The mess left behind by broken eggs is
an obvious reason for you to care about the shell quality of
the eggs laid by your hens. A less visible reason is the
higher level of salmonella found in cracked compared to
intact eggs – especially if they are improperly washed.
The most common causes of weak shells
eggs in your flock are:
- Old Hens – Shell strength declines
steadily as hens get older. If you buy old hens from a
commercial farm, they are already well past their prime
for shell quality.
- Calcium Deficiency – To supply the
calcium needed to make good shells, 10% of the feed must
be supplied as limestone or oyster shell. For birds in
floor pens, a hanging feeder of limestone or oyster
shell can be used as the calcium source. When a layer
diet is used as the sole source of calcium, restricted
feed consumption due to crowding and other problems can
also restrict calcium intake.
- Poor Calcium Sources – Insoluble
granite grit and egg shells are poor sources.
- Excess Phosphorous – Too much
phosphorous in the diet will decrease shell thickness.
If you make your own feed, carefully weigh out the
amount of mineral phosphorous.
- Early Production – Hens that begin
egg production before you get them on a good layer diet
can rapidly deplete their bone reserves of calcium.
- High Temperature – Temperature
stresses the hens and reduces shell strength.
- Vitamin D3 Deficiency –
Hens need a commercial source of vitamin D3
in the feed. Deficiency is most visible in the winter
months when the birds get less sunlight and make less
vitamin D3 on their own.
- Infectious Bronchitis – This virus
readily attacks the shell gland of unvaccinated birds.
- Excitable Hens – Hens that are
excited may produce thin or poorly constructed shells.
Less common problems include
insufficient manganese in the feed, toxins or pesticides,
and miscellaneous diseases such as coccidiosis and
Infectious Laryngotracheitis (ILT).
Shell quality can be improved by
providing the nutrients needed for the hen to build her bone
reserves of calcium and make good shells:
- Feed a third to half of the
calcium as large particles that are approximately ½ cm
in size. Both oyster shell and limestone the size of
small pebbles will last longer in the gizzard and supply
calcium at night when the hen makes the shell.
- Supply a pre-lay diet containing
2% calcium for the two weeks prior to the start of egg
production. Due to hormonal changes as the birds ready
for egg production, they are able to use the extra
calcium to build up their bone reserves. A hanging
feeder of limestone or oyster shell is another way to
give the birds access to the calcium they need.
- Switch the flock immediately to a
laying diet which has 3.5% or more calcium when you see
the first egg laid by the flock. Approximately 10% of
the diet must be limestone or oyster shell to provide
this much calcium
- Let the hens will pick limestone
or oyster shell as they need it from a hanging feeder.
See the MAFRI web page on choice feeding.
- Give vitamin D3 in the
water one day a week. Follow the package instruction and
do not add more vitamin D3 than recommended.
- Keep your birds calm. Do not give
them more than 16 hours of daylight. Letting them sleep
longer will keep them calm during the time of day when
they are forming the shell.
These practices will not stop the
natural weakening of the shells as your hens age but will
help to prevent any premature problems. If your old hens go
into a moult, shell thickness will be temporarily improved.
Weak Shells can lead to cracks & "Leakers"/
Photo- University of Georgia Cooperative Extension