This material will help to understand egg processing techniques.

1. Egg Shell

2. Egg Losses
 Poor egg shell quality is a huge
hidden cost to egg producers.
 More than 10% of eggs produced in
the hen house are uncollectible or
broken before intended use.

3. Cont. …
 The first 2-5%, they are lost simply due to form
which may be:
– Shell less
– Cracked or broken to the extent that they are not
suitable for collection.
 Another 3-8% is lost during:
– Collection
– Moving through the belts
– Cleaning
– Packing
– Transportation to the end user

4. Cont. …
 Egg producers estimate their egg
losses as the first 2-5% whom are
uncollectible eggs due to poor shell
quality.
 The economic losses for the breeders
will be even more due to reduced
hatchability and chick livability.
 Therefore, every effort must be
directed towards improving shell
quality and reducing egg breakage.

5. Egg Structure
The fertile egg is highly complexed
reproductive cell and is a tiny center
of life, where initial development of
embryo takes place.

6. Cont. …
Most of the commercial eggs are
infertile.

7. Cont. …

8. Cont. …
76%
12%
10%
2%
Egg Contents
Water Protein Lipids Minerals - Vitamins - CHO

9. Egg Shell Structure
Functions:
1. Protecting the contents of the egg from the microbial and physical
environment.
2. Controlling the exchange of water and gases.
Weight
5-6 gm
10% of total egg weight
Thickness:
300-350 micrometes.
Breaking strength
>30N

10. Eggshell Composition
1. Calcium carbonate:94-97%
– The calcium content of the eggshell is approximately 1.7-2.5g.
2. Phosphorus:0.3%
3. Magnesium:0.2%
4. Sodium, Potassium, Manganese, Iron and Copper: traces
5. Organic matter:< 2%, it is consisted of:
1. Matrix proteins
• They are mixture of proteins and polysaccharides rich in
sulphated molecules.
• They are critically important in determining the egg shell
structure and serves as foundation for the deposition of calcium
carbonate.
2. Shell pigment.

11. Cont. …
 There are about 8000 microscopic
pores on the shell.
 The outer surface of the shell itself
consists of a mucous coating
(cuticle) which is deposited on the
egg just prior to the lay.
 This proteinous covering helps to
protect the interior content of the
egg from bacterial penetration
through the shell.

12. Cont. …

13. Shell Quality
The aesthetic quality of the egg shell relates to the quality
factors which one can observe; such as:
1. Soundness of the shell.
2. Shape of the shell.
3. Colour of the shell.

14. Cont. …
However, for commercial layer and breeder operations, shell
quality means:
1. Increased shell thickness
2. Increased shell breaking strength
To:
1. Reduce number of cracked eggs
2. Increase number of saleable/ hatching eggs
3. Higher number of viable day old chicks.

15. Egg Shell Quality Defects

16. Shell Quality Defects
 Eggshell quality defects are obvious by direct external
observation or by candling.
 They are important for evaluation for the producer and
consumer.
 It is also the main criteria for selecting hatching eggs.

17. Shell Quality Defects
1. Misshaped Eggs
2. Sandpaper or Rough Shelled Eggs
3. Soft, Weak or Shell less Eggs
4. Dirty and Glazed Shells or Stained Eggs
5. Body Checks
6. Cracked Eggs
1. Gross Cracks
2. Hairline Cracks
3. Star Cracks
7. Flat-sided Eggs
8. Pimples
9. Pinholes
10. Mottled or Glassy Shells
11. Fungus or Mildew on Shells
12. Cage Marks Shells
13. Fly Marks Shells

18. 1- Misshaped Eggs
Description
 Misshapen eggs are those whose shells differ
obviously from the smooth, ‘normal’ shape.
 They include eggs with shells marred by flat
sides or body checks (ribs or grooves), and
eggs that are too large or too round.

19. Cont. …
Incidence
 Normally, up to 2% of production is downgraded due to these
faults.
 They are often produced by pullets coming into lay, or hens
late in lay.

20. Cont. …
Cause Control
Immature shell gland
• Delay onset of sexual maturity 1 to 2 weeks by controlled
feeding during rearing.
Defective shell gland • Cull birds which persistently produce such eggs.
Diseases, e.g. infections
bronchitis
• Follow an effective vaccination program
Stress, e.g. frights and
disturbances
To avoid frightening birds;
• Minimize human activity in and around the shed.
• Increase shed security to stop other birds and animals
entering the shed.
Crowding • Avoid overstocking.

