In recent months, we have been presented with several cases of rickets in juvenile and weanling alpacas. We have not yet seen a case in a llama, but there is little reason to think that this will not occur. Rickets in these growing animals causes distortion of the growth of the long bones, those most affected being the radius and tibia. These abnormalities cause the legs to become very crooked in a slowly progressive manner, often appearing “knock-kneed” or “bow-legged.” These juveniles often have a history of very normal conformation in the first few weeks of life, but they become more distorted as they become heavier and older. Minimal lameness and gait abnormality is often noticed.
Rickets, as described, is caused by a deficiency in serum Calcium and Phosphorus. It can be caused by a deficient ration or a decrease in Vitamin D. Vitamin D deficiency is the most common cause of Rickets within the new world camelids. Vitamin D is produced by the skin upon exposure to natural sunlight. It is also found in grasses and forages exposed to sunlight. In the alpaca and llama, the problem seems to be more prevalent in crias with very dense fleece. It is worst in those with dense fiber on the face, ears, and legs. The sunlight probably does not adequately penetrate the fleece on these animals. Abnormally low levels of Calcium and Phosphorus during a period of rapid growth can cause the bones to grow in an irregular manner. The bones will be weaker, less dense, and more prone to bending/breaking.
Diagnosis is normally made by using their typical history, blood Vitamin D concentration, and radiographs. If significant evidence is present, we would then initiate therapy with injectable Vitamin D (30,000 IU IM once per week for 3-4 weeks). Improvement can be dramatic, but changes are slow. These animals should also be exposed to as much sunlight as possible. Do not keep them confined in a barn and in some cases they should be forced to remain out of run-in sheds, etc. during daylight hours. Feed as much high quality grass hay as possible and give them the best open pasture while limiting excessive exercise.