No oak on the alternative feed list

Nov 18, 2011

As county after county continues to be added to the 2011 drought map, the total cost to agriculture is still unknown, but the devastation has been obvious with shortage of feed and water, total loss of crops, downsizing cattle herds, and fire destruction. But other less obvious, droughtrelated problems will continue to increase over the winter months.

One concern producers in some areas face is oak toxicity. During drought conditions, oak trees respond by producing more acorns. While cattle eating acorns or oak is not an everyday problem, it can be catastrophic if they do.

Northern California saw an outbreak of oak toxicity several years ago, with over 2,700 losses from the rare disease.

Last spring, four cows were reported dead in California’s Tulare County foothills. The cows were grazing in an area with a heavy crop of acorns. These cattle were not available for necropsy and cause of death was not confirmed, however, acorn toxicity was suspected.

“Acorn toxicity can hit at anytime, under the right circumstances.”

California reported higher than normal production of acorns for 2011, and in some areas, the highest production years observed.

There are about 500 species of oak across the Northern Hemisphere. Their habitat ranges from dry rocky slopes to wet bottomland to heavy sands, according to Texas A&M University (TAMU) AgriLife Extension. Most species are specific to a certain habitat type.

The toxins in oak are complex compounds called gallotannins. These compounds are toxic to cattle, sheep, goats, horses and dogs. The poison can be found in the buds, flowers, young stems and acorns, but mature leaves are not toxic. Poisoning can occur in the spring, when cattle eat young leaves, buds, stems and/or flowers. Poisoning from large oak trees is most often the result of livestock consuming a large amount of acorns in the fall and early winter.

However, there are cases each year in which cattle consume the young leaves from tall trees blown down during a wind or hailstorm. As little as 6 percent of an animal’s body weight of dry plant material may be enough to cause oak poisoning, according to TA- MU’s website.

One of the biggest risks is scarce forage, and lots of acorns on the ground. With high winds, hailstorms and snowstorms, outbreaks in some areas are worse in late winter and early spring when oak trees are budding. Wet snowstorms break branches and cover available grass, sending cattle looking for alternatives. The tender leaves and buds become the available forage, increasing the risk of toxicity.

According to a report from John Mass, DVM, University of California, Davis, California has more than 50 common species of oak trees and all of them contain some level of the chemicals that can cause problems in cattle. According to Mass, the gastrointestinal tract (mouth, esophagus, rumen and intestines) is damaged by direct contact with the toxins, resulting in ulcers, bleeding, and perforation, in some cases.

Symptoms usually appear shortly after cattle eat 50 percent or more of their diet as oak (leaves, buds, acorns). Some animals may simply be found dead. Others may appear weak and listless, without an appetite. Bloody or dark diarrhea may be noticed one to two days after a cow over indulges on the toxins. As kidney failure progresses, fluid may accumulate around the anus or vulva. Throughout, the cattle appear weak, listless, and have no appetite.

Recovery for an animal depends on the severity of the toxicity, and is dose related. “It’s a sliding scale,” Mass said.

Acorn calf syndrome is another potential outcome of oak toxicity. Acorn calves are deformed calves born to cows that have ingested large numbers of acorns during the second trimester of pregnancy. The poor nutrition and exposure to acorns causes calves to have short legs, abnormal hooves, and misshapen heads, according to Mass.

“Oak toxicity can be prevented by supplementing the cattle with hay when forage conditions are poor and acorns are abundant. Likewise, when late snowstorms cover the forage and knock down oak limbs with large amounts of buds and young leaves, be sure to start hay supplementation immediately,” Mass said. A delay of only a day or two could result in many deaths. Prevention of acorn calves is also a matter of being sure adequate forage is available or supplementing with hay or other forage when running the cattle in oak areas.

“We consider it a problem of opportunity,” Mass said. Acorn toxicity can hit at anytime, under the right circumstances. — Traci Eatherton, WLJ Editor