Steve Wikse, professor of large animal clinical sciences, College of Veterinary Medicine at Texas A&M University, answers this month's beef cattle health question.
Q - A friend north of my ranch recently had a cow die from acorn poisoning. I have a lot of woods on my ranch and I've noticed that this year there are more acorns on the ground than usual. I was wondering what the signs of acorn poisoning are in cattle and how could I prevent the disease?
A - The above-average rainfall of last spring and summer has resulted in a bumper crop of acorns this fall in many areas of Texas. Acorns are highly palatable to cattle and are nutritious. In fact, acorns were a dietary staple of American Indians and early settlers who consumed them after they were ground and soaked in water to leach out toxic chemicals. Cattle can consume a substantial amount of acorns without deleterious effects, but can become ill when acorns become more than 50 percent of their diet. This usually happens when forage is scarce and acorns are abundant.
Some cattle, however , develop a craving for acorns and consume enough to lead to poisoning even when forage is adequate. Green acorns are more palatable and contain higher concentrations of tannins, however mature acorns are also toxic. In the spring, cattle can get oak toxicosis by ingesting buds and early leaf growth. Tannins, the toxic chemicals in oak leaves and acorns, damage the kidney, liver and digestive tract. Historically, tannins have been used to "tan" animal hides into leather.
Usually a week or longer after cows or calves load up on acorns they stop eating and stand around with their heads lowered. Breathing becomes rapid and infectious bovine respiratory disease may be suspected when weaned calves have acorn poisoning, but rectal temperatures will be normal or below normal. Initially constipation is observed. Later, many develop a dark, sometimes bloody diarrhea, become dehydrated and are unable to stand. Swellings due to edema develop between the jaws, in the brisket and along the belly.
Young heifer calves may develop greatly enlarged vulvas due to edema. The hallmark of acorn toxicity is severe damage to renal tubules resulting in kidney failure, which accounts for many of the clinical signs. Some affected animals urinate frequently.
Death results in one-to-12 days after initial signs, although some cattle are found dead with no previous signs and others develop a protracted debilitating disease lasting weeks. Calves weighing from 250 to 600 pounds are especially susceptible to acorn poisoning. Nearly all affected cows or calves die if not treated. Animals treated at the start of the illness can sometimes be saved by intravenous fluids to promote kidney function and urination.
The major factor in survival of affected animals is extent of kidney damage.
Thus, survival depends more on the amount of acorns eaten than on treatment.
Daily supplementation with a few pounds of cubes or alfalfa hay may lessen the interest of the cattle in acorns and has been shown to minimize losses in outbreaks of oak toxicosis. The surest way to prevent poisoning is to fence off wooded areas.
Research at Texas A&M University in the early 1960's demonstrated that supplements containing calcium hydroxide would prevent acorn toxicosis. The calcium binds to tannins in the rumen and prevents them from being absorbed into the blood.
Dr. John Reagor, head of toxicology at the Texas Veterinary Medical Diagnostic Laboratory, has given me the following formula for the supplement they recommend fed to cattle to reduce the likelihood of acorn toxicity:
• 50 percent alfalfa hay
• 35 percent cottonseed meal
• 10 percent hydrated lime
• 5 to 10 percent fat
The above supplement is made up as a pellet by the feed mill and must be fed at a rate of four pounds per head every day. It's of critical importance that no grain is fed with this supplement. Grain will make rumen contents more acidic, and binding of calcium to the tannins will only take place in an alkaline environment.
Share this story:
Google
Yahoo
digg
del.icio.us
facebook
Slashdot
