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freemartinism in other species
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<blockquote data-quote="Keren" data-source="post: 373246" data-attributes="member: 3195"><p>After 2 - 3 weeks (cattle, sheep and goats) the conceptus settles in one of the horns but the extra-embryonic membranes (placental membranes) cover both the gravid (inhabited) horn and some of the non-gravid horn. This is essential for maternal recognition of pregnancy - the membranes must cover a certain proportion of the uterus in order for the mother to recognise the pregnancy and maintain the hormones which sustain the embryo. In polyoctus species (more than one embryo ie pigs), intrauterine migration occurs to evenly space the embryos to cover the uterine surface for maternal recognition of pregnancy and thus embryo survival.</p><p></p><p>From this I would hazard a guess that in cattle bearing two embryos, the spread of the extra-embryonic membranes into both horns results in the contact of placentas and the blood exchange that milkmaid spoke about. Intrauterine migration is rare in single embryo species, thus the embryos cannot avoid the placental contact. </p><p></p><p>Obviously pigs do not display freemartinism, as the extra-embryonic membranes rarely connect, due to the intrauterine migration and spacing. </p><p></p><p>As for goats not displaying freemartinism, I'm still unsure why this is. Perhaps the goat conceptus does not spread as much into the non-gravid horn, or some intrauterine migration occurs to space the embryos more evenly. </p><p></p><p>If anyone could shed more light on the subject, I would be interested to hear it.</p></blockquote><p></p>
[QUOTE="Keren, post: 373246, member: 3195"] After 2 - 3 weeks (cattle, sheep and goats) the conceptus settles in one of the horns but the extra-embryonic membranes (placental membranes) cover both the gravid (inhabited) horn and some of the non-gravid horn. This is essential for maternal recognition of pregnancy - the membranes must cover a certain proportion of the uterus in order for the mother to recognise the pregnancy and maintain the hormones which sustain the embryo. In polyoctus species (more than one embryo ie pigs), intrauterine migration occurs to evenly space the embryos to cover the uterine surface for maternal recognition of pregnancy and thus embryo survival. From this I would hazard a guess that in cattle bearing two embryos, the spread of the extra-embryonic membranes into both horns results in the contact of placentas and the blood exchange that milkmaid spoke about. Intrauterine migration is rare in single embryo species, thus the embryos cannot avoid the placental contact. Obviously pigs do not display freemartinism, as the extra-embryonic membranes rarely connect, due to the intrauterine migration and spacing. As for goats not displaying freemartinism, I'm still unsure why this is. Perhaps the goat conceptus does not spread as much into the non-gravid horn, or some intrauterine migration occurs to space the embryos more evenly. If anyone could shed more light on the subject, I would be interested to hear it. [/QUOTE]
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