Goldenrod, specifically the Rayless Goldenrod, does grow in New Mexico and can be a concern for livestock producers. To achieve toxicity, horses would have to consume around 1 to 1.5% of their body weight in the plant. Lactating mares may also pass the toxin through the milk to the young. The toxin is present both while the plant is growing and while it is dormant. Horses are most likely going to experience poisoning when other forage is not readily available.
Symptoms include weakness, depression, stiffness while walking, trembling in the muscles and nose, constipation and dribbling of urine.