32. COMMON COCKLEBUR

Xanthium strumarium

(daisy family)

TOXICITY RATING: High.

ANIMALS AFFECTED: All animals may be affected. Cattle, swine, sheep, and poultry are more at risk than horses and pets.

DANGEROUS PARTS OF PLANT: The seeds and seedlings contain the highest quantity of toxin, yet the whole plant can be considered toxic. The seed burs can cause mechanical damage.

CLASS OF SIGNS: Gastrointestinal irritation, weakness, breathing difficulty, behavioral changes, cardiac abnormalities, death.

PLANT DESCRIPTION: The angled, sometimes red- or black-spotted stems of cocklebur grow 1 to 3 feet high. Leaves of this many-branched annual are alternate, hairy, rough-textured (sandpaper-like), somewhat heart-shaped, toothed, and lobed (fig. 32). Flowers are inconspicuous with male flowers in terminal spikes, female flowers in clusters in the leaf axils. The fruit is a hard, oval, prickly bur about 3/4 inch long containing two seeds (fig. 32A). Because seeds germinate best after being soaked in water, the plants are usually found along the shores of ponds where water has receded. The edges of farm ponds may be lush with young cockleburs. Seedlings have small strap-shaped leaves 1/4 inch wide by 11/4 inches long (fig. 32B). They also pop up in gardens, fields, roadsides, and other areas of nearly full sunlight.

SIGNS: There are several types of toxins in cocklebur, one being a glycoside, carboxyatractyloside, which causes hypoglycemia (low blood sugar) and a group of sesquiterpene lactones which can cause vomiting (in those species capable of vomiting), weakness, tremors, weak pulse, a loss of appetite and convulsions. Liver damage may also result from these toxins, and death is likely if a sufficient dose was consumed (ingestion of green plant at approximately 0.75% of body weight). The seed bur can cause mechanical damage (please refer to the section on Foxtail barley). The most common time for toxic signs is late spring and early summer for the seedlings, later in the summer for the burs, and at any time seed-contaminated prepared feeds are ingested. As the cocklebur plant matures, the toxicity decreases (except for the seeds). The seedlings are extremely dangerous, and typically sprout in wet areas, such as alongside streams, at the edges of ponds, in receding floodplains, etc. Animals will tend to avoid cocklebur, even the seedlings, as long as there is sufficient forage available. Species that are less discriminant eaters (cattle, swine) are particularly at risk where cocklebur grows. Once toxic signs develop, death may follow within 48 hours. Some animals may recover, but this may take some time (weeks).

Other conditions of toxicity can occur when seeds are incorporated into prepared feeds. Feeds that may become contaminated include hay (especially if cut later in the growing season when cocklebur has gone to seed), silage, or grains (corn, beans). If the feeds (especially the grains) are highly processed, it may be difficult to arrive at an accurate diagnosis of cocklebur toxicosis. The seed is highly toxic, and any species may become poisoned upon consumption.

FIRST AID: If animals are observed eating cocklebur, contact a veterinarian immediately. In the meantime, prevent further consumption of the plant by all animals. Keep animals quiet until the veterinarian arrives.

SAFETY IN PREPARED FEEDS: The seedling, when dried, retains its toxicity, therefore feeds with dried seedlings are not safe for consumption. Mature plants are less toxic, but consumption is still not advised. Feeds that contain burs and/or seeds are a mechanical threat as well as a toxic one, therefore these feeds are also not safe for consumption at any dosage.

PREVENTION: Pasture management is essential to prevent poisonings by cocklebur. Mature, seed-bearing plants should be removed from the pasture to prevent seeding and germination. This is particularly important if the pasture contains any wet areas that are subject to seasonal drying. If removal of the plants is impractical, fence off areas where seedlings are likely to germinate and/or provide for supplemental feed to decrease interest in the seedlings. For prepared feeds, exert extra caution when harvesting for hay, silage, or grains and do not allow any cocklebur to be included. Buy prepared feeds only from reputable dealers.