A horse can colic and die from eating sugar cubes, too much grain, spoiled grain, improperly cured hay, grass clippings and yes even tobacco. They like the taste, they love hemp plants, and acorns (too many acorns. Are toxic to horses)
Ehsterr it is they ate if it causes too much gas they can use their intestines churn, twist and loop around each other therefor killikg the horse if it can’t get into surgery, even with surgery too many horses die from the stress and sjock from the combination of surgery and colic.
If it’s @ny conciliation to you back in the 1800’s farmers used tobacco to deworm their horses but not a whole can, about four cigarettes worth.