Why do Wattles Shrink?

[SwtGrc]

Good question and good guesses. It has nothing to do with temperature. It does have to do with egg laying. However the reason is that it is related to day length or, more accurately, whether days are getting shorter or lengthening.
It just happens to be cold when days are short in most climates.

Here's a brief rundown of the science.
Light exposure to the retina is first relayed to the nucleus of the hypothalamus, an area of the brain that coordinates biological clock signals. Fibers from there descend to the spinal cord and then project to the superior cervical ganglia, from which neurons ascend back to the pineal gland. The pineal gland translates signals from the nervous system into a hormonal signal.

When light periods are shorter, the gland produces serotonin and subsequently, melatonin. That's the hormone that affects the gonads for sperm production in males and ovulation in females. An increase in melatonin causes the gonads to become inactive. This also causes combs and wattles to pale and shrink.
Photoperiod, in relation to day vs. night, is the most important clue for animals to determine season. And by extension, when to reproduce.
Cold really has very little to do with egg production. The same thing happens whether it is a cold or warm climate.
As light lengthens, the gonads are rejuvenated. The duration of melatonin secretion each day is directly proportional to the length of the night because of the pineal gland's ability to measure daylength. Besides reproduction, it also affects sleep timing and blood pressure regulation.
So as the light period increases, in relation to the dark period, it stimulates reproduction, the growing and reddening of combs/wattles - voila - EGGS.

This is great info , however in my case, only one of my Hens seems to be affected by this. She was the first to start laying at 16 weeks and the only one to stop laying completely. (She's 8 mo now)
Why would this be??

 

[oldhenlikesdogs]

Combs are a visual sign of reproduction. They generally shrink due to decreased hormones and enlarge when hormones surge. Roosters combs don't shrink back like hens do because most roosters are always fertile where hens go out of lay. Hens with shrunken combs are generally not laying, thus the rooster won't mate them based on comb color and size.

 

[Little Chicken Girl]

Good question and good guesses. It has nothing to do with temperature. It does have to do with egg laying. However the reason is that it is related to day length or, more accurately, whether days are getting shorter or lengthening.
It just happens to be cold when days are short in most climates.

Here's a brief rundown of the science.
Light exposure to the retina is first relayed to the nucleus of the hypothalamus, an area of the brain that coordinates biological clock signals. Fibers from there descend to the spinal cord and then project to the superior cervical ganglia, from which neurons ascend back to the pineal gland. The pineal gland translates signals from the nervous system into a hormonal signal.

When light periods are shorter, the gland produces serotonin and subsequently, melatonin. That's the hormone that affects the gonads for sperm production in males and ovulation in females. An increase in melatonin causes the gonads to become inactive. This also causes combs and wattles to pale and shrink.
Photoperiod, in relation to day vs. night, is the most important clue for animals to determine season. And by extension, when to reproduce.
Cold really has very little to do with egg production. The same thing happens whether it is a cold or warm climate.
As light lengthens, the gonads are rejuvenated. The duration of melatonin secretion each day is directly proportional to the length of the night because of the pineal gland's ability to measure daylength. Besides reproduction, it also affects sleep timing and blood pressure regulation.
So as the light period increases, in relation to the dark period, it stimulates reproduction, the growing and reddening of combs/wattles - voila - EGGS.

I just encountered some new information on this subject that might be of interest. A study was done by Guelph University (Canada) on chickens with genetic defects that cause them to hatch with no retina. These chickens reproductive cycles where completely functional (which would not be possible given that the light sensed by the retina is what effected reproductive cycles). Dr Petrik (a poultry vet) says that light is sensed directly by the pineal gland. This is possible because the pineal gland being located under a thin section of skull located in between the bird's eyes. You can read more about it here : http://www.the-chicken-chick.com/2011/09/supplemental-light-in-coop-why-how/

 

[ChickenCanoe]

You're right about that. Even blind chickens can sense day length due to light penetration of the skull.

 

[aart]

Yeppers!