International Journal of Zoology Studies
International Journal of Zoology Studies
Impact Factor: RJIF 5.14
Volume 3; Issue 4; July 2018; Page No. 31-33
Comparative study on calcium content in egg shells of different birds
Shwetha A1*, Dhananjaya2, Shravana Kumara SM3, Ananda4
1-4 Department of PG Studies and Research in Applied Zoology, Jnana Sahyadri, Kuvempu University, Shimoga, Karnataka, India
This study was designed to evaluate the calcium carbonate in different birds’ eggshell because it has a potential application in the
development of a new option of pharmaceutical excipient. Egg shells are the rich source of mineral salts, mainly calcium
carbonate, which is probably the best natural source of calcium and it is about 90% absorbable. The composition of the egg shell is
approximately 98.2, 0.9, 0.9% Calcium carbonate, Magnesium and Phosphorous (phosphate) respectively. Discarded eggshells are
often used as a plant fertilizer and are effective liming sources. This is because eggshells contain calcium that raises, or neutralizes,
the pH level in surface layer of acidic soils. In the present study, the highest Calcium content was determined in the eggshell of
lapwing (96.46%) and hybrid hen (95.28%), this was followed by duck and Pigeon and least in the Swift eggshell (68.06%).
Chicken eggshells can be used as an alternative soil stabilizer like lime since they have the same chemical composition. The
multiple uses of eggshells in nutrition and medicine and can be utilized for various purposes that minimize their effect on
Keywords: eggshell, calcium, weight and percentage, birds
Calcium is a vital component of a healthy diet and a mineral
necessary for life, particularly in cell physiology where
movement of the calcium ion in and out of the cytoplasm
functions as a signal for many cellular processes. The amount
of calcium in the body depends on the amount of calcium you
get in your food. Eggshells are waste materials from
hatcheries, homes and fast food industries (Bain, 1997; Nys,
2004,) [3, 9] and can be readily collected in plenty. Eggshell
waste disposal contributes to environmental pollution.
Challenges associated with disposal of eggshells include cost,
availability of disposal sites, odour, flies and abrasiveness
(Amu et al., 2005) .
Eggshell is non-edible by-product with little saleable value but
they may contain biologically active compounds (Nakano et
al., 2003) . Calcium is the major component in an eggshell.
There is also a small amount of magnesium in the eggshell
and trace amounts of other micro elements. Eggshell calcium
is the best natural source of calcium and it is about 90%
absorbable, than limestone or coral sources. The whole
medium eggshell makes about one teaspoon of powder
(Nakano et al., 2003; Kingori, 2011) [8, 7]. Birds lay hard-
shelled eggs, most birds’ eggs are incubated in nests and are
often highly conspicuous, so their colour serves as
camouflage. However, the shells are porous enough to allow
oxygen to enter the egg and carbon dioxide to leave. The shell
and the albumen (egg white) protect and cushion the
developing embryo. The albumen is also a source of protein
and water for the embryo (Adeyeye, 2009) .
The composition of the egg shell is approximately 98.2, 0.9,
0.9% Calcium carbonate, Magnesium and Phosphorous
(phosphate) respectively. One whole medium sized eggshell
makes about one teaspoon of powder, which yields about 750-
800 mgs of elemental calcium (Nys, 2004) . The
composition of an eggshell is very similar to that of our bones
and teeth. It is recommended that people with osteoporosis
take 400-500 mg calcium per day to supplement dietary
sources. In laying hens in the late production phase, eggshell
powder has been found to increase egg production and
improve the quality of shells (Kingori, 2011) .
In wild before eggshell formation begins, the egg content has
to be almost completed. That makes sense! Female great tits
were found to deposit 60% of the calcium in the shell in less
than 8 hours, prior to laying. Whereby, the fat and protein
deposited in the egg is extended over a 4 day period. A
general feature of many wild birds is to lay down the calcium
needed to lay the night before laying (Bee, 2011) . Chemical
analyses showed that, eggshell is composed of about 97%
calcium carbonate, and most of the research on shell quality
concentrated on this fact (Hunton, 2005) .
