As a result, the cyanide ion inhibits the release of oxygen from the hemoglobin of blood to individual cells. Without oxygen, cellular respiration ceases and cells die rapidly due to hypoxia. Signs of prussic acid poisoning can occur within 15 or 20 minutes to a few hours after animals consume potentially toxic forage. Excitement, rapid pulse rate, and generalized muscle tremors occur initially, followed by rapid and labored breathing, staggering, and collapse. Foaming at the mouth, excessive tearing, and voiding of urine and feces may occur.
Animals often lie prostrate and have muscle spasms and convulsions.
Mucous membranes are usually bright and pink, and blood will be a characteristic bright cherry red. Treatment must be administered quickly because death can occur within minutes during severe convulsions. Incoordination of the rear legs, lack of urinary control, and paralysis and inflammation of the bladder can occur. The unidentified toxic principle causes spinal cord lesions. Pregnant mares may abort, and surviving foals may have musculoskeletal deformities.