Four head mature cows have been reported dead in Tulare County foothills from 2500 feet to 1000 foot elevations. All were in the vicinity of Blue Oaks with heavy crop of acorns.
Neil McDougald, Livestock Range Advisor of Madera County indicated that this year is similar to other years he has seen where there have been incidents of acorn toxicity. There is a very large acorn crop, and recent rains has led to some early green-up under Oak Trees which can result in some cows camping and eating an overload of acorns resulting in acorn poisoning.
Most cattle in California spend at least part of the year in areas where oak trees abound. Health problems due to ingestion of oak leaves or acorns are certainly not an everyday problem; however, when problems do occur they can be catastrophic. Several years ago, in a few northern California counties, about 2,700 cattle died due to oak toxicity1.
Some years have much higher production of oak acorns than others and this year, 2011 in the Foothill Ranges of the Southern Sierras, has been reported as one of the highest production years observed. In addition early rains may increase the risk of acorns by reducing the nutrient value of last year’s forage, as well as causing an early greening of grass under the oaks where acorns are accumulating.
During the week of October 10, 2011 four head mature cows were reported to be found dead in Tulare County foothills from 2500 feet to 1000 foot elevations. All were in the immediate vicinity of Blue Oaks with heavy crop of acorns. These cattle were not available for necropsy and cause of death was not confirmed, however oak acorn toxicity is suspected.
Oak toxicity symptoms usually appear when cattle eat 50% or more of their diet as oak (acorns, leaves, buds). Toxicity can be prevented by supplementing cattle with hay or other supplements when forage conditions are poor and acorns are abundant. A higher risk may occur if early or late snowstorms covers available forage and knocks down oak limbs with large amounts of buds and young leaves or acorns, be sure to start hay supplementation immediately. A delay of only a day or two could result in many deaths.
There are two recommendations to avoid cattle loss due to acorn toxicity. One is to provide supplement to draw cattle away from the acorns, so that their exposure decreases. The other is to remove cattle observed eating acorns from fields with high levels of acorns.
It is recommended that producers work with their local veterinarian and/or diagnostic laboratory, to be certain of the actual cause of death in all livestock losses. There are many other factors that can cause sudden death and although oak toxicity may be likely and immediate actions should be taken to prevent further deaths, a follow up with a veterinarian is often the best course of action to prevent further losses. For a more comprehensive discussion on identification and recommended actions for Oak Toxicity and Acorn Calf syndrome in cattle please refer to the link below.
Dr. John Maas, UC Davis Extension Veterinarian, informative article on oak toxicity (OAK TOXICITY UCD Vet Views California Cattleman, Jan 2001):
http://www.vetmed.ucdavis.edu/vetext/INF-BE_cca/INF-BE_cca01/INF-BE_cca0101.html.
Blue Oak Acorn
Cattle Pasture amongst Blue Oaks