21. 2- Sandpaper or Rough Shelled Eggs
Description
 The terms ‘sandpaper shells’ and ‘rough
shells’ refer to eggs with rough-textured
areas, often unevenly distributed over
the shell.

22. Cont. …
Incidence
 The incidence is normally less than 1% of total production.
 It may be higher in:
1. Some strains of bird.
2. Birds in early lay.

23. Cont. …
Cause Control
Diseases, e.g. infectious bronchitis,
infectious laryngotracheitis or avian
encephalomyelitis
• Follow effective vaccination program.
Defective shell gland • Cull such birds.
Disturbances at the time a hen is due to lay
can cause the egg to be held over for
another day
• Minimize activities which create
disturbances in and around the shed.
• Increase shed security to stop other
birds and animals entering the shed.
Incorrect or changes in lighting programme
• There should not be sudden increases in
day length as pullets come into lay, or
lighting changes during lay.
Water shortages
• Make sure that the water supply is
adequate, that there are no blockages in
water lines and that drinkers are
functioning property.

24. Cont. …
Another cause:
 In some cases, two eggs may be in the shell gland at the same
time which can cause a form of rough shelled egg often
referred to as a ‘target’ or ‘thumb-print’ type.

25. 3- Soft, Weak or Shell less Eggs
Description
 Eggs with very thin shells, or no shell at
all around the shell membrane.
 They look unattractive and are highly
susceptible to damage.

26. Cont. …
Incidence
 The incidence of these eggs varies from about 0.5 to 6%.
 They are commonly produced by:
1. Pullets coming into lay, particularly by birds that have matured early.
2. Older birds, especially those which are nearing the end of the laying
period, having produced a high output of eggs.

27. Cont. …
Cause Control
Immature shell gland
• Delay onset of sexual maturity 1 to 2 weeks by
controlled feeding during rearing.
Defective shell gland • Cull birds which persistently produce such eggs.
Disturbances causing eggs to be
laid before calcification of the
shell is complete
• Minimize activities which create disturbances in
and around the layer shed.
• Increase shed security to stop other birds and
animals entering the shed.
Poor nutrition
• Make sure that birds’ nutrient intake is correct
(particularly regarding calcium and vitamin D3).
• Mixed feed should be handled carefully so that
the different components do not separate out.
• This particularly needs to be checked when augers
and automatic feeding systems are used.

28. Cont. …
Cause Control
Saline water
• Desalinate, dilute or do not use drinking water
containing problem levels of salts.
Diseases, e.g. infectious
bronchitis and eggdrop
syndrome
• Follow effective vaccination programs where
available.

29. Cont. …
Another causes:
 If an egg is retained in the shell gland for too long;
– The next ovulation takes place at the usual time but before the
previous egg is laid.
– The second egg may spend less time than normal in the shell gland
and the result is a soft or shell-less egg.
– In such cases, a hen may not lay an egg on one day, but may lay both a
coated and a soft-shelled egg on the next.

30. 4- Dirty and Glazed Shells (Stained Eggs)
Description
 All or part of the egg shell may become
stained by various substances, e.g.
blood, faeces.

31. Cont. …
Incidence
 The incidence of stained eggs varies, partly because stains
may be caused by a variety of substances.
 Smears of blood are more common on eggs from pullets in
early lay.

32. Cont. …
Cause Control
Water stains
• Minimize roof condensation, which can drip onto eggs, by
providing adequate shed ventilation.
• Eliminate drips from faulty misting nipples and drinker
lines.
Blood from a prolapsed
cloaca, cannibalism or
vent picking
• Do not allow pullets to become over-fat, as the incidence
of prolapse is greater in fat birds.
• There should not be sudden large increases in day length
as pullets come into lay.
• Regularly clean cage bottoms and roll-out trays.
• Clean belt pick-up systems.

33. Cont. …
Cause Control
Sanitizers used in egg washing
• Make sure that sanitizers in washing solutions are
properly dissolved and used at the correct
concentrations.
Grease and oil stains
• Do not allow eggs to become contaminated by
lubricants on rollers in packing systems.
Certain drugs produce mottled
shells or white shells in breeds
that normally lay brown eggs.
The drug chlortetracycline
produces yellow shells.
• Do not feed to layers or pullets just before lay.
• Follow correct procedures for medication, including
not feeding the medication for the required
withholding time before eggs are collected, to
prevent residues.

