Chromosomal aneuploidy associated with spontaneous abortions and neonatal losses in cattle.

Pericardial sac samples from 77 bovine aborted fetuses and stillborn calves were submitted for tissue culture; cells from 55 of these samples were grown successfully in culture. Six of the 55 karyotyped fetuses (10.7%) had an abnormal chromosome complement, in 3 of which (5.5%) the abnormality was probably the cause of death. This level of abnormality is relatively high when one considers that most fetuses were >8 months gestational age. Approximately 5-7% of human stillbirths and 50% of first-trimester aborted fetuses have chromosome anomalies. If a similar situation exists in cattle, as suggested by these data, chromosome abnormalities may be a major cause of early fetal loss in cattle. Most chromosomally abnormal fetuses had multiple malformations, which suggests that the diagnostic use of chromosome analysis is most cost effective for malformed fetuses and newborns. Twins were present in a higher proportion of these fetuses than expected based on their incidence among liveborn cattle.