Methods and Factors That Affect the Measurement of Egg Shell Quality ,

Egg shell breakage accounts for a loss of 7 to 8% of the total eggs laid. Because shell breakage is related to egg shell strength, numerous methods have been developed to measure shell strength in relation to egg breakage. These methods can be divided into those that measure shell strength indirectly and those that measure directly. Egg specific gravity, nondestructive deformation, and beta backscatter are examples of indirect methods and quasi-static compression fracture, impact fracture, and puncture force are examples of direct measurements. A major advantage with indirect methods is that multiple measurements of shell strength may be taken on the same egg and the egg may be subsequently hatched, whereas with the direct methods the shell is fractured during the measurement. Factors known to influence the measurement of shell strength include the temperature of eggs, the length of time between oviposition and measurements, the sequence in which indirect measurements are taken, the compression rate and response time of recording equipment used to measure deformation, compression fracture and puncture force, the configuration and roughness of the surfaces of the measuring equipment that contact the egg shell, the deformation within the measuring equipment, and possibly the moisture content of the shell. Details of these factors should be reported with shell strength data. In general, there is a moderate relationship (r<.75) between data from indirect and direct shell strength measurements. There is a curvilinear relationship between shell strength and egg shell breakage. Further research is required to determine which of die indirect or direct methods best predict shell breakage under field conditions and to develop a model that will explain the strength of the hen's egg shell.