Spring is getting closer and summer is not far behind. As the seasons change, it’s important to be aware of the different plants that have grown or been added to your surroundings and their potential toxic effects on cattle and horses.
What are some common plants that cause toxicity in cattle and horses?
Cat Barr, PhD, DABT, is the toxicologist for the Texas A&M Veterinary Medical Diagnostic Laboratory(TVMDL). Each year, she works with animal owners from across Texas who need assistance identifying potentially toxic plants.
Although Texas offers a variety of plant life, there are several common plants that grow across different regions of the state.
For example, cocklebur seedlings (Xanthium strumarium) grow statewide and should be a concern for cattle owners.
“Seedings typically sprout around the edges of receding rain puddles,” Barr said. “They are extremely toxic at the four-leaf stage and can cause massive liver damage and rapid death when consumed. Cattle have been found dead within one hundred yards of a plant.”
Another plant of concern is singletary pea (Lathyrus hirsutus). Also called Austrian winter pea, singletary pea is mostly found in north central, northeastern, and eastern Texas. Although the vegetation of the plant is not toxic, the seeds contain toxic amino acids. Singletary pea’s seeds are of most concern for horse owners. Horses tend to be the most sensitive species and experience neurological issues, such as stringhalt gait, once seeds are ingested.
Situational plant toxicosis
In addition to the plants that commonly grow in Texas, Barr also warns of certain situations that may cause plants to become toxic or more available to animals.
High winds during the spring and early summer can result in fallen tree branches. Depending on the type of tree, fallen branches can grant animals easier access to the leaves that may be toxic.
Maple trees (Acer sp.) with wilting or dead leaves are known to cause drastic intravascular hemolysis in horses. This condition can result in weakness, ataxia, and renal failure.
Catkins, the flowers on oak trees (Quercus sp.), and the smaller leaves on the tree have high concentrations of tannins.
“The leaves of concern are smaller than a squirrel’s ear,” Barr said.
High tannin intake can cause liver failure in horses, or capillary fragility and renal failure in cattle.
Producers should also be aware of the forages that contain cyanide.
Choke cherry, cherry-laurel trees, and plum thickets (Prunus sp.) have high concentrations of cyanogenic glycoside in their leaves. Crushing the leaves, such as when being consumed, can release cyanide. Rumen microbes break down the cyanogenic glycoside rapidly, making ruminants more sensitive than other species.
Sorghum sp. forages like johnsongrass, sudan, and haygrazer are more frequently encountered causes of potential cyanide poisoning. The cyanogenic glycoside concentration in these grasses is highest when the plants are stressed, such as when they’re rapidly growing or under drought conditions.
Cyanide can cause animals to go into respiratory distress.
“There have been instances of ruminants dying in as little as 15 minutes following ingestion of plant matter containing cyanide,” Barr said. “It’s important producers keep an eye out for fallen branches following storms. Certain tree leaves can have disastrous effects on cattle.”
How can TVMDL help?
TVMDL’s analytical chemistry section offers several tests and services livestock producers and veterinarians may find beneficial.
One of the most frequently requested services is plant identification. This service allows producers or veterinarians to submit plants to the laboratory for identification and to determine its toxicity, if any. Clients have the option of mailing the plant to TVMDL or for a more convenient method, submitting photos of the plant via email or the TVMDL Mobile app.
In addition to identification services, TVMDL performs tests on feed, rumen contents, GI contents, and forages to determine toxicity levels.
Those interested in these services are encouraged to set up a consultation with one of TVMDL’s veterinary diagnosticians to determine the most practical diagnostic testing route and to create a TVMDL client account.
For more information on TVMDL, visit tvmdl.tamu.edu or call the College Station laboratory at 1.888.646.5623.