How to hatch more females?

[OLIVEandMURPHY]

I have a pair of Swedish/Cayuga ducks that will be hatching their second clutch in about a month. Last spring my female hatched 11 eggs out of 12, and almost all of them were male! I read somewhere that certain temperatures can influence the sex of the eggs in early growth stages. What temperature should I keep the eggs at if I want to hatch more females than males?

Thanks!

 

[dheltzel]

What you're describing has been thoroughly documented in reptiles (along with parthenogenisis - "virgin birth"), but never in birds. Reptiles lack a chromosome-based sex determination (as do fish). Birds and mammals have sex chromosomes, allowing us and chickens to have sex-linked traits (color blindness and hemophilia are sex linked in people, barring is an example in chickens).

The result of this is that there is no way to change a male to a female, every egg is by definition male or female (interestingly even an unfertilized egg has a gender in the chromosomal sense, unlike humans where sperm can be considered male or female).

The best you could hope for is that temperatures might kill more males than females if manipulated in certain ways, but everything I've read seems to indicate that the females die before the males, so manipulating temps is more likely to result in a way to increase the number of males over females, not what we are looking for.

If you hear there is some magic way to change the sex of a chick, consider this - if it were at all feasible, don't you think the hatcheries would be all over that research? They would gladly fund promising research if it meant they would not have to hatch (and dispatch) millions of male chicks.

Even if we could find a way to determine the sex of an egg before setting it, that would be huge because we could just eat the male eggs and hatcheries could literally cut most of their costs by half !!

Incidentally, the dairy industry has been the recipient of this sort of thing, You can now get "sexed semen" that dramatically increases the odds of getting a female calf. It's expensive, but usually worth it because of the economics of that industry. I'm sure poultry researchers, who know a lot more about this stuff than I ever will, have given this idea of sexing eggs or getting hens to lay disproportionate numbers of female eggs, a lot of thought.

 

[WalnutHill]

"Storey's Guide to Raising Turkeys" has an anecdotal tale in the incubation chapter.

Quote:
Sex of poultry is indeed determined by the egg, not the sperm that fertilizes it. So you can perhaps influence success or failure of a particular sex, but you can't change it. Not with home methods, anyhow.