Temperature-dependent sex-biased embryo mortality

[bumpercarr]

I've noticed that this year I'm hatching out a lot of cockerels. I'm also having trouble with my incubator holding the correct temperature so I wondered if there was any correlation between the two. Now, I know that many will say that your chances of hatching a cockerel vs a pullet or visa versa is 50/50. Just plain simple, 50/50. As sort of a science junkie, I know that is correct. The eggs should be 50/50, but what about the mortality rate of the embryo in the egg at varying temperatures?

So, I started doing some research and I found two studies (there are probably more, but I don't need to read more than the two) that show that in Turkeys (I'm going to experiment to see if it applies to chickens) that the mortality rate of females is higher when the temps are low in your incubator and that the mortality rate of males is higher when the temps in your incubator are higher. This correlates with what I found with my incubator this year. Since my incubator was having trouble holding a steady temperature, it was frequently cooling by a degree or two almost every day. Hence, more cockerels hatched.

I thought I would share this with anyone who is interested. Maybe they won't have to spend as much time as I did trying to find the research. Latest paper I found is here: http://rspb.royalsocietypublishing.org/content/275/1652/2703.full

You can read the references as well as they give some additional insight.

 

[gamebirdsonly]

Very interesting. I have always wondered that. The last couple years I have hatched 80% of the eggs I have hatched have been Roos and gets frustrating. Now I might know why. Thanks for the Info.

 

[bumpercarr]

Very interesting. I have always wondered that. The last couple years I have hatched 80% of the eggs I have hatched have been Roos and gets frustrating. Now I might know why. Thanks for the Info.

There is one study that I found that say that it doesn't work for chickens, but at this point I'm ready to try almost anything. I'm sitting at about 75% cockerels and it is really beginning to bum me out. If all of my eggs were hatching and this was happening, I would know it was just my bad luck. But I'm having horrible hatches and I know that I have to do something to try to get my pullet ratio up. I have eggs coming again this week and I'm going to give it a try. Hopefully I don't cook everyone, but I'm thinking 100.5F? That way even if my bator starts acting up again it will only cool the normal 99.5 temp. I'll let everyone know in a month how it works out for me.

 

[Lizz9311]

Good luck! I can't wait to see your results!

 

[huntseat]

As a scientist I also read other similar papers and found one that stated the narrow temperature range that a male embryo can actually morph into a female but the female will lay only male eggs. The sex is determined by the hen, unlike many other animals.

I however ran my first hatch too hot, by about 2 degrees F...mostly cockerels. Also had several toe deformities, the far outside toe curls around to varying degrees on about half of the males, this effected none of the female offspring.


http://www.independent.co.uk/news/a-drop-in-temperature-can-change-the-sex-of-chickens-1238516.html

I will say that clearly this must be statistically a draw, because if it worked we would see it in every hatchery, and we don't.

 

[huntseat]

If you find that you are hatching more of one sex than the other, you should be looking at your hens!

I have two that lay only female eggs and two that lay only males. Mark your eggs and keep score you will find something similar in your own flock. You really have to keep eggcellent records but it can be done.

 

[bumpercarr]

I certainly would be looking at my hens if these were my eggs, they are all shipped eggs. My flock was wiped out by neighbor dogs a few months ago and I'm trying to rebuild. That's why the cockerel population is so frustrating. My hatch rate has been atrocious and on top of that they are 75% cockerels (the eggs aren't all coming from the same place either). So, either I am having really horrible luck or I'm killing the female embryos or maybe female eggs don't ship well. But I absolutely agree that if they were my eggs, I'd be trying to figure out which hen(s) were laying so many boys!

I agree that increasing the incubator temperature is a longshot and that if it worked all of the big hatcheries would be doing it. I met a biologist that is a hatchery inspector for Tyson on the airplane about six months ago and picked his brain about their best practices (although I would never, ever run my coop like a hatchery). He did say that there were several things that they did to try to increase the number of certain sexes in their hatches, but most of it was chemical manipulation like hormones. Since I wasn't interested in feeding my chickens hormones, I didn't store in my brain what he told me about which hormones made more of which sex. He also talked about their incubator temperatures, but I think he said their incubators were programmed for different temperatures at different stages of development to increase their hatch rate, I don't think it had anything to do with selecting sex. Anyway, I wish I'd written down what he said.

