UBC Theses and Dissertations
An investigation of egg shell quality Lee, James Hin Foon
Egg shell quality was assessed in terms of breaking strength, elasticity, and energy absorbed by the shell up to failure. Two devices were used to determine these characteristics. Simple correlation and simple linear regression analyses showed that elasticity as determined by either device gave equally reliable estimates of breaking strength of the egg shell (r = -.68). A study of the three calcium levels supplemented to a basal ration on shell quality of eggs from two reciprocal crosses of birds showed that each measurement (breaking strength, elasticity, and energy to failure) used to assess shell quality produced different conclusions. In the early part of the experiment, elasticity was significantly lower for the 2% than for the 4% or 6% calcium diets in both crosses of birds. However, there was no significant difference in the effect of 4% and 6% calcium diets on elasticity. On the basis of the energy absorbed to failure, there was no significant effect of dietary calcium in Cross I birds. In Cross 2 birds, 6% calcium produced significantly superior results on energy absorbed as compared to the 2% and 4% calcium diets. For Cross I birds, breaking strength of eggs from the 6% and 4% dietary calcium treatments were significantly higher than those from the 7% calcium treatment. For Cross 2 birds, 4% dietary calcium produced stronger shells than 2%; shell strength from the 6% calcium treatment was inter, mediate to and net significantly different than that of the 2% or 4% calcium diets. No significant difference in the effect of the three calcium diets on shell quality as assessed by any one of the three measurements was observed in the latter part of the experiment. No consistent effect of the age of birds on egg shell strength was apparent. Significant variation in shell strength was found among groups of birds within the same cross on the same ration. Eggs stored under selected environmental conditions for different durations showed that moisture affected egg shell elasticity and the effect Increased In magnitude with time of storage when the egg was not only Immersed in water but also filled with water after removal of the albumen and yolk. Neither oiling nor storage temperature affected egg shell elasticity. There was no consistent effect of storage duration on egg shell elasticity except for the two treatments in which eggs with or without the contents removed were stored under water. It was found that the difference between the two duplicate elasticity readings measured at the equator of the same egg did not change significantly with either storage condition or storage duration.
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