DNA results

[gomer]

I cant believe the last two batches i sent in to get dna'ed in the last month. Thirty samples in total twenty three hen birds and seven cocks.Both batches have been done twice due to the unusually high number of hens to double check.I also have had a unusual high amount of hens in the diomorphic birds aswell this year. I have heard diet can control sex at egg stage ? Has anyone else heard this or is anyone else experiened a high number of hens from last season.

[vettepilot_6]

I think it is partially diet and weather combined...wet years I seem to get more hens...

[Greg41]

I don't keep a large number of finches but recently had 7 strawberry and 10 rfpf young dna'd , 6 hen strawberry and 5 of each rfpf.
A good result for me.

Cheers Greg.

[BrettB]

I have not seen any data on diet influencing sex ratios, but would love to hear if anyone has.

It does appear that the stress hormone corticosterone may have a role though.
I wrote this little tongue in cheek article last year.

Too many Cock birds? Bad Luck or Bad Management

You do not need to talk with too many finch enthusiasts before you will hear a story about unequal sex distribution. There was that clutch that produced 5 chicks, all cock birds, or another that produced 4 hens. I have always assumed it was a question of luck, but there may be another explanation.

Sarah Pryke, well known for her scientific work on Gouldian finches, published a study in 2013 titled “Experimental evidence that maternal corticosterone controls adaptive offspring sex ratios”, quite a mouthful. Put simply, does the stress hormone corticosterone affect the sex of chicks. Her study showed, that at least in the Gouldian finch, it does. Hens with high corticosterone levels produced up to 80 % cock birds while hens with low levels produced only 20-30% cocks.

How the study was conducted is interesting. She actually used small implants that contained either the hormone corticosterone or metyrapone (a drug that lowers corticosterone levels). The implants were inserted on the first day of nest building. The pairs were allowed to breed for two clutches and the alternate drug was used for the second clutch. Only red headed birds were used, but some of the males had their heads dyed black so they looked like black heads. (this relates to some of Sarah's other work on “incompatible” head colors)

So what is going on here and how can it happen? In humans males carry the Y chromosome that determines sex. All of the ovum (eggs) carry X chromosomes. XX are girls and XY boys. Birds are different with the sex determining chromosome being carried by the hens, hens are WZ and cockbirds ZZ. Consequently it is the ovum (eggs) that determine the sex, not the sperm. This leave room for some manipulation by the hen to influence the sex of the chicks, by influencing which ovum progress, although the mechanism for this remains unknown. It would appear from Sarah's work that the stress hormone, corticosterone, plays some part in this.

So lets leave the sciency stuff aside for a moment and consider the implications. If high corticosterone levels increase the proportion of cock birds produced, then how can we influence that? In Gouldians, higher corticosterone levels have been associated with over crowding, aggression, poor nutrition, prolonged handling and poor quality partner. It is likely that any “stress” will similarly cause it to be increased. Likewise reversing these would result in a fall in corticosterone levels and an increased proportion of hens being produced. I see a new age on the horizon where the discussion is not about green seed, live food and sprouts, but around strategies to reduce the stress on our hens.
Perhaps we will be playing classical music, using aromatherapy and installing spa baths and foot massages for our birds !!

Maybe your birds are too chilled Derek

Cheers
Brett

[shnapper20]

I believe its the weather, some years way more hens then cocks, other years the other way around. Talking to other breeders they have experienced the same thing for that particular year. At least this was the case with my gouldians.

[MuzzaD]

An interesting discussion. Stress definitely has an impact and food stress controls a lot of factors.
Not always lack of feed but variety, balance and quality play a part.
A stock agent told me that in the north of WA during dry years more feral male goats were born and reverse in good years. This helped control breeding patterns for future years. Obviously based on natural food production. There was also a study into human reproduction looking at alkaline or acidic conditions where some transmittable problems could possibly be avoided.
When I bred angora goats I had a relatively small kikuyu grass area that was irrigated and fertilised. The does went on there for two weeks approx before the buck was introduced. Always had a higher percentage of does to bucks born. This was often opposite to the wheat belt studs results.
The study into Zebra finch compatibility through selection their own mate was also interesting in the fact that it also played a big part in mothering and percentage of live offspring.
No answers here but agreeing that the environment is important in many ways.

[Masterfincher]

I was just looking at my gouldian young from last year; a bit over 2/3 are hens, both black and red headed. I did focus on providing plenty of nesting and food variety, and i don't feel they got stressed much at all, so there could be something to this.

[Curly]

Hi all, who & where do you get DNA testing done
I have some young Diamonds that I want to get done
thanks for your help
Cheers Brice

[gomer]

Curtin University in W.A I use.

[E Orix]

David Groth from Curtin has a new email address

[email protected] If this fails send me a pm

It is a simple process, pull 2 tail feathers out including the quill end
place them in a small plastic sealable bag, put in a reference ring colour etc and
specie.
Only one set of feathers per bag and make sure all ring colours are different
numbered ring are better
Cost around $10 per bird and don't forget to give him your email address it's
quicker and cheaper.