We know there are many of you who enjoy the cooler temperatures of fall. While humans average temperature of choice is 72 F, cattle’s average choice is 50 F but the comfort zone is much wider for cattle. So all livestock in the fields and pastures enjoy the annual escape from the oppressive summer heat.
But with the cooling of the season, there are a few dangers for our pasture animals that need to be avoided. This is especially true this year with the fall drought we had this year. Normally we would still have some grass available for grazing but not this year.
If hay is not put out in a timely manner, animals will eat plants and seeds they normally do not touch or eat, especially in larger quantities. For cattle, acorns are in this group. Acorns are plentiful in Catawba County this year. While this is good for wildlife and certain livestock, the possibility exists for cattle to over-consume acorns where cattle are grazed in pastures that may contain oak timber.
Most species of North American oak trees are considered toxic. If these whole acorns are overconsumed, they have the potential for fatal poisoning. The toxic compound in acorns is related to tannic acid.
One mystery is why cattle can be poisoned while hogs, deer, and squirrels are not. When you observe the hog, deer, or squirrel eating acorns, they seem to shell acorns, and because the toxin is concentrated in the shell, this may explain their resistance to poisoning. They may also learn (or maybe naturally select) to not eat too many acorns.
Typically, for cattle, acorns are not a favorite food. If they have plenty of pasture to graze, acorn toxicity is usually not a problem. However, with the drought in early fall, grass is sparse and once they start eating, some cows will gorge themselves on them.
Also some cattle can apparently eat acorns with no ill effect, while others develop kidney and digestive problems that can lead to death. Generally, cows and large calves will be directly affected, but baby calves also appear to be affected through the milk and possibly before birth.
Brood cows consuming acorns during the second trimester of pregnancy have the chance of malformed calves. Acorns can also shutdown milk production (agalactia) in fall calving cows. Affected cattle will first show signs of constipation, followed by an abnormally (dark or yellowish) colored thick diarrhea, sometimes with blood. Clinical signs of illness occur several days after consumption of large quantities of acorns in the fall. Most cattle that have the advanced gastrointestinal problems will lose condition rapidly, and have a gaunt, rough, “humped up” appearance with a diarrhea stained tail and rump.
In mild cases, gastrointestinal distress may be the only result, and the affected animals will sometimes recover. In severe cases, kidney damage (tubular necrosis) occurs, and animals can die within several days.
The best way to prevent acorn poisoning is to keep cattle away from acorns. If pastures contain a substantial number of oaks, the trees should either be removed or cattle fenced out, but if you fence off an area covered with acorns, you may have to leave the fence up for a while.
Acorns retain high levels of tannic acid for several months. An alternative would be to set up a management program that will keep cattle off those pastures from the time acorns start to fall, through Christmas. There is also a grain/protein based supplement containing 10% calcium hydroxide (hydrated lime) that has helped in some situations, but not in others, and probably should not be an alternative to designing a program to keep cattle from eating acorns.