Hyperextension of the metacarpophalangeal and metatarsophalangeal joints can affect camelids of any age and may ultimately lead to degenerative joint disease, soft tissue calcification, and decreased ambulation.1 Previous studies2–4 have characterized metacarpophalangeal and metatarsophalangeal hyperextension in llamas by ultrasonographic, radiographic, biochemical, and molecular techniques. In juvenile llamas, there is evidence of collagen and proteoglycan changes associated with trauma and healing of the suspensory ligament.4
Trace mineral alterations have also been found in llamas with metacarpophalangeal and metatarsophalangeal hyperextension. A previous study2 of mainly adult llamas identified low liver copper and high serum zinc concentrations in affected llamas. However, when solely adult llamas were compared, differences were not significant, although high serum zinc concentration was found in affected llamas (P = 0.08), likely because of the low number of animals (6 affected animals and 6 control animals). A follow-up study in juvenile llamas4 revealed high serum molybdenum and low liver cobalt concentrations in llamas with this condition. Although liver samples provide superior results for trace mineral analysis, there is no minimally invasive means of obtaining sufficient liver tissue in a field setting. Serum samples offer the next best alternative, as they are easy to obtain and yield adequate results to help differentiate affected from unaffected animals.
Concentrations of estradiol, progesterone, and testosterone have not been determined in camelids with metacarpophalangeal and metatarsophalangeal hyperextension. Data on these sex steroid hormones will help to determine whether there is an association with this disease because estrogen is thought to play a role in ligament injury in other species.5 In addition, low vitamin D concentrations have been found in juvenile camelids with developmental orthopedic disease, including angular limb deformities and physeal abnormalities,6 but it is not known whether vitamin D plays a role in metacarpophalangeal and metatarsophalangeal hyperextension of camelids.
Speculation by owners and veterinarians regarding environmental and hereditary factors associated with metacarpophalangeal and metatarsophalangeal hyperextension is common. However, demographic data and herd management information have not been reported in camelids with this disease.
Therefore, the objective of the study reported here was to evaluate serum trace mineral, vitamin D, and sex steroid hormone concentrations and identify factors associated with metacarpophalangeal and metatarsophalangeal hyperextension in llamas and alpacas. The hypothesis was that serum trace mineral imbalances, including low copper and high zinc concentrations, and high estradiol and low vitamin D concentrations would be found in affected animals, compared with controls.
Diagnostic Center for Population and Animal Health, Michigan State University, Lansing, Mich.
Endocrinology Laboratory, Animal Health Diagnostic Center, College of Veterinary Medicine, Cornell University, Ithaca, NY.
Stata/IC, version 11.2, StataCorp, College Station, Tex.
Statistix, version 1, Analytical Software Inc, Tallahassee, Fla.
Pollard's Camelid Tendon Repair Herbal Blend, Starwest Botanicals Inc, Rancho Cordova, Calif.
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