Return of rains brings springlike pasture growth

WEST LAFAYETTE, Ind. (WLFI) - Along with cooler fall temperatures, the return of precipitation after an extremely dry, hot summer has caused a springlike regrowth in area pastures that can mean some health risks for grazing cattle.

Lush, green growth in mostly grass pastures can cause cattle to suffer grass tetany, a potentially fatal condition caused by a magnesium deficiency.

Bloat, on the other hand, is more of a concern in heavy-legume pastures.

"Generalities can be dangerous, but grass tetany is classically seen in the spring with older, lactating beef cows on lush, vegetative, grass pastures when nighttime temperatures are below 55 degrees," said Purdue Extension beef specialist Ron Lemenager. "These are the same conditions our fall calving herds are now experiencing, which makes them the most susceptible."

With this summer’s drought, Lemenager says grasses have reduced magnesium uptake from the soil that is aggravated when soil profiles have high amounts of potassium and nitrogen.

Many farmers and ranchers fertilized pastures in the spring, and with the lack of rain, there has been a bit of nitrogen and potassium carryover.

"In addition, magnesium absorption in the animal is compromised when dietary potassium intake is high and sodium intake is low, which is a characteristic of lush, vegetative growth," Lemenager said.

Grass tetany is particularly dangerous because the time from the first symptoms of coma and death in animals can be as few as two or three hours.

Symptoms can include excitable and aggressive behavior, muscle tremors and convulsions.

"Early detection and treatment is extremely important, but the ultimate goal is prevention," Lemenager said. "Producers should provide the cow herd with a vitamin-mineral supplement that is both palatable and contains higher magnesium concentrations – typically about 4 percent."

Bloat is a digestive disorder that happens when gas accumulates in the rumen. Gas production is normal, but when the animal’s ability to release the gases is impaired, pressure builds and the animal gets bloated.

One of the first symptoms is a swollen abdomen. Cattle might also be lethargic or show signs of respiratory distress. Severe cases of bloat can cause death within two to four hours of onset because the swollen rumen prevents normal breathing.

Completely preventing bloat isn't possible, but Lemenager said there are management techniques to lower the risk. They include making sure cattle are full before first allowing them to graze, feeding dry grass hay or corn silage before turning animals out to pasture, delaying turnout until pastures are dry after dew or rain, monitoring animals every couple of hours for the first six to eight hours after turnout, considering anti-bloat supplements (but they need to be included in the diet for at least a week before turnout onto a high legume containing pasture) and carefully selecting which legumes to plant when renovating pastures.

"Death from grass tetany and pasture bloat can occur quickly and it is often too late when producers first observe animals in distress," Lemenager said. "Benjamin Franklin once said an ounce of prevention is worth a pound of cure and that advice fits both grass tetany and pasture bloat. It is much easier and more cost-effective to proactively manage cattle to prevent these ailments than to treat them after they occur."