Fascinating Research On Testosterone Variation Within Chicks Of The Same Clutch
Dr. Hubert Schwabl, a German scientist working at the Rockefeller University Field Research Center in Millbrook, N. Y., discovered that the canary hen doles out the vital hormone testosterone in carefully tailored inequitable amounts that gradually increase from the first to the last egg laid.
While the egg is developing inside the hen, she adds, in addition to the standard accretion of protein, fat and nutrients a lacing of testosterone, the male hormone. Dr. Schwabl discovered the the hen donates the testosterone to her eggs early in their development, while they are swelling up from the follicles surrounding her ovaries but before they have been inseminated by a male's sperm. During that rapid egg production, a layer of cells is laid down around the egg yolk able to produce testosterone. Later, during incubation, as the chicks bloom within the shelter of the shell, the testosterone seeps through the yolk and enters their bloodstream.
If eggs are not removed daily as laid, the asymmetry of hatching creates a huge size disadvantage for the last chick hatched. To help level the playing field, each egg in succession is given a tailored larger amount of testosterone to create an advantage over the previous chick. In fact the amount of testosterone in the fifth egg is 20 times that given to the first egg! She does this without regard to whether the recipient is a he or she chick, but rather to lend a head start on their development.
Testosterone is well recognized by body builders and football players as a source of strength, stamina, and surliness. For canaries, testosterone increases begging, body mass, growth rate, and aggression. Chicks that fail to beg will not get fed. If they don't beg their parents will ignore them and they will die.
Chicks hatching from the last egg laid, regardless of whether they are male or female are the most aggressive! Testosterone may also play a role in the maturation of the spinal cord, allowing the chicks to coordinate their movements, lift their heads and demand their dinner.
I found this research very helpful as I always wondered why some chicks were so aggressive and how the growth rates within a clutch were so uneven. I have long known that animal protein in the diet promotes aggression but even then there was variation amongst chicks of the same clutch! I also had observed that chick vents appear somewhat male-like even when barely feathered but of course they can't be all cocks!
Lesson: Not all Canary Chicks are Created Equal, it's true, but you can help equalize the playing field too by removing the eggs as laid!
Be Sure and Read The Comments to this Post!
Mary I have a Q for you. I have a stafford hen who is in prime breeding form but the male bird that I'm getting is near moult stage. Now! how long should I wait before I try and breed them after he moults??
Sorry Linda I called you Mary in my last post, I had just got finished talking to my friend called Mary. Doh!!
Brian in Savannah
After the molt, it will be a long time (many months) before the cock is in full breeding condition.
I recommend that instead you get him promptly and get him started on the ABBA water soluble vitamin E. It is put in the water and given as the only water for 24 hours once a week. Using this product, I have had cocks fill all the eggs and chicks hatch when the cock is clearly molting on the wing butts!
This is a fascinating article and I think it creates more questions to be thought about. Although I also take away eggs each morning, I think that this year it may be difficult as I will need to leave home before the hens finish laying. I am wondering what an effect it really has on the youngsters and how much the disadvantage really is. I mean mother nature ensures that enough testosterone is deposited in the egg so that the last youngster is able to compete equally for food then surely this design should be nature's way of ensuring a fair starting ground for the youngsters?
I am going to try not taking eggs away from a few pairs just to see the difference.
I think sometimes we do all kinds of things like take the eggs away and possibly create alot of our own misery.
Possibly taking the eggs away increases risks such as drying out of the egg, contamination etc and in so doing affects the hatchability of the embryos. Also by giving everyone "a fair chance" we are possibly going against natures rule of survival of the fittest?? Your ideas M'am?
Please tell me how things are going with the colony breeding experiment? Really excited about the prospects.
Numerous factors effect survival of chicks but perhaps the greatest is when a chick hatches in relation to when the siblings hatched and the number of chicks in the nest. The less chicks in the nest, the easier a late hatch can cope with the size difference. So if you expect a couple per nest, you could leave the eggs in but don't do it if you expect four or more.
Some hens helps out some by not reaching full incubation temperature immediately.
Scientific studies (Cutler BA, Abbott, UK) on cockatiel eggs showed that their eggs could be incubated for two days and then stored at 55F to 75F at 60% relative humidity without decreased hatchability until after three or four days of storage.
I would recommend that if you can't remove eggs in the early morning to remove them in the evening and set hens in the evening.
The liquid calcium is absolutely critical to borders!! Their intestional absorption of calcium in many hens is so poor that the chicks dry out. Humidity is the other factor and I am not sure what you relative humidity runs but the two factors, shell thickness and low humidity are killers!
I have had a mixed breeding season. A couple of things happened which I learned a great deal from. I always hold back till spring rains for breeding and I held off till they were predicted but they didn't come till much later.
The company that I usually bought my liquid calcium from went out of business and although I have used liquid calcium every season for probably twenty years, I thought that if I started at least three months ahead really pushing egg shell and digestible grit, it would be equivalent. Wrong, it was ok for staffords and colorbred, they produced great eggs but mixed on the rollers but horrible quality on the border eggs.
It broke my heart to have nests of six fertile border eggs only to find the shell had dried out and they couldn't be hatched or in some cases the eggs would dent as they were hatching resulting in the embryo being smashed inside the egg while trying to hatch! Never had I seen this in any of my birds in all the years of breeding! The lesson was clear. Production was directly correlated with better shell quality and with borders and rollers you had better do that with liquid calcium with the right amount of D3!
The colony breeding aspect of breeding borders went well. The border hens temperment was so good. In some cases, they preferred to nest side by side in a long flight and in one case one is sitting on eggs while the other is feeding and their nests are side by side in a larger flight. Cocks that did not fill eggs in a colony were tried in a single pairing and they failed there also. I will continue to colony breed borders next year.
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