Freemartinism in Cattle
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2012
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Freemartinism is one of the most commonly found intersex conditions in cattle, although it
may also occur in small ruminants. The freemartin phenotype appears in a dizygotic twin
pregnancy where one twin is a male and the other is a female. Due to precocious anastomoses
between the placental vascular systems of the two fetuses, masculinising molecules reach the
female twin and disrupt the normal sexual differentiation, whilst in the male the effects of this
association are usually minimal. In cattle, this condition is observed in 90 to 97% of twin
pregnancies.
A freemartin is, by definition, a genetically female fetus masculinised in the presence of a
male co-twin, giving rise to a sterile heifer. Genital tract defects with varying severity can be
observed in freemartin animals, which often present suppression and disorganization of the
ovary, originating a rudimentary or a testis-like gonad depleted of germ cells. The uterine
horns may be hypoplastic or instead may be reduced to a cord-like structure suspended in the
broad ligament. Anatomic continuity between the uterus and the vagina is frequently absent,
and the existence of rudimentary vesicular glands is typical. The external genitalia commonly
presents enlarged clitoris, small vulva and a prominent, male-like tuft of hair. As a rule,
heifers born twin to a bull have to be considered sterile and should be identified as early as
possible to cull them from replacement stock. Despite its limitations, freemartinism is
currently diagnosed by physical examination, as karyotyping or blood typing is often
considered an unnecessary expense.
In cattle, twinning trend has a genetic background that has been associated to hormonal
regulation in favor of double ovulations. However, the genetic determinant on the basis of
twinning seems to have small importance when compared to environmental or managementassociated
factors, particularly in dairy cows. In fact, in dairy animals, in particular in high
milk producing cows, it has long been proven the increase of twin calvings due to the
hormonal and metabolic disturbances in the energy balance early in the post-partum period.With increased incidence of twin births in cow it is reasonably expectable a small increase in
the occurrence of freemartins at the farm levels. In this paper it is the intent to describe the
gross and histopathological findings of freemartinism in cattle, using data gathered from a
study at an abattoir (17 cases) and from 3 cases diagnosed in living animals, supported by a
review of the pathophysiology of the process, and to discuss the available methods for
identification of freemartin animals at farm level.