From the Oklahoma Cooperative Extension Service
November 21, 2008
In this issue:
Using Wheat Pasture as a Winter Supplement for Cows and a Creep Feed for Calves
Glenn Selk, OSU Extension Cattle Reproduction Specialist
Mycoplasma Pneumonia Takes the Fun Out of Starting Stockers
Dave Sparks DVM, OSU Extension Area Food Animal Quality and Health Specialist
Glenn Selk, OSU Extension Cattle Reproduction Specialist
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.
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.
Wheat pasture creeps provide yet another alternative use of quality small grain pasture in the cow-calf operation. When dry grass pastures or haying areas are immediately adjacent to wheat pasture, the opportunity becomes available for small grain pasture creep feeding of fall-born calves. Creep gates, placed between the cow pasture and wheat field, will allow calves free access to wheat forage while restricting the cows to their dry pasture wintering area. Compared to dry wintered calves, nursing calves allowed access to quality forage of this type can improve their daily gain by .5 to .75 pounds per day.
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. 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.
Cows grazing lush small grain pastures should be fed mineral mixes containing both calcium and magnesium.
Dave Sparks, DVM, OSU Extension Area Food Animal Quality and Health Specialist
Over the past several years pneumonia in stocker calves due to infection with Mycoplasma bovis has become much more apparent. It is hard to say if the prevalence is increasing, or if cattlemen are recognizing it more, but it is demanding more attention. Mycoplasma bovis is commonly found in the upper respiratory tracts of healthy calves, where it does no damage. The problems start when it gains entry to the lungs, especially stressed lungs. The normal course of events is that stressed cattle develop typical Bovine Respiratory Disease Complex, (shipping fever) caused by a bacterial infection, often Mannheimia, Pastuerella, or Hemophilus which follows one of the respiratory viruses such as IBR (Infectious Bovine Rhinotracheitis), BVD (Bovine Viral Diarrhea), PI3 (Parainfluenza), or BRSV (Bovine Respiratory Syncitial Virus). This pneumonia is usually unresponsive to antibiotic therapy and sets up the conditions in the lung for Mycoplasma bovis to become established in the lung and destroy tissue. Thus, Mycoplasma is usually a tertiary invader. In addition to the lung involvement Mycoplasma can cause several other syndromes, especially lameness evidenced by swollen and painful joints.
There is a typical progression to the disease. Two weeks after arrival calves are pulled for treatment of pneumonia but show no response even after treatment with multiple antibiotics. Appetite often remains good, but calves show a depressed attitude and a clear serous nasal discharge. Three weeks after arrival, calves are being pulled for arthritis, with affected calves exhibiting swelling in the knee, elbow, or fetlock. Most death loss occurs between three and six weeks of age. A mycoplasma diagnosis is not usually made until a postmortem is performed.
Treatment of mycoplasma pneumonia is difficult, because most antibiotics are of no value. Some commonly used antibiotics are not effective because they act by destroying the cell wall of the organism and Mycoplasma sp. does not have a normal cell wall. Draxxin® is the only antibiotic approved for treatment of mycoplasma pneumonia. Other antibiotics may help with the other components of mixed infections. Be sure to check with your local veterinarian for treatment recommendations. The two most important factors in the treatment of the disease are early recognition and prolonged treatment. If you do not provide therapeutic levels continuously for 10 to 14 days, the disease will relapse in up to 70% of the cases. It is not effective to attempt to treat the lameness. If you keep these calves near feed and water and encourage them to get up to eat and drink regularly the swelling will subside and most will return to normal. It usually takes several months, however, to get back to a positive gain situation.
Prevention of the disease consists of controlling the initial stressors. An appropriate vaccination program for Bovine Respiratory Disease, good nutrition, mineral supplementation, and avoidance of high risk cattle are all important. Drenching and balling guns spread the organisms between calves, so sterilization of these instruments between uses will help to limit outbreaks. Vaccines currently available against Mycoplasma bovis have not been shown to be effective in beef cattle.
Death losses can easily run twice as high as in other respiratory disease.
If you think you may be having respiratory disease complicated by Mycoplasma bovis in newly arrived stocker cattle, be sure to involve your local veterinarian. Early detection and necropsy diagnosis might very well dictate the color of ink you find yourself using this season.
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