Freemartins: black sheep among the cattle

News Excerpt:
In animal husbandry, cattle born exhibiting characteristics of both sexes are called freemartins.

About Freemartins:

  • Freemartins are sterile female cattle from twinning males and females within the same uterus. 
  • This phenomenon occurs in approximately 90% of such twin pregnancies in cattle. 
    • The key reason is the blood exchange between the male and the female foetuses during gestation.
  • Genetically, freemartinism is attributed to sharing cells carrying the Y chromosome from the male twin with the female twin. 
    • This chromosome triggers the development of male reproductive organs in the male foetus, while the female foetus, affected by male hormones, experiences incomplete development of its reproductive system. 
    • The result is that the freemartin has an underdeveloped or non-functional reproductive tract.

  • A joining of the placental membranes occurs at about the fortieth day of pregnancy, and after that, the fluids of the two fetuses are mixed. 
  • This causes the exchange of blood and antigens, carrying characteristics unique to each heifer and bull. 
  • When these antigens mix, they affect each other in a way that causes each to develop with some characteristics of the other sex.
  • Although the male twin, in this case, is only affected by reduced fertility, in over ninety percent of the cases, the female twin is completely infertile.
  • The ovaries of the freemartin do not develop correctly and remain very small. 
  • Also, the ovaries of a freemartin do not produce the hormones necessary to induce the behavioural signs of heat.
  • Freemartinism cannot be prevented; however, it can be diagnosed in several ways, from simple examination of the placental membranes to chromosomal evaluation.