hay for 2 – 3 days. A pattern of one day on wheat and 1 day off, should meet the protein needs of the same cow after calving. Producers must be reminded that adequate forage must be available in the dry grass pastures or in the form of hay to provide much of the energy needs of the cows in the “off” days.
The day on wheat pasture should be defined as that amount of time required for the cow to graze her fill of wheat forage (3 – 5 hours) and not a full 24 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. A 3 – 5 hour grazing limit helps to avoid the unnecessary loss of valuable forage due to trampling, bedding down and manure deposits. Under normal weather conditions in the fall, enough wheat forage should be accumulated by early December to supply the protein needs of about 1 to 1.5 cows per acre throughout the winter months when limit grazing is practiced.
Producers who decide to use continuous grazing programs, should watch out for the possibility of “grass tetany.” Grass tetany will normally strike when older cows are grazing small grain pastures in the early spring and the danger will tend to subside as hot weather arrives. A mineral deficient condition primarily due to calcium, and to a lesser degree to magnesium, is thought to be the major factor that triggers the disorder and normally affects older cows that are nursing calves under two to three months of age. Dry cows are seldom affected.
When conditions for occurrence of tetany are suspected, cows should be provided mineral mixes containing 12 to 15 percent magnesium and be consumed at 3 to 4 ounces per day. 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. Because tetany can also occur when calcium is low, calcium supplementation should also be included. Cows grazing lush small grain pastures should be fed mineral mixes containing both calcium and magnesium. If signs of grass tetany are noted, call your local large animal veterinarian immediately. Symptoms of tetany from deficiencies of both minerals are indistinguishable without blood tests and the treatment consists of intravenous injections of calcium and magnesium gluconate, which supplies both minerals.
By Glenn Selk, Oklahoma State University Emeritus Extension Animal Scientist