what determines gender?

Discussion in 'Incubating & Hatching Eggs' started by HillCountryMomma, May 23, 2008.

  1. HillCountryMomma

    HillCountryMomma Songster

    Mar 16, 2008
    Ok, no one laugh... I posted this under another topic but no answer yet so I'm posting it here too.

    Does the rooster determine gender like a human male does, or is it some other factor with chickens?

    I've had three batches of chicks from my rooster this year, and we're leaning heavy on the girls. Yea!!!! [​IMG]

    Just wondering if it's him, other conditions, or blind luck.

    I've had 10 chicks hatch out under my broody in the last 2 days (black sex links) and 8 of the ten are pullets! The other two hatches were small and resulted in 5 pullets & 3 roosters. I'm liking those ratios!

  2. coopist

    coopist Songster

    Jan 2, 2008
    Midwest U.S.
    Actually, in chickens, the hen determines the offspring's gender--just the opposite of humans.
  3. kees

    kees Songster

    Feb 5, 2008
    Really? That's very interesting! How does that work?
  4. DuckyBoys

    DuckyBoys Songster

    Apr 2, 2008
    Next, approaching birds, we begin to tread on more familiar ground, as once again we return to sex chromosomes. In birds however, females are the heterogametic sex, carrying one copy of each of the so called Z and W sex chromosomes, whereas males are homogametic ZZ. The Z and W chromosomes have no relation to the mammalian X and Y, and in fact seem to have evolved from different pairs of autosomes. And this is part of the reason we are not yet certain which of the two carries the genetic trigger for sex determination [38,39].

    To this day, there are two major theories under investigation. Sex may depend on Z chromosome dosage, according to the example of Drosophila melanogaster and C.elegans. One candidate gene for this theory is the DMRT1, which is located on Z chromosomes, escapes dosage compensation and is expressed specifically in the gonads, and is thus capable of linking the number of Z chromosomes with gonadal differentiation [40,41].

    On the other hand, sex may be determined by the feminizing presence of the W chromosome, following the example of Y in eutherian mammals. There are two different mechanisms that are being studied and can support this theory. One includes the FET1 gene, which is located on W, does not have a Z homologue and is expressed almost exclusively in the female urogenital system [18]. The other includes the ASW gene, also known as WPKCI, and its Z homologue ZPKCI, since it has been proposed that the products of those two genes are capable of dimerisation, with a ZPKCI homodimer acting as a testis factor and a WPKCI/ZPKCI heterodimer preventing this effect (see Figure 14) [39-41].

    Molecular patterns of sex determination in the animal kingdom: a comparative study of the biology of reproduction​
  5. seriousbill

    seriousbill Songster

    May 4, 2008
    That is great info DuckyBoys [​IMG] , but allow me to translate that to English for the folks down home [​IMG]

    Okay, so, the roo has sex chromosomes ZZ and the hen has ZW. This is similar to, but different from, the human XX and XY. For all intents and purposes, though, it works in a similar way. If the chick gets a Z from momma, it's a roo. If it gets a W, it's a hen. They don't know if it's because it takes a lot of Z to make a roo, or if the W is a special hen-making chromosome. Either way, the effect is the same, and the W makes a hen.

    Btw, I've read that good nutrition can make a slight difference in the number of female offspring produced in some bird species (that is, you get a few more females when hens are well fed). Don't know if it applies to poultry, but it might be one more good reason to feed those chickens well [​IMG]
    Last edited: May 23, 2008
  6. HillCountryMomma

    HillCountryMomma Songster

    Mar 16, 2008
    Thank you for the fascinating info!

    So, I guess Big Red is expendable after all. [​IMG] Poor guy, he just had his value totally deflated!

    I'm curious about good feed = more females theory. My hens are 100% free range, get 10% protein scratch, all household scraps, oyster shell and that's it. They are cleaning up leftover chick starter as I move tractors of babies around right now, but not enthusiastically. They flat out refuse to eat layer pellets, haven't tried crumbles yet. Oh... they eat my old mares high fat grain pellets when she drops them. They act like that stuff is candy!

    I've found it really interesting watching my birds eat. The older chicks are free range during the day now. I let them out of their tractor, put down a big pan of feed (1/2 chick starter, 1/4 scratch, 1/4 cracked corn). They take a few mouthfuls, and scatter to the 4 corners of the yard to munch grass and chase bugs. They were eating 1 1/2 pans of feed a day before I let them out of the tractor to range. Now they are not even finishing one pan of feed, and my adult birds have access to it as well.

    Apparently, my chickens would rather hunt down their own meals than eat processed feed!
  7. farmgirlie1031

    farmgirlie1031 Songster

    Apr 26, 2008
    Quote:I hope I get those results. Of my straight run purchases I got almost all roos. I have my first hatch due Monday from my own hen and Wed. from my purchased fertile eggs. I was told it was incubator temp that determines sex. Glad you asked the question and got anwsers so I could learn also.
  8. Zookeeper9000

    Zookeeper9000 Songster

    Mar 1, 2008
    Gladstone MI
    I was told a old wise tale but a lady I got my dorking eggs from. She has been experimenting with it for 2 years and has a 98% success rate for hens. She was told that the eggs with a point to the small end was roo's and when the small end of the eggs is oval or rounded they are hens. She swears by it. Me I am keeping track of my oval and round eggs verses my pointed eggs and I will see. Just thought ya might want to know in case ya want to try your hand at seeing if it is true.

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