Comparison of breaking strength and shell thickness as evaluators of eggshell quality

Abstract

The shell quality of eggs produced by northern bobwhite (Colinus virginionus) dosed with sulfanilamide was evaluated by a compression breaking strength test and by the shell thickness measurements that are used in the US. Environmental Protection Agency avian reproduction test to determine the effect of a chemical substance on eggshells. The relative sensitivities of the two methods in detecting shell quality changes in sulfanilamide-treated quail were compared by relative response ratios, calculated as treatment period response divided by pretreatment values. The ratios demonstrated a clear shell weakening response and a less apparent shell thinning response. Significant differences in shell thickness of eggs from sulfanilamide-treated hens and those from control hens were not demonstrated ( a = 0.32 and 0.34), although highly significant differences in shell strength were demonstrated ( a < 0,0001). Scanning electron micrographs of weak shells of normal thickness revealed abnormal ultrastructure, usually poorly formed mammillae. Obtaining both shell thickness and shell strength information may provide better means to evaluate a chemical's effect on shell quality.

Effects of Methyl Parathion on Reproduction in the Japanese Quail

“…In the laboratory tests eggshell quality also may be influenced by disturbances of the housing conditions (unpublished data). Obtaining both shell thickness and shell strength information may provide better means to evaluate effects of chemicals on eggshell quality (Bennett et al 1988). …”

“…The mean value thickness for each egg was calculated from four thickness measurements. This was done after the eggs were cut around the equator with scissors, the contents except the membrane, removed and the shells dried for 2 days at room temperature according to Bennett et al (1988). Fertility rate and hatchability also were calculated.…”

Effects of Naturally Weathered Exxon Valdez Crude Oil on Mallard Reproduction

“…Eggs laid on the first day of weeks 1 , 3 , 5 , 7 , and 9 of the egg production period were used for shell thickness and strength measurements. Eggshell strength was measured following the method of Bennett et al [19] using an Instron testing machine (model 4202; Instron Testing Machines, Inc., Canton, MA). Eggshell thickness, including the shell membrane, of the same eggs used for eggshell strength was measured at four points around the circumference of the shell using a micrometer.…”

“…The poor quality of these eggs was attributed, in part, to markedly thinner eggshells of birds fed crude oil compared to those of study controls. Eggshell thinning has been correlated with decreased shell strength [19] and can result in eggs that are prone to breakage and are, thus, more susceptible to parental destruction. Reductions in eggshell thickness of approximately 33% have been observed in studies conducted with South Louisiana (3% in the diet) [5] and North Sea [6] crude oil (5% in the diet).…”

A Review and Analysis of Study Endpoints Relevant to the Assessment of “Long Term” Pesticide Toxicity in Avian and Mammalian Wildlife

“…As reviewed by recent workers (Carlisle et al, 1986;Bennett et al, 1988;Henny and Bennett, 1990), eggshell strength is a more sensitive measure of a change from the norm than eggshell thickness and can readily be tested with the proper equipment. Eggshell thickness does not address the underlying structural reason for a change and may correlate poorly with eggshell strength.…”