Free martin

about free martinism

1. FREE MARTIN

2. Dizygotic twins The most frequent form of twins are the dizygotic ones (7 to 11 in 1000 deliveries), also known as "sibling twins" or "false twins". These twins stem from two oocytes that matured during the same menstruation cycle and were fertilized by two different sperm cells. In other words, genetically, the two zygotes that arose with the fertilization differ just as much as two normal siblings. Thus dizygotic twins can be of the same or opposite sex. Dizygotic twins  implant themselves separately and develop membranes that are independent of each other. Each twin has its own placenta, its own chorion and its own amniotic cavity. It sometimes happens that the two placentas lie so close to each other that they fuse; the same thing can also occur with the chorions of the two twins. Thus immunologic incompatibility reactions can be observed since the fusion of the two placentas makes an exchange between the circulation systems possible.

3. Day 22 -23 – allantochorion formed Day 40 – sexual differentiation

4. Freemartinism is one of the most commonly found intersex conditions in cattle although it may also occur in small ruminants. 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

5. A freemartin is, by definition, a genetically female fetus masculinised in the presence of a male co-twin, giving rise to a sterile heifer A bovine freemartin is usually defined as a sterile female calf, born co-twin with a male fetus that shows underdeveloped or misdeveloped genital tract as a result of early development of vascular anastomoses between fetuses of different gender

6. Features of genital tract 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 cordlike 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.

7. Absence of anatomical continuity between the vagina and the uterus, hypoplastic or absent uterus, and hypoplastic or streak gonads, co-existing with vesicular glands, are common findings in freemartin heifers

8. As consequence of placental anastomoses between the heterozygotic twins, blood chimaerism occurs (60, XX/XY) and passage of male gonad determinants or hormones (such as AntiMüllerian hormone and androgens) are responsible for disrupted differentiation of the female embryonic gonads and disturbed genital tract development

9. Diagnosis The freemartin condition may be diagnosed on the basis of physical examination of suspected animals, as well as by serologic or cytogenetic testing; the later being more expensive and not always well accepted by the farmer, who often considers it an unnecessary expense.

10. It should be emphasized the importance for discarding the freemartin syndrome during a reproductive evaluation whenever a heifer is intended to be maintained in the farm for replacement. Its inability to reproduce demands its early detection and culling from the herd