Spring diseases in fall
—Recent rains are encouraging producers, but also causing animal disease concerns.
As fall approaches, cattlemen in nearly all geographical tiers are experiencing some relief from scorching temperatures and lack of rainfall. Recently, producers have received late rains that are giving them hope for additional grass growth, as well as wheat for those who plan to stock cattle for fall and winter grazing. Although the rain is needed, it is also causing producers problems they usually don’t experience in late summer and early fall, but rather the spring. More specifically, along with new grass growth, producers are seeing an increasingly higher occurrence of grass tetany and metabolic pneumonia.
Grass tetany is more widespread and more familiar to cattle producers. Grass tetany occurs when there is a low level of magnesium in the cow’s blood. Grass tetany is caused by a low content or availability of magnesium found in hay or pasture forage, according to Edward Rayburn, extension forage agronomist for West Virginia University.
“The availability of magnesium is reduced if the forage is high in nitrogen or potassium,” said Rayburn. “This often occurs after heavy application of chemical fertilizers or manure. Unfortunately, producers who practice good pasture and forage management may experience grass tetany more frequently than farmers who do not fertilize or use improved management methods.”
In addition to fertilizing pastures, another factor that may increase the occurrence of grass tetany is rapidly growing grass, which is currently happening due to the recent rains. Fast growing grass often contains inadequate amounts of magnesium for cattle, according to Russ Daly, South Dakota State University extension veterinarian, who said that is the source of the concern for producers in South Dakota.
At this point, Rayburn said there is very little cattlemen can do to completely prevent grass tetany. He said the most important thing to do is watch cattle carefully, looking for signs and symptoms of the disease, and respond immediately with treatment.
The symptoms of grass tetany closely resemble those of milk fever or ketosis. These include nervousness, lack of coordination, muscular spasms, staggering and death. When the disease is suspected, a veterinarian should be called immediately to diagnose and to initiate treatment, said Rayburn. However, in beef cattle operations, cattlemen do not always have the opportunity to observe the signs of the disease and affected cattle may be found dead in the pasture.
Daly said grass tetany often progresses so rapidly the symptoms are not observed, and the problem is not identified until the animal is down or dead. He said once the disease presents itself, the treatment is intravenous solutions of magnesium and calcium. However, this is best, according to Daly, if given as soon as symptoms occur. Once the animal is down, it may be too late. If done earlier, prevention is the best remedy. To prevent the cow-killing disease, Rayburn recommends having soil sampled and treat the soil as recommended.
“It is highly recommended that regular forage samples are obtained for analysis,” said Rayburn. “This simple procedure will provide valuable information for mineral supplementation to optimize livestock nutrition and production.”
He said if the tests show a pasture has soil that is low in magnesium, do not apply heavy rates of nitrogen, potash or manure in early spring. Instead, make fall or late spring applications. The best medicine for now, according to Rayburn, is to choose a good mineral supplement high in magnesium.
“To prevent grass tetany, provide adequate magnesium in a herd’s mineral supplement,” Rayburn said.
A less common, but still problematic disease usually found in the spring, but with recent weather conditions is becoming present now, is metabolic pneumonia.
This disease attacks the respiratory system. Daly said it is an acute respiratory disease that occurs very rapidly. He said lush green pastures often contain very high levels of amino acids which, when in an animal’s stomach, are converted into a substance that leads to toxicity in the lungs.
Daly said the signs and symptoms include difficulty breathing, breathing with the mouth open, salivation and standing still with necks extended outward. In addition, he said animals may go down under sudden stress.
The downside to metabolic pneumonia is there is no guaranteed treatment once the disease is identified. The best process is prevention. The best way to do that, according to Daly, is limit the accessibility to lush pastures and supplement with feed additives, best prescribed by your local veterinarian.
Daly said the best way to prevent both diseases is to wait until the grass regrowth has slowed down before turning the cattle back into the pasture.
Rain is undoubtedly a good thing, giving optimism to cattle producers who were seriously considering large herd reductions and even selling out completely. The rains will allow wheat to grow, supporting stockers, as well as limit the amount of hay that will need to be fed this winter. However, industry leaders are simply issuing a warrant of caution to cattle producers. Be aware of the occurrence of these diseases; know what to watch for and consult local veterinarians for advice for prevention, including what additives and mineral supplements should be fed now, to prevent significant losses to the bottom line. — Mike Deering, WLJ Editor