Lead poisoning in young horses may cause which skeletal abnormality?

• A. Abortion in cattle
• B. Epiphyseal enlargement in hind limbs
• C. Epiphyseal enlargement in colts
• D. Spinal stenosis

Answer: (C)

Lead interferes with normal endochondral bone formation at the growth plates in young, rapidly growing horses. In foals and colts, the growth plates (epiphyses) are active, and lead disrupts chondrocyte maturation and the cartilage-to-bone transition, often causing the epiphyses to enlarge as bone formation lags behind cartilage growth. This makes epiphyseal enlargement in colts the characteristic skeletal change seen with juvenile lead toxicity.

Abortion in cattle, spinal stenosis, or a location-specific hind-limb enlargement do not fit the typical pattern of lead's effect on the growing skeleton in young horses, so the described epiphyseal enlargement in colts best reflects the known consequence.