However, eggshell is a valuable source material or additive for
numerous branches of the industry, such as, among others
fodder and fertilizer producers, paper manufacturers.
Numerous types of collagens, hyaluronic acid, or amino acids
of interest may be extracted from the egg shell membrane and
purified for numerous uses (e.g. dietary supplements,
cosmetics), which makes the separated eggshell membrane a
highly valuable material. This way the egg producers could
avoid the cost of waste disposal, moreover they can make
extra profit by selling their side product (Gaonkar and
Chakraborty, 2016) .
Materials and methods
Eggs of local and hybrid hen were bought from the market and
their shells were collected. Initially, nests of birds [Swift,
International Journal of Zoology Studies
Forest Pigeon, Lap wing] were traced and a constant
observation on these nests for a few days, and the birds were
identified. After hatching birds get rid of these shells by
dropping them out of the nest. These fallen eggshells were
collected manually. These collected samples were compared
and identified by using resources and based on the
morphology of the egg.
Determination of Caco3 in an egg shell
The Major component of eggshell is Calcium Carbonate
(CaCO3). This analysis will be done volumetrically by using a
characteristic reaction of carbonate compounds, namely their
reaction with acids. Calcium Carbonate (limestone) is very
insoluble in pure water but will readily dissolve in acid
according to the reaction.
2HCl (aq) + CaCO3(s) → Ca2+(aq) + CO2(g) + H2O +2Cl-(aq)
This reaction cannot be used directly to titrate the CaCO3
because it is very slow when the reaction is close to the
endpoint. Instead the determination was achieved by adding
on excess of acid to dissolve all of the CaCO3 and then
titrating the remaining H3O+ with NaOH solution to determine
the amount of acid which has not reacted with the calcium
carbonate. The difference between amount of the acid (HCl)
initially added and the amount left over after the reaction was
equal to the amount used by the CaCO3. The reaction used to
determine the leftover acid is
HCl (aq) + NaOH (aq) → H2O + Na+(aq) + Cl-(aq)
1. Clean the collected eggshells with water and dry them in
2. Use a mortar and pestle to grind the eggshells into a
3. Mass out 0.50 grams of the eggshell powder into a 100 ml
flask and record the mass of the powder.
4. Add several drops of ethanol to the flask (this helps to the
HCl to dissolve the eggshell but is not part of the reaction).
5. Pipette 10.0 ml of 1.0 M HCl into the flask. Then add 2-3
drops of Phenolphthalein.
6. Fill the burette to above the 0.0 ml mark with 0.1 M
NaOH. Open the value and allow the NaOH to drain into a
small beaker until the solution was at the 0.0 ml mark. The
small amount of NaOH in the beaker may be discarded.
7. Titrate the eggshell sample until the solution turns pink
and stays for 30 seconds. Read and record the final volume
on the burette.
8. Calculate the amount of CaCO3 present in eggshell using
Result and discussion
The eggshell is a highly specialized mineralized structure,
which provides protection against physical damage and
penetration by microorganisms. The egg shell consists of the
inner and outer shell membranes, the true shell and the cuticle.
The crystalline layer of the shell, which is responsible for its
mechanical strength, consists of more than 90% calcium in the
form of calcium carbonate. Calcium is absorbed from the feed
in the intestine. Provided that sufficient calcium (3.8–4.2%) is
present in the feed, the process of calcium uptake, deposition
and excretion is regulated by vitamin D3 and its metabolites.
According to our experimental analysis of eggshell samples,
the lap wing has the highest value of calcium egg weight
(0.4823 g), percentage of CaCO3 was 96.46. The swift has the
lowest value of calcium egg weight (0.3403g), percentage of
CaCO3 was 68.06 all on the average basis of seven eggs
involved in each case.
