J. R. Hunt

Physical properties of egg shells

Synopsis A method of recording the stress distribution in egg shells about an applied force is described. Results indicate that the axes of stress can be predicted by a theoretical analysis, assuming the shell is spherical. The force required to fracture a shell was not predictable. From a theoretical approach, shell thickness, ultimate tensile strength and curvature were the important factors in shell strength. An external force produced tension at the inner shell surface and compression at the outer surface at the point of contact. The maximum tensile stress was at the point of application of force and diminished radially from this point. Because the shell material is brittle and therefore weaker in tension than in compression, the shell must fracture initially at the inner surface under the point of contact. It was concluded that shell behaviour in tension is a major factor contributing to shell strength.

Physical properties of egg shells: 3. An apparatus for estimating impact resistance of the shell

Synopsis A device is described for recording the maximum force imposed, by the impact of a falling steel rod, on egg shells. Maximum force occurred at the point of shell failure. Correlation between the maximum force during impact and shell thickness were highly significant but not considered adequate for predictive purposes. It was concluded that shell thickness accounted for only part of the variation in resistance of the shell to impact.

Effect of feeding system on protein metabolites in chick blood.

Synopsis Chicks, one week of age, were subjected to a cyclic feeding regimen where food was available for 8 h and withheld for 16 h while their controls had access to food 24 h/d. All birds were kept under continuous light. At the end of a 3‐week feeding period, blood uric acid and ammonia levels were determined with time of sampling related to the feeding regimen of the cyclic fed birds. It was found that access to food in the cyclic fed birds significantly elevated plasma uric acid levels as compared to the ad libitum fed birds. Blood ammonia, on the other hand, significantly decreased with feeding and increased after the withdrawal of food in the cyclic fed birds.