IS SHELL IN BORDER BREEDING: SOME THOUGHTS….
Dead in shell (DIS) in
Border breeding rooms has become an apparent and not yet solved problem. By DIS we are speaking
of a fully developed chick unable to pipe the egg.As the exact mechanism
behind this has yet to be solved, we might reflect on some thoughts about this
First of all some
breeders don’t have this problem, so I would say, never change a winning team,
as because you don’t know exactly what you are doing right, things seem to go
well. But, it could be you are using
birds with another genetic background as to others, might be a cause.
One of the main causes
has to be found in eggshell structure, read: something is wrong with it.
The main constituent
of the eggshell is calcium, so maybe there is something wrong with the calcium
metabolism? If the hen does not get enough calcium on eggshell formation,
eggshells might be thinner. Now, here is the delicate balance on this. If
eggshells are thin, the pores in the eggshell are bigger from the day the hen
lays this egg. If you pull the egg and store them till the day the fourth egg
deshydratation of the egg can start right away. So, when eggs are stored we
have to be sure humidity in the breeding room is already around 55° RH. During
the incubation of the eggs the chick inside of it is using calcium from the
eggshell for development and in this way the pores do get bigger during
incubation. In this way, the egg undergoes deshydratation and the chick gets
stuck to the egg membranes. Another thing to watch for is when storing the eggs
you put them “small end up”, as in this way the contact surface for possible
deshydratation diminishes. Also, for this period of 3 to 4 days, there is no
need for turning the eggs. So, humidity is a key
factor thinking about us breeding birds who sometimes do have a problem with incorrect
eggshell formation., and the right balance of eggshell thickness and humidity
is a major factor.
Also remember the
pores in the eggshell have another function: respiration! Through these tiny
holes oxygen is taken up and carbon dioxide is eliminated. So, keep the shed
well ventilated, all year round.
On the other hand if
eggshells are too thick by incorrect use of megadose of calcium and vitamin D
the eggshell becomes too thick, by which a normal loss of weight of about 15%
can not take place, and the chick drowns in the egg fluid.
Calcium, or lack of
calcium seems to be the main cause in faulty eggshell structure. Calcium needs
increase while breeding but as we all offer cuttlefish bones and some mixed
mineral supplement, it seems we do things right, which is correct. So, there
has to be some problem with the calcium not getting where it has to be. We all
know calcium is absorbed in the intestines under the influence of vitamin D. But
vitamin D, before becoming the active form of vitamin D, has to be transformed
twice after absorption before being active. The first activation is done by the
liver giving rise to 25 OH-Vitamin D, after which a second activation occurs in
the kidneys giving the active form of vitamin D, the 1-25 OH Vitamin D3.
So, if thinking about
this, there might be a problem in the liver , this can be due to infectious
disease (latent atoxoplasmosis), nutritious (fatty liver syndrome) or genetic,
by which I mean breeding birds who have a genetic defect of the enzyme in the
Another cause could be
the kidneys, if kidney function is impaired enzymatic function decreases, for
example by giving too much calcium in the drinking water, or, again, some
genetic enzymatic inherited problem of kidney enzyme activity.
Calcium being given in
the drinking water is one of the things often being done by fanciers with
success. By doing this the route of vitamin D dependent calcium absorption is
being bypassed and the calcium is absorbed through passive diffusion in the
intestines, no need for vitamin D! But, if overdone, as already mentioned can
lead to kidney stones and impaired kidney function with impaired vitamin D
Another aspect is the
chick, when piping the egg needs calcium for muscle contraction when piping the
egg and turning around on itself. Also this chick, albeit possible getting the
calcium needed from the eggshell, also needs vitamin D. Vitamin D is being
stored in the egg as the 25 OH vitamin D, and this is activated by the chick
when calcium is needed for piping. So, even if you get good eggshell quality by
giving calcium supplements, it might be possible you have not met the chicks vitamin D levels in the
egg. In poultry breeding 25 OH vitamin D
is being used as well as for getting better eggshells and as we know by now,
the necessary 25 OH vitamin D3 levels stored in the egg, so the chick can
activate this when it needs calcium for muscle contraction.
Also of importance is
the energy source the chick uses when piping the egg, which is mainly energy
from fatty acids. It has been shown when supplementing the hens food with the
necessary antioxidants, these fatty acids are not broken down during the
incubation period and the chick can use them as the main energy source when
piping. In these antioxidants we think about vitamin A, vitamin C, selenium,
vitamin E, carotenes and glutathione, as we can find them in fruits, vegetables
and spirulina. One can also increase the amount of “good” fatty acids in the egg
by supplementing the hens diet with some brewery by products which do contain
have been mentioned by some, like Mycoplasm infections, but till today nobody
has been giving feedback the problem has been solved by a prebreeding cure of
tylosin or tiamulin. I am sure many have been trying this, so reports should
give us some more insight in this.
So, by now we have:
between eggshell thickness and ambient humidity.
vitamin D dependant and not vitamin D dependant.
source for the chick when piping, fatty acids, and the protective role of
antioxidants in this.
and 25 OH needs of the piping chick for muscle action.
cause? No positive reports on this yet.
errors in metabolism in some strains?
For as it is by now, a
single main cause of DIS has not yet been found, it is my opinion the causes
are multifactorial and the way to solve this problem is by reporting as well
some positive effects of some action being taken, as well as the opposite, we
all can learn from both sides of the story. I know the Border Convention is
taking all this under its wings, but I think more feedback is needed.
Dr Jan Vanderborght MD