Heifer sterility associated with single-birth freemartinism

Area of Science:

• Veterinary Science
• Reproductive Biology
• Cytogenetics

Background:

• Infertility in cattle can stem from various genetic and developmental factors.
• Sex-chromosome chimerism, often associated with twin pregnancies, can lead to reproductive anomalies.

Observation:

• Karyotyping of 34 infertile heifers revealed 12 sex-chromosome chimeras, including five single-born individuals.
• Post-mortem examination of three singleton chimeric heifers showed significant reproductive tract abnormalities.

Findings:

• Heifers with varying percentages of male cells exhibited conditions like non-patent cervices, uterine horns, and rudimentary gonads.
• One heifer displayed intersex characteristics with seminal vesicles and gonadal structures resembling fetal testes.

Implications:

• Cytogenetic analysis confirms the existence of single-born freemartins resulting from fetal vascular anastomosis.
• These findings are crucial for understanding bovine infertility and reproductive health in chimeric cattle.