bovis - Articles
Freemartinism
Synonym(s): masculinisation, masculinization, twin
Introduction
- Cause: fusion of blood vessels within the placenta of mixed sex twin conceptuses resulting in H-Y antigen (anti-Mullerian duct hormone) and testosterone secreted by the earlier sex differentiating male conceptus influencing the sex differentiation of the female conceptus.
- Treatment: none.
- Prognosis: guarded - poor for breeding (~8% female twins born to mixed sex pregnancies are sterile).
Geographic incidence
- Worldwide.
Breed/Species predisposition
- All breeds.
Public health considerations
- None.
Cost considerations
- Important to identify freemartins early to enable economic culling of non-breeding animals.
- Will fatten for meat.
Pathogenesis
Etiology
- Phenotypic female born co-twin to a male.
- Sexual differentiation occurs earlier in the male embryo.
- Anastomoses between the placental (chorionic) blood vessels of the different sex twins allows transfer of male tissue specific antigen (H-Y antigen / identical to Mullerian-inhibiting substance) to the female twin, which inhibits development of the female gonad.
Pathophysiology
- Variable abnormalities of the genital organs, ranging in severity depending on when the fusion / anastomosis of blood vessels occurred.
- Hypoplastic ovaries (often contain seminiferous tubules)
. - Absence of cervix.
- Cord-like uterine horns (occasionally near normal size).
- Blind-ending, shortened vagina.
- 5 - 6 cm in freemartin cf 13 - 15cm in normal female aged 1 - 4 weeks.
- 8 - 10cm in freemartin cf 20 - 30cm in normal female adult cattle.
- Hypoplastic ovaries (often contain seminiferous tubules)
Timecourse
- Short vaginal length apparent from birth.
- Features become more pronounced as the animal ages.
Epidemiology
~82 - 90% phenotypic females born twin to a male are freemartins.Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed Papers
- Recent references from PubMed and VetMedResource.
- Long S E (1990) Development and diagnosis of freemartinism in cattle. In Practice (12), 208-210.
Other sources of information
- Andrews, Blowey, Boyd & Eddy (2008) Bovine Medicine. 2nd edn. pp 183-184.
- Smith (2002) Large Animal Internal Medicine. 3rd edn. pp 1301.
- Jones, Hunt & King (1997) Veterinary Pathology. 6th edn. pp 1155-1156.