Michigan State University this week issued a warning to cattle producers using stover as a feedstuff after receiving reports of three cattle found dead following turnout on a 40-acre late-harvested corn field for stover grazing.
The 85-cow herd had been grazing mixed grass pastures through the summer and into early December. The three fatalities were found lying down and "looked as if they had essentially fallen asleep and died," the Extension service said.
The three dead cows were taken to the Michigan State University Diagnostic Center for Population and Animal Health for necropsy. Veterinarians later determined that the cows had died of acute rumen acidosis, also known as grain overload, MSU said.
According to the University, grain overload is most common in cattle that gain access to large quantities of readily digestible carbohydrates, usually grain, with no or limited previous exposure. While the amount of feed needed to produce illness depends on the kind of grain, the animal's exposure and the nutritional status of the animal, MSU said the illness is caused by a rapid change in the microbial population in the rumen.
Ultimately, this change leads to production of large quantities of lactic acid and a chain reaction of other events that result in to cardiovascular collapse, renal failure, muscular weakness, shock and acute death.
MSU said farmers should avoid similar situations by inspecting fields before turnout to ensure there is not excessive whole corn available. The University suggested gradually increasing grazing time as animals become accustomed to grain exposure.
Strip grazing is also an option to reduce the grain exposure and force cattle to eat the whole corn plant (cob, husk, stocks), thus increasing fiber input and decreasing grain intake.
MSU stresses that animals should have plenty of easily available water, and producers may also provide supplemental hay to increase fiber intake.
In the field that the 85-cow herd had been grazing, MSU said there were large areas of corn that had been only knocked down, not harvested.