34. Cont. …
Cause Control
Faecal contamination
• Keep nest boxes supplied with clean nesting material.
• Maintain proper hygiene, follow effective vaccination
programmes and, when necessary, use appropriate
medication to keep birds free of diseases which cause
enteritis.
• Feed should not contain high levels of ingredients causing
loose or sticky droppings, such as molasses and high-
tannin sorghums.

35. Body Checks
Description
 The shells are marked by grooves and
ridges “checks”.
 They are usually at the ends of the egg,
especially the pointed end.
 Checks at the middle, or ‘waist’, often
completely encircle the egg.

36. Cont. …
Cause
 Checks are the result of repairs to damage caused by stress or
pressure when the egg is in the shell gland.
 This stage of development usually occurs in the last hours of
the light period or the first half of the dark period.

37. Cont. …
Incidence
 The percentage of body-checked eggs increases with flock
age: at 35 weeks it can be up to 1%; at 60 weeks it can be 9%.
Complications
 With table eggs, it creates an increased risk of breakage en
route to the consumer and lowers the utility value of the egg.
 With hatching egg, it is major factor contributing to cracks
during storage and results in lower hatchability.

38. Cont. …
Cause Control
Ageing of bird • Keep flock age as low as economically possible.
Keep flock age as
low as economically
possible.
• Minimize human activity in and around the layer shed, particularly
during the critical period of the last few hours of the light period
and the first half of the dark period.
• Increase shed security to stop other birds and animals entering the
shed.
Incorrect lighting
programme
Avoid using lighting program that keep birds active during the
critical period.
Where possible, light periods should not be longer than 15 hours.
Do not use lighting program which allow for a ‘midnight snack’.
Crowding • Avoid overstocking, particularly as birds become older.
Disease
• Make sure that layer stock come from parent stock vaccinated
against infectious bursal disease.

39. Cracked Eggs
 Egg shells can easily be damaged after the egg is laid.
 Cracking is one of the most common reasons for
downgrading.
 It may be due either to an inadequate egg shell being laid or
to poor handling which may occur during collection, grading
or transportation.

40. Gross Cracks
Description
 The term ‘gross cracks’ refers to large
cracks and holes, which usually result in
a broken shell membrane.

41. Cont. …
Incidence
 The incidence of gross cracks increases with the age of the
hen.
 It ranges from 1 to 5% of total production.

42. Cont. …
Cause Control
Reduced shell strength due to:
Ageing • Keep flock age as low as economically possible.
Poor nutrition
• Make sure that the birds’ nutrient intake is correct
(particularly regarding calcium and vitamin D3).
• Mixed feed should be handled carefully so that the
different components do not separate out.
• This particularly needs to be checked when augers
and automatic feeding systems are used.
Saline water
• Desalinate, dilute or do not use drinking water
containing problem levels of salts.
Diseases such as infectious
bronchitis
• Follow an effective vaccination programm.

43. Cont. …
Cause Control
High shed temperatures
• Control temperatures by using foggers, fans, roof
sprinklers, white roofs, insulation and good
ventilation.
Mechanical damage caused
by birds’ beaks and toenails
• Control egg eating by the birds.
• Make sure that birds do not have access to eggs in
roll-out trays. Use cages designed to prevent access.
• Reduce damage caused by the birds’ toenails.
• The slope and construction of the cage floor should
allow the eggs to move freely to the roll-out tray.
Infrequent egg collection • Collect eggs at least twice a day.

44. Cont. …
Cause Control
Rough handling
• Do not collect eggs in wire baskets.
• When stacking fillers of eggs, place one empty filler at the
bottom of the stack, and a full one directly on top of it. This
double bottom layer supports the weight of the stack better.
• Avoid stacking fillers of eggs more than six high.
• Pick up and carry stacks with care.
• Place large eggs on top fillers in a stack.
• Reduce the severity of impacts during mechanical handling by:
• Cushioning metal egg guides;
• Keeping egg roll-out angles between 7 and 8°;
• Minimizing the number of rows of eggs being fed onto cross-
conveyor belts at any one time.
• Educate staff to handle eggs with care during collection and
packing.

