Soooooo.... it appears you CAN manipulate the sex ratio on your chicks

Discussion in 'Chicken Behaviors and Egglaying' started by onthespot, Dec 6, 2009.

  1. onthespot

    onthespot Deluxe Dozens

    Mar 29, 2008
    Riverside/Norco, CA
    Mother Birds Increase Progesterone To Hatch Females


    ScienceDaily (May 17, 2005) — ITHACA, N.Y. -- In mammals, sperm from the male determines the sex of the offspring. In birds, however, it is the female's sex chromosome that determines offspring sex. Now, Cornell University researchers think they understand the mechanism that several bird species use to bias the sex ratios of their offspring toward female.

    By experimenting with domestic chickens, they have determined that the presence of higher-than-normal levels of the hormone progesterone during the first meiosis -- the cell division that divides the sex chromosomes and genetically determines the sex of an offspring -- produces significantly more females.

    "For years, behavioral biologists have been trying to figure out how the females of a few species, such as the Seychelles warbler, the zebra finch and tree swallow, adaptively manipulate the sex of their offspring before an egg is laid," says Stephanie Correa, a doctoral student in neurobiology and behavior at Cornell and the lead author of the study that was posted online recently in The Royal Society's Biology Letters (Vol. 1, 2005). "Most investigators have looked primarily at testosterone, but we decided to look at progesterone, the major hormone produced by the female bird's preovulatory follicle."

    To test the influence of progesterone on the sex ratio of offspring, Correa, along with Elizabeth Adkins-Regan, professor of neurobiology and behavior and of psychology, and Patricia Johnson, professor of animal science, both at Cornell, experimentally manipulated levels of progesterone in female chickens during the first meiosis. They injected either a low dose or a high dose of progesterone (dissolved in sesame oil) or a control dose of pure sesame oil.

    The low dose of progesterone produced 61 percent males, which was very close to the control group rate of 63 percent males. The high dose of progesterone, however, produced only 25 percent males.

    "Thus, we think that how much progesterone the female follicle produces during the first meiosis is the mechanism in birds that manipulates the sex ratio of offspring," says Adkins-Regan.

    "Researchers think that birds such as the Seychelles warbler may bias the sex of their offspring when, for example, their territory has plenty of food and the mother bird needs help in feeding the next generation," says Correa. Since males disperse, the mother bird may adaptively bias her offspring to female so that plenty of females from one generation will be available to help raise the next generation.

    Although the finding is not of practical use in the near future for the poultry industry, Correa and Adkins-Regan say that understanding the basic mechanism of biasing sex ratios in birds could provide the foundation for learning how to manipulate the sex ratio of avian offspring in the future. Research in this area is just beginning, they note, because the molecular methods used to determine the sex of the eggs has only recently been made available.
  2. cluckcluck42

    cluckcluck42 Chillin' With My Peeps

    Oct 4, 2009
    That's frickin cool!!! Great info, thanks.
  3. FireTigeris

    FireTigeris Tyger! Tyger! burning bright

    Next step-

    foods that increase progesterone in chickens w/o increasing significantly the risk of cancer. :

    suggested that avocados (<-proposed unsafe for chicken) , nuts and seeds, olives and oils are progesterone-boosting foods. I also read on Wikipedia that a diet rich in dairy can elevate progesterone levels, as the cows are milked during pregnancy when their own levels are elevated. Plants such as the soy bean, Dioscorea species of yams, fenugreek and many more, contain phytosterols, two such are stigmasterol and diosgenin.

    As these sterols have a similar molecular structure to progesterone, they are used as starting points for the bio-synthesis of progesterone. This is then further broken down to oestrogen, testosterone, cortisol etc for use in HRT, testosterone replacement, cortisone etc. :

    Plant Progesterones
    1. Wild yam is famous for containing hormone-like compounds that are very similar to progesterone, and it may encourage the body's own production of the hormone. Bear in mind that the sweet potato, a different vegetable, does not contain these compounds.
    True Progesterone
    2. Egg yolks and dairy products both contain respectable amounts of true progesterone, but it is not known how directly they interact with the human body's own progesterone stores.
    Foods with Vitamin B-6
    3. Walnuts, whole grains, fortified cereals, and soy milk all contain large amounts of vitamin B-6, which is essential for maintaining ideal estrogen-progesterone balance.
    Foods Containing Zinc
    4. Zinc is essential to producing adequate levels of progesterone, so high-zinc foods like red meat, shellfish, chicken, and turkey can all increase progesterone levels.
    Culinary Herbs
    5. Turmeric, found in curry, can increase the body's progesterone levels, as can thyme and oregano. Including one of these in every meal may help to maintain good hormone balance.​
    Last edited: Dec 6, 2009
    tessachick likes this.
  4. CityGirlintheCountry

    CityGirlintheCountry Green Eggs and Hamlet

    Jul 7, 2007
    Middle TN
    So an interesting experiment might be to feed hens a mix of yams, dairy, walnuts, etc and see how the male/female ratios turn out. Even better would be if someone on here had a hen that laid predominantly male offspring, change the diet and see if that tendency could be changed.

    Interesting info. Thanks for sharing!
  5. Happy Chooks

    Happy Chooks Moderator Staff Member

    Jul 9, 2009
    Northern CA
    My Coop
    Maybe I should give my chickens my old birth control pills. They are progesterone only. [​IMG]
  6. Overeasyplz

    Overeasyplz Chillin' With My Peeps

    Nov 8, 2009
  7. emys

    emys Chillin' With My Peeps

    Nov 19, 2008
    FireTigeris I know you didn't mean to say feed your chickens avacados. You were just showing us articles. As a disclaimer for you - in case someone reads it that way - there is some speculation as to the poisonous nature of avacados in chickens. It has been shown to be poisonous for other birds.

    (Can't be too safe - at least now we've said it.)

    Cool information everyone!
  8. Benelli

    Benelli Chillin' With My Peeps

    Sep 18, 2009
    Has anyone done studies on egg temps during incubation to get more females vs. males? Birds and reptiles are closer on the genetic scale than most would believe. You can manipulate the temps on snakes and turtles eggs to get more males or females depending upon what you want. It's usually just a matter of 2 degrees to get the results. No, I'm not nuts. I used to raise corn snakes and pythons. Also used to work as a marine turtle specialist and both were proven facts and I've not heard much if anything to the contrary.
  9. Year of the Rooster

    Year of the Rooster Sebright Savvy

    Jun 27, 2008
    West Central Ohio
    Quote:Many people have tried that and discussed it. It is not true for birds no matter how closely related they are to reptiles. Like the article said, it's the chromosomes. This was a very interesting article. Thanks onthespot!
  10. al6517

    al6517 Real Men can Cook

    May 13, 2008
    WOW COOOl, Thanks for the read.


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