A 58-congener polychlorinated biphenyl (PCB) mixture based on contaminant analysis of spotted sandpiper eggs collected along the upper Hudson River, New York, USA, in 2004 was used to study in ovo PCB effects on cardiac development in the domestic chicken. Fertile eggs were injected prior to incubation with the following doses of the PCB mixture: untreated, sham, 0, 0.03, 0.08, 0.3, 0.5, 0.7, and 2.06 µg PCBs/g egg weight (toxic equivalent quotient [TEQ] range of 0.004-0.266 ng/g). In addition, there were untreated and sham-control groups. Embryonic development was monitored throughout incubation and chicks were necropsied at hatch. Hatchability followed a dose-dependent curve with significant (p < 0.05) mortality above the 0.5 µg PCBs/g egg weight treatment compared with controls. The median lethal dose (LD50) of this PCB mixture in hatchling chicks was estimated as 0.4 µg/g egg weight (0.052 ng TEQ/g egg wt) based on the lethality curve. Cardiac arrhythmia was observed at embryonic day 14 of development in embryos treated at concentrations of 0.5 µg/g egg weight and above. Histological analysis was utilized to characterize any cardiac abnormalities. Cardiomyopathies increased across treatments in a dose-dependent manner compared with control groups. Identified abnormalities included the absence of the trabeculated layer of the ventricular wall, ventricular dilation, thinning of the ventricular walls, malformation of the septal wall, and most commonly, absence of the compact layer of the ventricular wall. Chick heart width, depth, total area, compact layer depth, septal width, chamber area, and ventricular wall dimensions did not differ across treatments. The present study supports prior reports of adverse developmental effects of PCBs on cardiovascular systems in birds. Although the eggs hatched, measured cardiomyopathies suggest potential deleterious long-term impacts on individual health and fitness.

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The use of avian egg bioassays for the determination of embryonic mortality and development effects of toxicant exposure is widespread in ecotoxicology. While these studies have a number of experimental limitations to consider, they offer a rapid, cost effective alternative to maternal feeding studies. In preparing to conduct such studies a number of factors must be taken into consideration, including solubility of the toxicant, dissolution solvent, injection site, volume and incubation position. Species-specific requirements for humidity and position should be considered in order to optimize successful incubation with different species. Japanese quail eggs, were injected prior to incubation with 1ml or 5ml of corn oil, triolein or a fatty acid mix, using air cell or albumen injection. Eggs were incubated according to standard poultry practices or in a prone position to determine if there were any differences in hatching success. Hatching success was reduced in eggs that were injected with 5ml and those incubated in a prone position. The highest rate of hatching success was observed for eggs injected with 1ml of the fatty acid mixture through the air cell.

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