Pine (Pinus ponderosa)
Very low toxicity to Horses

Toxic parts and chemical: Isocupressic acid

Symptoms: the resin in pine needles can cause
cattle to abort, but it is rare for horses to be
diagnosed with problems from ingesting them

Pine needle extract is used to make fly sprays
for horses, but is harmless to the horse.
Keeping Your Miniature Horse Healthy
pine tree
Cruz Mountain Miniature Horses- Home Page