Carpal hyperextension in Nigerian Dwarf goats is a heritable syndrome associated with lameness and forelimb deformity.

Abstract

OBJECTIVE: To characterize an acquired carpal hyperextension syndrome reported by North American owners of Nigerian Dwarf goats and examine potential genetic associations. METHODS: Affected (cases) and unaffected (controls) Nigerian Dwarf goats were recruited into this observational study from 2022 to 2023 through a small ruminant producer email list and social media. Animals with reported limb trauma, cases with mild carpal angulation, and controls under 2 years old were excluded. Physical examination, carpal goniometry and blood mineral analysis were performed on all animals. Husbandry and registration information were recorded by a standardized questionnaire. Imaging and histopathology were performed on a subset of cases. Pedigrees were analyzed for common ancestor(s) with Pedigraph. A genome-wide association study was performed with the Illumina GoatSNP50 array. RESULTS: 36 cases (carpal angle > 187°) and 64 controls were included. Owners recognized cases at a median age of 12 months (IQR, 12 to 24 months; range, 3 to 36 months); lameness was common in cases. Median standing carpal angle of cases when bearing weight was 193.3° (IQR, 190.2° to 198.3°) versus 180.3° in controls (IQR, 180.0° to 180.7°). Imaging and histopathology did not identify a structural cause. Blood mineral concentrations were similar between groups. Pedigree analysis indicated all cases shared a single ancestor. Genome-wide analysis identified a region of interest (chr24:59,830,666-60,251,280) associated with the hyperextension phenotype. CONCLUSIONS: Carpal hyperextension in Nigerian Dwarf goats was often associated with lameness and appears heritable. CLINICAL RELEVANCE: Small ruminant producers and veterinarians should be alert to this potentially heritable condition. Carpal goniometry of standing animals represents an inexpensive and minimally invasive diagnostic procedure.