Abstract
A homozygous calf with CACNA1S-related muscle weakness, a new autosomal recessive congenital disorder in Holstein cattle, was identified by genotyping 195 stored blood samples from Holstein calves aged less than 12 months. The patient was an 8-day-old male calf with congenital astasia which presented to a university hospital in 2019. The patient was unable to maintain an upright position with assistance to stand. Congenital abnormalities in the central nervous system were suspected, but necropsy revealed no specific lesion, with no clear diagnosis. CACNA1S-related muscle weakness should be considered a cause of congenital astasia or weakness in calves. Genotyping is required for a definitive diagnosis because clinical and laboratory findings are non-specific.