Present experimental results showed that the Lap wing which
has highest CaCO3 level (0.4823 gm, i.e. 96.46% ), followed
by the Hybrid hen (0.4764 gm, i.e. 95.28%), this is followed
by Forest Pigeon (0.4554 gm, i.e. 91%), then Domestic Pigeon
(0.4344 gm, i.e. 87%), then Rat snake (0.4034 gm, i.e., 81%),
then Local Hen (0.4 gm, i.e. 80%), and the swift eggshell
(0.3403 gm, i.e. 68.06%) sample which has the least level of
Lap wing > Hybrid Hen> forest Pigeon > Domestic Pigeon
> Rat Snake> Local hen> Swift
Table 1: Weight and percentage of CaCO3 present in different
CaCO3 in grams
The % of CaCO3
Fig 1: Weight and Percentage of CaCO3 present in eggshell samples.
Increased or decreased calcium level in birds might be
depending upon their habitat. In case of domestic birds, they
are fed with supplementary feed. This may be the reason for
the difference in the calcium content in birds’ egg shell. This
may increase the quality of egg shell.
Eggshells can be utilized for various purposes that minimize
their effect on environmental pollution. Eggshells present
healthy, balanced calcium due to its trace amounts of other
minerals and is probably the best natural source of calcium
(Adeyeye, 2009) . One whole medium sized eggshell makes
about one teaspoon of powder, which yields about 750-800
mgs of elemental calcium plus other micro elements. Eggshell
powder has been reported to increase bone mineral density in
people and animals with osteoporosis (Kingori, 2011) . In
laying hens in the late production phase, eggshell powder has
International Journal of Zoology Studies
been found to increase egg production and improve the quality
of shells. Discarded eggshells are often used as a plant
fertilizer and are effective liming sources. This is because
eggshells contain calcium that raises, or neutralizes, the pH
level of overly acidic soil.
Numerous factors affect the functional quality of the egg shell
mostly prior to the egg is laid. The thickness of the shell is
determined by the amount of time it spends in the shell gland
(uterus) and the rate of calcium deposition during shell
formation. If the egg spends a short period in the shell gland,
the thickness will be less. Also, the time of the day when the
egg is laid determines the thickness of the shell. Many studies
showed that saline drinking water, including tap water
containing sodium chloride supplied to mature laying hens at
concentrations similar to those found in underground bore
water, has an adverse effect on eggshell quality while having
little effect on feed intake, egg production or egg weight. In
contrast some reports indicate that there were no visible shell
defects and specific gravity was also not adversely affected.
One of the factors contributing to poorer eggshell quality in
hot weather is inadequate feed intake. Eggshell quality is
somewhat compromised during summer months. During
exposure to warm environmental temperature, the hen reacts
by increasing its rate of breathing (panting) in order to cool
itself. This causes the lowering of CO2 in the blood and
produces a condition termed "respiratory alkalosis". The pH of
the blood becomes alkaline and the availability of calcium for
the eggshell is reduced. This disturbance in acid-base balance
causes an increase in soft-shelled eggs during
summer. Temporary thinning of the egg shell may occur
during periods of high ambient temperature (above 25ºC)
since feed intake is reduced. The shells quickly regain normal
thickness when temperatures are reduced and feed intake
Calcium is vital to breeding birds and is needed in large
quantities for egg shell production and for the healthy growth
of the new born chicks. Without it young birds can be
unhealthy, eggshells can be defective causing clutch desertion
as the hatchlings never hatch, deformed or even die. In the
hen, calcium deficiency during the breeding period results in
poor egg shell formation and even to egg-binding. Giving
extra calcium to birds during the breeding and growth season
is therefore strongly recommended. Sufficient calcium ensures
good egg shell formation and the development of a healthy
skeleton. Calcium dietary supplement is administrated for
good egg shell formation, for good skeletal development in
young birds, during the breeding season to prevent egg-
binding and in cases of calcium deficiency or calcium tetany.
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