Differences in egg‐shell quality among the Sinai Bedouin fowl, the commercial white leghorn and their crossbreds

1. A comparison of egg‐shell characteristics was made among the Sinai breed (a desert inhabiting strain), the commercial White Leghorn and their reciprocal crossbreds. 2. The Sinai egg was smaller and its shell thicker and stronger than the Leghorn egg. All the differences were statistically significant. 3. Shell thickness and strength of Leghorn eggs were in accordance with values predicted on the basis of egg mass, while those of the Sinai and the two crosses were considerably higher than predicted. 4. The apparent differences in mean egg mass between Sinai and Leghorn breeds did not explain the differences in egg‐shell quality, neither did the shape index which was very similar among all breeds. 5. The findings suggest that the differences in egg‐shell properties are of a genetic origin. 6. The thick, strong and less permeable egg‐shell of the Sinai breed may reflect adaptations to its arid environmental origin and to incubation in the open. 7. These genetically‐determined egg‐shell characteristics mig...