Klinefelter syndrome in a Holstein-Friesian bull: a case report.

BACKGROUND

This report describes the clinical, laboratory, and post-mortem findings in a 16-month-old Holstein-Friesian bull diagnosed with Klinefelter syndrome, a rare sex chromosome disorder characterised by testicular hypoplasia and infertility. CASE PRESENTATION: During the routine genotype quality control process, the bull was flagged as a suspected XXY (Klinefelter syndrome) based on its genotype data. Analysis of parental genotype data revealed the bull inherited one X chromosome from each parent, indicating a paternal nondisjunction event. Karyotyping subsequently confirmed the 61,XXY chromosome complement. Clinical examination revealed the bull had normal libido with normal testosterone concentration (13.1 nmol/ml) but had a small scrotal circumference (18.5 cm). Post-mortem examination revealed that the bull had bilateral testicular hypoplasia and azoospermia. These findings were consistent with other reports of Klinefelter syndrome in bulls.

CONCLUSION

This case highlights the importance of the national genotyping screening program to identify infertile bulls (and females) that should not be considered for breeding. The clinical and post-mortem observations add to the limited veterinary literature on bovine Klinefelter syndrome presentations.