45. Hairline Cracks
Description
 They very fine cracks, usually run
lengthwise along the shell.
 They are difficult to detect, candling
efficiency needs to be maximized.
 Their presence in fresh eggs can be
revealed by careful squeezing or tapping.
 They are the most difficult to identify,
particularly in very fresh eggs.
 Hairline cracks are often caused by an egg
colliding with an inflexible surface.

46. Cont. …
Incidence
 The incidence of this problem varies with flock age, but is
usually 1 to 3% of total production.

47. Cont. …
Cause Control
Reduced shell strength due to:
Ageing • Keep flock age as low as economically possible.
Poor nutrition
• Make sure that the birds’ nutrient intake is correct
(particularly regarding calcium and vitamin D3)
• Mixed feed should be handled carefully so that the
different components do not separate out.
• This particularly needs to be checked when augers
and automatic feeding systems are used.
Saline water
• Desalinate, dilute or do not use drinking water
containing problem levels of salts.
Diseases such as infectious
bronchitis
• Follow an effective vaccination program.

48. Cont. …
Cause Control
High shed temperatures
• Control temperatures by using foggers, fans, roof
sprinklers, white roofs, insulation and good
ventilation.
Mechanical damage caused by
birds’ beaks and toenails
Make sure that:
• the cage floor is not too rigid.
• the slope of the floor is just enough to allow eggs to
roll out.
• roll-out trays cushion the eggs as they come to rest
against the edge of the tray.
Infrequent egg collection • Collect eggs at least twice a day.

49. Cont. …
Cause Control
Rough handling
• Do not collect eggs in wire baskets.
• When stacking fillers of eggs, place one empty filler at the
bottom of the stack, and a full one directly on top of it.
• This double bottom layer supports the weight of the stack
better.
• Avoid stacking fillers of eggs more than six high.
• Pick up and carry stacks with care.
• Place large eggs on top fillers in a stack.
• Reduce the severity of impacts during mechanical handling
by: • cushioning metal egg guides. • keeping egg roll-out
angles between 7 and 8°. • minimizing the number of rows
of eggs being fed onto cross-conveyor belts at any one time.
• Educate staff to handle eggs with care during collection and
packing.

50. Star Cracks
Description
 Star cracks are fine cracks radiating
outwards from a central point of
impact, which is often slightly indented.

51. Cont. …
Incidence
 The incidence varies with flock age but is usually 1 to 2% of
total production.

52. Cont. …
Cause Control
Reduced shell strength due to:
Ageing • Keep flock age as low as economically possible.
Poor nutrition
• Make sure that the birds’ nutrient intake is correct
(particularly regarding calcium and vitamin D3) Mixed
feed should be handled carefully so that the different
components do not separate out.
• This particularly needs to be checked when augers and
automatic feeding systems are used.
Saline water
• Desalinate, dilute or do not use drinking water
containing problem levels of salts.
Diseases such as infectious
bronchitis
• Follow an effective vaccination program.
High shed temperatures
Control temperatures by using foggers, fans, roof
sprinklers, white roofs, insulation and good ventilation.

53. Cont. …
Cause Control
Mechanical
damage caused
by birds’ beaks
and toenails
Make sure that:
• The cage floor is not too rigid.
• The slope of the floor is just enough to allow eggs to roll out.
• Roll-out trays cushion the eggs as they come to rest
against the edge of the tray.
Infrequent egg
collection
• Collect eggs at least twice a day.
Rough handling
• Do not collect eggs in wire baskets.
• Reduce the severity of impacts during mechanical handling by:
• cushioning metal egg guides.
• keeping egg roll-out angles between 7 and 8°.
• minimising the number of rows of eggs being fed
onto cross-conveyor belts at any one time.
• Educate staff to handle eggs with care during collection and
packing.

54. Flat-sided Eggs
Description
 Eggs are said to be flat-sided when part
of the shell is flattened or indented.

55. Cont. …
Incidence
 Flat-sided eggs normally make up less than 1% of total
production.
 They are most commonly produced by pullets in early lay and
may be the result of double ovulation or being held over an
extra day in the shell gland.
 Incidence can vary with the strain of bird.

56. Cont. …
Cause Control
Disease; traditionally linked with infectious
bronchitis
• Follow an effective vaccination program.
Stress, e.g. frights and disturbances
• To avoid frightening birds, minimize
human activity in and around the shed.
• Increase shed security to stop other
birds and animals entering the shed.
Crowding • Avoid overstocking.
Incorrect or changes in the lighting
programme
• There should not be sudden, large
increases in day length as pullets come
into lay.

