The sight of cattle feeding on green oak leaves or acorns should be a warning sign for producers, signaling not only a potential threat to an animal’s health, but also a reminder to practice better pasture and feed management.
Oklahoma recently was hit hard with freezing rain that brought down many tree limbs across the state; in some areas, that included oaks in cattle pastures, said Brad Secraw, Cleveland County Extension agricultural educator.
“In the Southern Plains states, tannic acid poisoning in cattle that consume too many green oak leaves or acorns is not a frequently raised issue, mainly because the livestock don’t find them all that palatable and will generally only eat them if other resources are not available,” he said. “The problem can be largely avoided by ensuring cattle have access to good grazing and supplemental feed.”
Studies show livestock are more likely to consume green leaves as opposed to dried leaves. Most livestock are susceptible to tannic acid toxicity, but cattle and sheep are most often affected. Clinical signs of illness typically do not appear until several days after gorging. Producers who notice downed oak tree limbs in pastures where cattle exhibit severe depression, lack of appetite, emaciation, serious nasal discharge and constipation followed by diarrhea need to contact a veterinarian immediately.
“Calcium hydroxide comprising 10% of the ration may be used as a preventive measure if exposure to downed oak limbs with green leaves or acorns cannot be avoided, but the timing must be just right,” Lalman said. “A better option is to keep a watchful eye out and provide sufficient amounts of hay if adequate grazing resources are not available, thereby reducing the likelihood of cattle wanting to eat oak leaves or acorns.”
Calves and yearlings seem to be affected more often than mature cattle. An adult would have to consume more acorns or leaves to receive the same level of toxicity as a young animal.
Oklahoma is typically the nation’s fourth- or fifth-leading producer of cattle annually, according to National Agricultural Statistics Service data.