Several years ago, I worked with some farmers who had cattle to die with quercus poisoning. In laymen's terms, quercus poisoning occurs when cattle consume oak buds or acorns. Most animals are susceptible, although cattle and sheep are the species that are most often affected. Most species of oak in our area are considered toxic in this respect. The term quercus comes from the scientific or botanical name for oak.
In pastures where grass is short, cattle producers need to be aware of the potential problem for quercus poisoning. Cattle located in areas of short forage supply may be tempted to eat green acorns. A little forethought in this respect could prevent a lot of tragedy later.
Consumption of large quantities of young oak leaves in the spring or green acorns in the fall produces clinical signs several days later. Signs include lack of appetite, depression, emaciation, serious nasal discharge and constipation followed by mucoid to hemorrhagic diarrhea. The toxins can cause kidney damage which may not be apparent at present but could lead to serious health problems later.
Kidney damage caused by quercus poisoning is irreversible. Since this effect of the poisoning is not noticeable until it's too late, cattlemen should take preventative measures for any cattle in the area should an outbreak of quercus poisoning occur. In some cases, this could mean fencing cattle out of areas where they have been observed eating acorns. The cost of fencing or the lack of other grazing areas may force producers to risk their cattle being exposed to quercus poisoning.
Calcium hydroxide comprising 10 percent of the ration may be used as a preventive measure if exposure to acorns cannot be avoided. This may be a feasible alternative for dairymen who have cattle on a controlled diet but is impossible for beef cattle producers who have no control over the animal's diet in a pasture situation.
Calves and yearlings seem to be affected more often than mature cattle. This is most likely a function of body size whereas a full grown cow would have to consume more acorns or leaves than a younger, smaller animal to get the same level of toxicity.
One thing that producers can do is be sure that forage is available. If there is not adequate grazing then provide hay. Cattle who don't have adequate forage or hay will be tempted to eat the acorns where they are available. This is expecially true after the frost has killed the grass. I suppose green acorns taste better than dead grass.
Fortunately, green acorns and leaves are the most toxic. As acorns cure after falling, they will become less toxic as a function of time requiring animals to eat more to get the same level of toxicity. Cured acorns should also be less desirable to animals than green acorns.
Even though this problem will diminish with time it is not going to go away overnight. Depending on what other foods are available, it could be as long as two months before the danger has passed. In the meantime, let's hope the winter grazing jumps up soon or the hay is real tasty this year.