Early-onset muscle weakness syndrome (MW) in an Australian Holstein calf.

Early-onset muscle weakness syndrome (MW) is a recessive genetic disorder known to affect Holstein cattle. This report describes the clinical findings in an Australian Holstein calf diagnosed with MW. The calf initially presented for examination at a dairy farm at 3 days of age, being recumbent since birth but able to stand with assistance. A presumptive diagnosis of traumatic injury was made at first. However, the calf was re-examined multiple times due to ongoing intermittent episodes of recumbency, prompting further diagnostic investigation. Given the non-specific nature of the clinical and laboratory findings, a presumptive diagnosis of MW was made after reviewing the calf's breeding pedigree. A definitive diagnosis, however, required genotype testing. To the authors knowledge, this case report represents the first peer-reviewed manuscript to describe the clinical presentation of MW in an Australian Holstein calf.