temp and sex

i knew I had just read something on this..... found this - A study in Australia (Australian Journal of Agricultural Research 11(4) 664 - 672) has shown that eggs stored at 40 degrees Fahrenheit (rather than the recommended 60 degrees) hatch out more females than males. However storing your eggs at colder temperatures before hatching doesn't actually change the ratio of male to female eggs. It has been shown that the male embryos are preferentially killed off by colder storage temperatures, while the female embryos handle the chilling better.

Chicken sex chromosomes are Z and W. Somewhat like the X and Y chromosome in humans. The difference is that in humans the female is XX and the XY chromosomes of the male determine the sex of the child. If the haploid sperm gamete the does the fertilization contains the X chromosome the the child will be a female. If it contains the Y chromosome, then the child will be male. In chickens the male sex chromosome is ZZ and the female is ZW. Therefore it is the female chromosomes that determines the sex of the chick. The process of meiosis produces four Haploid sperm cells each containing one Z chromosome whereas I the female meiosis produces four haploid cells. Two with the Z chromosome and two with the W chromosome. Of these four only one survives with a 50/50 chance of it being a Z or W chromosome. These means that half the eggs produced by the hen will have the female producing W chromosome and half will contain the male producing Z chromosome. Once fertilization occurs the sex of the chick is imediately determined. Any variation of temperature, during incubation, would only lead to more Roos or hens, if a higher or lower temperature lead to the demise of one sex or the other. In other words, if female chick are more susceptible to death at higher temperatures then you will have a higher percentage of males because the embryos that don't develop or die before hatching would mostly be females. If them male chicks are more susceptible to death at lower temps then you will have more hens at lower incubation temps because those that don't hatch would more likely be males. (I don't know this to be the case but that might explain the discrepancy in the ratios of chicks. If one were to have an unheard of 100% hatch rate the ratio will be approximately 50/50. Hope that helps

Mrs. K said:

Several years ago, on the hatching and raising page, people put in for nearly a year, how many eggs they sat, and how many hatched. One added it to the totals above, and divided. At first as all statistics do, the percentages varied wildly, but over time, they began to average and there became much smaller swings.

It came very close to a 50% hatch rate. If you have been hatching eggs long, most of us have had a poor hatch or two, and sometimes a perfect 100% hatch. I have found that hatching smaller hatches actually gives me more chicks, but any hatch above 50% I consider a win. This was true under broody's or incubators.

All I am saying, while not perfect, one could easily set up a test to see if the shape was indicative as to the sex of the bird.

As a side note, even with the 50/50% that is should be, we have all known families were it did not follow the punnet square of probability. Ken had a cow that he liked very much, and she raised beautiful heifer calves, and he kept every one of them, as they too were good cows. She did not have a bull calf until her 10th calf.

It is a crazy hobby. If you are going to go dual purpose, eggs and meat, I do recommend upgrading to a higher quality rooster, getting a new one every two years. It does make quite a difference in the quality of meat. And getting a drill mounted plucker, it makes harvesting the birds so much easier!

Mrs K

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Thank you Mrs. K! I was wondering this this morning and "poof" there you are with the answers. I got thinking about the 50/50 and how many folks tell me it is more 70/30 in their experience. I was thinking it was just that those folks are hatching 6 at a time where I am hatching 20+ Hopefully my hen / roo ratio will be close to normal I'd really like having 10 females on the first hatch!

Jacqueline - I think we are talking at cross purposes. In the post above, I was talking about the number of live chicks out of eggs hatched, not female to male ratio.

As for getting 10 hens out of 20 eggs, you might, but you might not. Only thing to do is wait and see. If you were hatching 500 eggs or better 1000, then I would pretty confidently say, you would get fairly close to 50% females to 50% male, perhaps with a slightly more males. However, last year, I hatched a dozen live chicks, and 9, yes NINE were roosters! That is the way it goes.

you are right of course. I guess 20 is not enough! Seems like a lot to me

Mrs. K said:

Jacqueline - I think we are talking at cross purposes. In the post above, I was talking about the number of live chicks out of eggs hatched, not female to male ratio.

As for getting 10 hens out of 20 eggs, you might, but you might not. Only thing to do is wait and see. If you were hatching 500 eggs or better 1000, then I would pretty confidently say, you would get fairly close to 50% females to 50% male, perhaps with a slightly more males. However, last year, I hatched a dozen live chicks, and 9, yes NINE were roosters! That is the way it goes.

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Two years ago I hatched a dozen Spitzhauben. 10 Roos and 2 girls! Last year I did a dozen silkies. 4 Roos and 8 pullets. Lol
Now on my hatches of 20-40 with my standard birds, it was much more even, sometimes more favorable to the hens others to the Roos, but more even.

It's just odds. I normally hatch about 20 chicks per hatch in the incubator, plus or minus a few. I very seldom get that close to 50-50 each hatch. For example, this past January I hatched 21 chicks. 8 so pullets so 13 are male. Another hatch before that was 14 pullets and 7 males. I had one hatch last year 14 pullets and 5 males. Sometimes I do get a hatch really close to 50-50, but not that often.

Something I have noticed. Several times I've added up all the chicks I've hatched over a two year period, usually just over 80 chicks total, some under a broody and some in the incubator. It's always added up to within one or two chicks of 50-50, even with some individual hatches really skewed.

I wish you luck on getting mostly pullets. About half the time you get as many or more pullets than males. That's not horrible odds.

Last night as i went in to check on them 7 were standing up right watching me. I understand boys are more likely to behave this way. I dreamt i had 14 hens. That would be a bit of a worry just now since I only have over winter space set up for 9. I was expecting somewhere between 4 and 7 hens with 20 eggs. We shall see, the difference between comb development between Icelandic (no development at 10 days) and Marans which are developing noticeably is incredible!

I am quite sure its NO.temperature affects outcome in reptiles but not birds.






























http://www.soran.edu.iq

dheltzel said:

Reptiles don't have sex chromosomes, that is why some are temperature determined genders, also why there are no sex-linked traits in reptiles. The sex in mammals and birds is determined by sex chromosomes, so they sex is determined at conception, and also there are documented sex linked traits in many species.

The best you could hope for in manipulating the incubation temps is the preferential killing of a certain gender that might be less tolerant of temp extremes, not a useful outcome in my opinion.

Egg shape is also a lost cause. Consider this -- if there were anything to it, the commercial hatcheries would be all over this, the potential cost savings there are huge, imagine if they only needed to set half the number of eggs (or get twice as many pullets) in their expensive equipment. The layer industry would gladly fund any research that had a chance of finding a way to sort eggs by sex.

They did finally (at great cost for R&D) develop a process to sort the semen from bulls so that a far higher percentage of females are produced for the dairy industry. That "sexed semen" is much more expensive, but still used a lot by dairy farmers. Sorting eggs would be a similar challenge, with millions of dollars at stake for the lucky company the finds a way to do it.

So, I really doubt that old wives tales about egg shape.

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I do see quite an imbalance is sex ratio for some breeds. If not the incubator temperature, could it be determined by the specific blood line? I was a working scientist for many years, do you know of relevant scientific studies. If so, I would be happy to read them, and relate the gist of the articles in layman terms for all of us to read.