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SUMMARY
Egg shell breakage is and remains a source of economic loss to the egg producer. In general, about 3% of the eggs laid by hens housed in battery cages or in free-run systems have cracked shells. This number increases about another 1% for hens kept in enriched cages or housed free-range and a further 1 to 2% for those in aviaries. The range of cracked shells reported was from 2 to 12%, but there were few published reports for most production systems. The occurrence of dirty-shelled eggs is about 2 to 3% higher than the incidence of eggs with cracked shells. Shell breakage is also influenced by manufacturer of enrich cage systems. The highest impact eggs receive as they move from the hen to the retail store is in the laying house; overall, eggs receive impacts that average about 13 G. The material used to make egg cartons (paper pulp or plastic foam), the cases in which the cartons are shipped (cardboard or wire), and the location of a carton within the shipping case (top, middle or bottom) affect the occurrence of shell breakage when eggs are transported. Even apparently weak impacts to egg shells may cause microcracks to develop and if the impacts are stronger visible cracks become apparent or they may rupture the mammillary membranes which will allow the egg’s content to escape.
Acknowledgements
No specific funding was received for this review. The authors thank Ms Keryn Eaton who prepared the figures in this review.
Disclosure statement
No potential conflict of interest was reported by the authors.
Notes
1. 1G = 9.81 N, which is equivalent to a 64 g egg being dropped 15.6 cm.
Additional information
Notes on contributors
R. M. G. Hamilton
Dr. Hamilton was a research scientist with Agriculture and Agri-Food Canada initially at their Animal Research Centre in Ottawa and later at the Atlantic Food and Horticulture Centre first in Kentville, Nova Scotia and then at the Nova Scotia Agriculture College at Truro. His areas of research were: egg shell strength and nutritional and physiological factors that influence egg shell strength; effects of trichothecene mycotoxins on the productive performance of poultry; evaluation of “novel” feedstuffs as ingredients for poultry, and effects of feed texture on poultry production. He has authored more than 150 articles of which 95 are papers published in national and international scientific journals. In 1970 he was recipient of the Honour Student Award from the American Oils Chemists’ Society and in 1981, the Young Scientist Award from the Poultry Science Association. By invitation, he was on the committees for graduate students, external examinator of thesis submitted to national and international universities by graduate students. Finally, he was the leader of the poultry nutrition program in Ottawa and Kentville for over 10 years. Dr. Hamilton was a member of the organising committee that planned the XXI World’s Poultry Congress that was held in 2000 in Montréal.
W. L. Bryden
Professor Bryden recently retired as Foundation Chair of Animal Science at the University of Queensland. Prior to that, he was Pro-Dean of the Faculty of Veterinary Science at the University of Sydney where he was also Director of the Poultry Research Foundation and is now an Honorary Governor of the Foundation. He has published over 600 papers of which 250 appear in international journals or as book chapters and he has supervised some 60 postgraduate research students. His research interests include various aspects of monogastric nutrition and production, especially of poultry. In 2009, Professor Bryden was the recipient of the Australian Poultry Award.