Spinal muscular atrophy in calves of the Red Danish dairy breed.

Pathological and genetic aspects of spinal muscular atrophy in Red Danish dairy cattle are described. A total of 312 calves suspected of having the condition was reported in the Danish Bovine Genetic Disease Programme, 162 of them were examined post mortem and spinal muscular atrophy was diagnosed in 82 of these. Seventy-five per cent of the affected calves had bronchopneumonia. The diagnosis of spinal muscular atrophy was based on histopathological examinations of the spinal cord and musculature. The lesions were primarily characterised by degeneration of the spinal cord motor neurons with neuronophagia and denervation muscular atrophy. The ages of the affected calves varied from those recumbent from birth to a 21-week-old calf. All the necropsied cases appeared in a clearly familial pattern and could be traced back to American Brown Swiss bulls.