Good discussion though! I'll let you know if anything comes of this experiment. 4 hatched in March, 2 cockerels (these were the last eggs from my birds) and the two pullets were eaten by some neighborhood cats, they couldn't have gone for the cockerels? Then my incubator started losing a degree about every other day, wouldn't hold at the set temperature. It took me a while to figure out what was going on with the incubator, it seems that I have 4 thermometers that all read a significantly different temp. In the meantime, I already had eggs on the way so I had to try to hatch them by watching it carefully. So, as I'd go to bed at night, it would be holding steady at 99.5. In the morning, it would be down to 98 and I wouldn't have any idea how long it had been that low. It took me until halfway through my May hatch to get it to hold the correct temperature (replaced the controller) and figured out which thermometer is actually calibrated. I had 8 hatch in my April batch and 6 cockerels. 4 hatched in my May batch, 3 are cockerels (I think). I'll set these at a little bit higher temp and see if it improves my ratio any.

At least I know that my freezer will be full this fall!

 

[huntseat]

Low temps should give a nod to the female chicks, high temps increase males. Based on turkey data which trends with my own experiences.

Once you get a good hen that lays female eggs you will off to the races.

I wonder if the people selling hatching eggs aren't shipping the eggs from hens they know to lay more males eggs...my gut says that's exactly what's happening.

 

[bumpercarr]

Low temps should give a nod to the female chicks, high temps increase males. Based on turkey data which trends with my own experiences.

Once you get a good hen that lays female eggs you will off to the races.

I wonder if the people selling hatching eggs aren't shipping the eggs from hens they know to lay more males eggs...my gut says that's exactly what's happening.

I hope not! I've worked really hard to find respectable breeders for the birds that I want to raise. When I decided to focus on one particular breed, I researched and bought from these same breeders and had about a 50% hatch rate and close to 50/50 sex ratio (hatched 3 batches, think I had one cockerel over 50/50). I started hatching my own eggs this season in December, still had about a 50/50 sex ratio. Set some shipped eggs in January, 40% hatch rate, 50/50 sex ratio. Everybody killed (except two pullets who were very badly injured) in February, hatched the last 6 eggs from them (4 hatched) with a 50/50 sex ratio. And then everything went to pot I think because of incubator problems. Hatch rate at its worse was 5%, sex ratio was 75/25. But just in case you are right (believe me, I've wondered the same thing) I bought from a different breeder this time.

Being of a scientific mind, I really feel like I'm changing the control group by switching breeders, but I just want to make sure that something hasn't changed in my preferred breeder's flock that is causing these problems. It is also good to have some genetic diversity, but I feel like I'm messing with my formula and thus won't be able to conclude positively whether my hatch rate and sex ratio is in the incubator or in the hens (sex ratio dependent on the hens, not the hatch rate) or in shipping methods. Unfortunately, any of the experimentation that I was trying to do got blown away when the flock was decimated. I'm getting a replacement incubator this fall, I just don't trust this one anymore even though I've fixed the problem. So, next season I will be able to truly conduct some experiments with my own hens and maybe be able to put my finger on whether this is an old wives tale or whether there is a statistically significant difference in the sex ratios.

So, for this batch (my last batch until I can get my own eggs) you think I should turn it down a bit? I've really got to get some pullets, I'm overrun with cockerels right now. Seems like even when I hatch pullets, some predator comes and takes them instead of the darned cockerels. If I can't increase my pullet population, I'll have to travel pretty far to try to buy some juvenile pullets to breed. I think the closest breeders that have what I want are either in Oregon or Wisconsin. There might be one in Missouri but I've never had any contact with him. I suspect I'll have plenty of cockerels to chose the best to breed from.

 

[abserbean]

Very interesting discussion! I was told before by a vet that temp would affect the sex of hatches, but I don't have any experience doing it myself. Maybe the hatcheries are doing this? It wouldn't be 100%, so they would still have cockerels.I hatch with a broody, so no control over temp/humidity. I have heard of people getting 80-90% pullet or cockerel hatches using a broody, maybe different hens have different hatch rates? Our spring hatch was 7 out of 9 eggs, with only 1 confirmed cockerel so far. Very curious.