Morphological variation of "complex vertebral malformation" in Holstein calves.

A study was performed to investigate the morphological expression of the inherited syndrome "complex vertebral malformation" (CVM) in Holstein calves. A total of 107 late-term aborted, premature, or neonatal calves suspected of having CVM were necropsied and retrospectively analyzed for the causal mutation in the gene SLC35A3. Sixty-two calves were homozygous affected, 16 were heterozygous, and 29 were homozygous normal. Calves affected by CVM were growth retarded. Vertebral lesions identified by radiography were present in 61 cases, of which 58 also had costal malformation. Malformation of the head, primarily in the form of dysplasia or palatoschisis, was present in 15 cases. Bilateral symmetric flexion of the carpal and metacarpophalangeal joints was present in all cases, whereas posterior arthrogryposis was found in 54 cases. Interventricular septal defects occurred in 33 calves, often in combination with other cardiac malformations. A wide spectrum of additional malformations was found. Other congenital syndromes were in most cases distinguishable from CVM on a morphological basis. However, a calf with a prenatal infection with bovine virus diarrhea virus constituted a phenocopy. The study demonstrated that the morphological expression of CVM is wide, but certain aspects, i.e., growth retardation, vertebral malformation, and symmetric arthrogryposis, are almost constant findings. However, cases without vertebral defects and phenocopies constitute a diagnostic problem. A presumptive diagnosis of CVM can in most cases be based on necropsy findings combined with information on descent and paternal CVM genotype, whereas a definitive diagnosis requires genotyping.