13. CULTIVATED OATS

Avena sativa

(grass family)

TOXICITY RATING: Moderate.

ANIMALS AFFECTED: Cattle, swine, sheep, goats, poultry, horses.

DANGEROUS PARTS OF PLANT: All parts.

CLASS OF SIGNS: Breathing difficulty, skin irritation, paralysis, convulsions, death (rarely).

PLANT DESCRIPTION: This widely cultivated annual grass has escaped into waste places. The plants grow up together in small tufts. The fruiting structure is a terminal, loose panicle (fig. 13).

SIGNS: Oats may cause up to three separate problems, depending upon the conditions:

a) Oats can accumulate excessive amounts of nitrates, especially when heavily fertilized. Many grasses and forages can accumulate toxic levels of nitrates depending upon fertilization practices. This is a serious problem, especially in cattle. The signs are then consistent with nitrate toxicosis: the blood turns a brownish color due to the action of nitrate on hemoglobin. The blood is not capable of carrying oxygen efficiently, and animals show signs of hypoxia: increased respiratory rate, anxiety, collapse, convulsions,and death. Nitrate toxicosis is less often reported in non-ruminants (horses, swine, etc), but can occur. The primary signs in these species is stomach and intestinal irritation, although an inability of the blood to carry oxygen may develop and require treatment.

b) Oats can also induce a photosensitivity reaction in animals, although the exact mechanism (direct contact and/or ingestion) is uncertain. The skin becomes increasingly susceptible to damage by ultraviolet radiation, and the typical presentation in affected animals is sunburn on the lightly pigmented parts of the body. Both fresh oats and oat straw can cause a skin reaction.

c) Moldy oats (called smutty oats), which result from the improper curing or storing of oat hay, can cause paralysis, convulsions or death if sufficient quantities are ingested.

FIRST AID: In all three cases of possible toxicoses, the first and most important step is to remove the oats from the animals.

a) For nitrate toxicosis, it is best to call a veterinarian, especially when cattle or other ruminants are affected. There are emergency measures that can be performed, but severely affected animals still may die. Horses, swine, and poultry are less likely to be affected, but if clinical signs develop, they may require treatment as well, although it may be impractical to attempt treatment on swine or poultry.

b) For photosensitization, allow the animal access to shade. The animal may need shade for a week or two until the sunburned areas heal. Animals on pasture can be turned out at night and stabled during the day. Remove oat straw if used for bedding. The sunburn may be severe enough to prevent normal function, such as seeing, eating, walking, allowing young ones to nurse, etc. In these cases, a veterinarian needs to be called to provide supportive care until the lesions heal. In addition, a veterinarian needs to be called if the sunburned areas are extensive or if they appear infected, or if the animal is depressed and unwilling to eat.

c) For moldy oats, discard affected feed and provide proper forage. If clinical signs develop, call a veterinarian.

SAFETY IN PREPARED FEEDS: Ideally, oat hay with excessive levels of nitrate should not be fed. If feeding this hay cannot be avoided, the animals should receive a well-balanced and adequate diet, since these animal will be less likely to show toxic signs. Nitrate contaminated feed should only make up a small portion of the total ration. Since the cause of oat photosensitivity is unknown, consumption of oat hay or grass may induce the clinical syndrome. Moldy oats are not safe for consumption and should be discarded.

PREVENTION: Ideally, the oat feed should be discarded. If this is impossible, know that properly fed cattle can consume forages higher in nitrate than can poorly fed cattle, therefore, feed cattle an adequate and balanced diet, especially if high nitrate forages are to be included in the diet. Do not over-fertilize oats or any grass forage, to reduce the likelihood of this common toxicosis. Photosensitive individuals may need to have oats permanently removed from their diet. Moldy oats should never be fed.