Aging in Laying Hens

Aging in Laying Hens

Aging in Laying Hens

The longer the period of egg laying period is (without a pause for molting), the poorer the shell quality. Twice as many eggs are cracked from hens over 40 weeks of age, compared to younger flocks, because of thinner and weaker shells. Molting restores a significant portion of previous cycle shell quality.  For instance, the average cracked eggs between 40-49 weeks old are 3.5% compared with 6.2% between 60-69 weeks old. The number of cracked eggs, hairline cracks(a very thin straight-line crack or line check), thin-shelled, porous, or soft eggs, and with rough surface increases.

The diet calcium retention or absorption is about 55% for young laying hens, and 40% for older layers. Some old birds may loss oviduct muscle tone and produce rough surface egg-shelled.

The egg contents related to the watery white (Haugh unit score should be 70; <50 is poor) diminishes with the age and the blood and/ or meat spots increases. Heights of 8 to 10 mm are considered as indicators of superior interior quality.

Feathering condition or feather cover of laying hens declines as the bird ages.

Observed Clinical Signs Happenings

Feather Abnormalities

  • A poor feathering condition or uneven feathers
  • Poor feather cover or feather loss

Shell defects

  • Rough-shelled Rough surface eggs
  • Thin-shelled and soft-shelled or porous eggs
  • Ungraded or second's eggs increased
  • Egg specific gravity score lower (should be above 1.080 (1.068 thin shells)

Internal Egg contents defects

  • Blood and or Meat spots
  • Watery White or White Haugh unit decreased score should be 70 poor 50

Aging in Laying Hens DOES NOT show, exhibit or manifest any of the following clinical signs happenings:

  • Egg drop
  • Mortality above the standard
  • Visibly sick birds
  • Flock behaviour activity change
  • Droppings abnormalities
  • Respiratory abnormalities
  • Neurological Nervous
  • Lameness or unusual movements, incoordination, ataxia
  • Eyes abnormalities
  • Head, Comb, Wattles, Face, Nostrils, Sinuses, Mount, Beak, Earlobes, abnormalities
  • Body Parts (Neck, wings, breast, abdomen, shanks, legs, hocks, feet, joints, vent, and skin) abnormalities
  • Feed Consumption Changes
  • Diet or Feed Changes
Causing Agents
Aging symptoms associated with age
Affected Systems/Organs
Deterioration of the reproductive system over time
Mainly Affects
Shell Quality. Interior Egg Quality
Good nutrition, good husbandry practices, the addition of anti-oxidants and certain feed additives seem to alleviate the effects of ageing. Culling (removing non-productive birds) should be a continuous process over the course of a flock's life. Culling should be intensified during the latter stages of laying cycle.
Suggested Actions
  • Can be dealt with in house
  • Technical assistance recommended
  • Can be managed with feed additives, off-the-shelf medications

Impact on Egg quality


Impact on Liveability


Impact on Production


Overall Economic Impact


Y.M. Saif. 2008. Disease of Poultry. 12th Edition.

David E. Swayne. 2013.  Diseases of Poultry 13th Edition.

Mark Pattison, Paul F. McMullin, Janet M. Bradbury. Dennis J. Alexander. 2008. Poultry Diseases. 6th Edition.

Paul McMullin. 2004. A pocket Guide to Poultry Health and Disease. First Edition. page 30

Steven Leeson, John D. Summers. 2008. Commercial Poultry Nutrition. Third Edition.

Donald D. Bell, Williams D. Weaver. 2009.  Commercial Chicken Meat and Egg Production. Fifth Edition. page 1101

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