57. Pimples
Description
 Pimples are small lumps of calcified
material on the egg shell.
 Some can be broken off easily without
damage to the shell while others may
leave a small hole in the shell.

58. Cont. …
Incidence
 An incidence of about 1% of total production is common.

59. Cont. …
Cause Control
Thought to be caused by foreign material in the oviduct, which may be associated with:
Ageing of bird
• Keep flock age as low as economically
possible.
Poor nutrition • Prevent excess calcium intake in winter.
Strain of bird
• Be aware that some strains may produce
eggs with a higher incidence of this
fault.

60. Pinholes
Description and
 Pinholes, or very small holes in the egg
shell.

61. Cont. …
Incidence
 usually affect less than 0.5% of total production.

62. Cont. …
Cause Control
May result from faulty laying down of the egg shell or from pimples being knocked off
the shell. Both problems are thought to be associated with:
Ageing of bird
• Keep flock age as low as economically
possible.
Poor nutrition • Prevent excess calcium intake in winter.
Strain of bird
• Choose a strain which produces eggs
with a lower incidence of this fault.
Damage from toenail points or other small
sharp projections
• Make sure that cage floor slope is
enough to allow eggs to roll away easily
from the birds.
• Remove sharp projections on cages and
roll-out trays.

63. Mottled or Glassy Shells
Description
 When parts of the egg shell are
translucent, it appears mottled or
glassy. Such shells can also be thin and
fragile.

64. Cont. …
Description
 When parts of the egg shell are translucent, it appears
mottled or glassy. Such shells can also be thin and fragile.

65. Cont. …
Cause Control
Failure of the egg shell to dry out quickly after laying, which is made worse by:
High humidity in the layer shed • The shed must be well ventilated.
Crowding • Avoid overstocking.
Disease
• Make sure that layer stock come from
parent stock vaccinated against
infectious bursal disease.

66. Fungus or Mildew on Shells
Description
 Eggs affected by a fungus may have a
green coating of powdery material or a
black, beard-like growth on the shell.

67. Cont. …
Incidence
 This defect should not occur under good management.
 Any incidence is unacceptable.

68. Cont. …
Cause Control
Poor hygiene during handling,
storage and transport
• Do not use soiled egg-handling equipment.
• Regularly clean roll-out trays, collection belts and
egg fillers.
• Use correct egg-washing sanitisers and
procedures.
• Clean and disinfect coolrooms regularly.
Warm storage conditions or
excess coolroom storage of eggs
with other produce
• The storage temperature must be under 15 °C,
and the humidity in the storage room under 80%.
• Store only eggs in the cool room.
Old eggs
• Do not keep old eggs in handling and storage
areas because they are more prone to fungal
attack.

69. Cage Marks Shells
Description
 'Cage marks' is the term used to refer to
dirty marks, dirty lines or translucent
lines on the shell when eggs are
collected.

70. Cont. …
Incidence
 In well-managed flocks, the incidence of this problem should
be under 5%.

71. Cont. …
Cause Control
Dirty marks or lines are due to:
Rusty or dirty wires in the
cage fl oor or roll-out trays
• Check wire floors, if they are rusty, either:
• replace the floors.
• regalvanise if possible, or
• paint with a light-coloured paint.
• Brush roll-out trays regularly to keep them clean.
• Do not allow excessive build-up of manure under
cages.
• Remove manure caught in cage floors.
• Do not allow ammonia to build up in sheds, as it causes
corrosion of metal cages.
• Make sure ventilation is adequate and that manure is
kept dry.

72. Cont. …
Cause Control
Translucent lines result when the shell fails to dry out quickly after laying, which is
made worse by:
High humidity in the layer
shed
• The shed must be well ventilated.
Crowding • Avoid overstocking.

73. Fly Marks Shells
Description
 Fly marks are caused by flies leaving
droppings on the egg shell.

74. Cont. …
Incidence
 This defect should not occur under good management.
 Any incidence is unacceptable.

75. Cont. …
Cause Control
Eggs exposed to large numbers
of flies
• Control flies on the farm by maintaining a high
level of hygiene, by keeping manure dry and not
allowing it to build up excessively and, when
necessary, by using approved insecticides.
• Use UV fly traps in egg-handling rooms.
• Put fly screens on doors and windows in handling,
packing and storage rooms.
• Collect eggs frequently.
• Store eggs in a cool room.