Author Topic: Freemartins (Read 6087 times)

princesspiggy · « **on:** September 11, 2012, 08:37:10 pm »

i learnt something new today. not just related to cattle but goats, sheep, pigs etc too.
Freemartins - a cause of infertility in livestock. thought it might interest some of you

unless im the only one who didnt know.

A freemartin or free-martin (sometimes martin heifer) is an infertile female mammal which has masculinized behavior and non-functioning ovaries. Genetically the animal is chimeric: karyotyping of a sample of cells shows XX/XY chromosomes. [The animal originates as a female (XX), but acquires the male (XY) component in utero by exchange of some cellular material from a male twin, via vascular connections between placentas.] Externally, the animal appears female, but various aspects of female reproductive development are altered due to acquisition of anti-Müllerian hormone from the male twin. Freemartinism is the normal outcome of mixed-sex twins in all cattle species that have been studied, and it also occurs occasionally in other mammals including sheep, goats and pigs.
The 18th-century physician John Hunter discovered that a freemartin always has a male twin.
It was hypothesized early in the 20th century that masculinizing factors travel from the male twin to the female twin through the vascular connections of the placenta because of the vascular fusion and affect the internal anatomy of the female.
In most cattle twins, the blood vessels in the chorions become interconnected, allowing blood from each twin to flow around the other. If both fetuses are the same sex this is of no significance, but if they are different, male hormones pass from the male twin to the female twin. The male hormones then masculinize the female twin, and the result is a freemartin. The degree of masculinization is greater if the fusion occurs earlier in the pregnancy – in about ten percent of cases no fusion takes place and the female remains fertile.

The male twin is largely unaffected by the fusion, although the size of the testicles may be slightly reduced. Testicle size is associated with fertility, so there may be some reduction in bull fertility.

If suspected, a test can be done to detect the presence of the male Y-chromosomes in some circulating white blood cells of the subject.
A freemartin is the normal outcome of mixed twins in all cattle species which have been studied. It does not normally occur in most other mammals, though it has been recorded in sheep, goats and pigs.

anyone experienced it?

robert waddell · « **Reply #1 on:** September 11, 2012, 09:06:53 pm »

yes in a heifer i had bought in as a replacment

also know as a jenny wilox (spelling)

Beewyched · « **Reply #2 on:** September 11, 2012, 09:11:19 pm »

Never heard of it before Julia - it's a new one for me.
Thanks for the info

domsmith · « **Reply #3 on:** September 11, 2012, 09:29:22 pm »

we used to rear dairy bulls forr veal, as part of our gathering of bull calves from various dairies we would be given heifers that were twins to bulls.
i always ussed to keep an eye on them, and some would develope udders and look normal, some would have no udder at all.

the one that looked promising i would not kill at 9 months and see what happened, we did get some in calf which was great.
but most are free martins!
never seen it in sheep, or pigs.

d

YorkshireLass · « **Reply #4 on:** September 11, 2012, 09:30:40 pm »

I think the placenta structure is different in sheep (pigs?) so the transfer of testosterone etc shouldn't happen

princesspiggy · « **Reply #5 on:** September 11, 2012, 09:33:06 pm »

apparently its more rare in pigs/sheep, that would be a pig nightmare wouldnt it?

robert waddell · « **Reply #6 on:** September 11, 2012, 09:41:45 pm »

maybe not so rare as folk think if a gilt does not get in pig you kill it not give it an examination same with boars that dont work

princesspiggy · « **Reply #7 on:** September 11, 2012, 09:51:08 pm »

http://www.thecattlesite.com/articles/975/what-is-a-freemartin

SallyintNorth · « **Reply #8 on:** September 12, 2012, 12:18:06 am »

It is normally assumed that the heifer twin to a bull calf will be infertile, so she'll be reared for meat. It will be mentioned when selling that she's a twin to a bull calf, so the buyer can decide whether she's for him or not. It sounds as though some will come a-bulling, so would probably sell to folk who run heifer-only units anyway.

It is normally assumed that the ewe twin to a tup lamb will be a normal breeding female. Occasionally you get a masculine-looking sheep who never has a lamb, perhaps she was a freemartin? She'll often be spotted by the shearer - I had one exclaim, "She's a man!" and indeed she did look different to the other mules, and she had no udder development at all although she was old enough to have had two crops. Because it was a new experience to us (this was in my early years on the moorland farm, not here with BH), we gave her a shot at the tup but she was never tupped, so we got her away geld.