Congenital musculoskeletal disease associated with selenium deficiency in calves in Argentina

On two occasions, increased perinatal losses were reported in two beef cattle herds under extensive rearing conditions in Buenos Aires province, Argentina, during the winter calving season of 2025.

Affected calves were born weak, unable to stand and suckle, and died within 1-3 days of birth. Cumulative incidences of 10% (33/330) and 3.9% (12/305) were recorded, with 100% case fatality.

Necropsies were performed on three calves: two from Outbreak 1 (one calf died within 1 day of birth and one within 3 days) and one calf that died within 1 day of birth from Outbreak 2. Grossly, in all three calves, pelvic limbs and sublumbar muscles exhibited multifocal-to-coalescent pale whitish discolouration, interspersed with haemorrhage. Microscopically, skeletal muscles presented polyphasic degeneration and necrosis of myofibres with calcified deposits within the sarcoplasm. Low Se concentrations (<0.75 mg/kg) were detected in the livers of all three calves, while Cu and Zn concentrations were within reference ranges. No evidence for the involvement of infectious agents was detected. Low Se concentrations were observed in serum samples from 18 dams from Outbreak 1 and nine from Outbreak 2. Mineral analysis of available feed from both farms showed low Cu concentrations in both outbreaks and elevated S concentrations in Outbreak 2.

Nutritional myopathy (NM) in beef calves, presumed to be associated with Se deficiency in calves born to Se-deficient dams.

Se deficiency was the most likely cause of NM, but high dietary ${\mathrm{SO}}_4^{-2}$ and S concentration in Outbreak 2 may have interfered with dietary Se absorption. Our study highlights that NM should be considered as a potential cause of perinatal losses.