A series of egg injection studies were conducted to assess the potency of two furan congeners relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in three Galliform species; as well as, confirm the order of sensitivity for these species as has been previously predicted based on in vitro EROD assays in primary hepatocyte cultures and key amino acids of the ligand-binding domain of the aryl hydrocarbon receptor. This avian species sensitivity classification model states; those species with amino acid sequences similar to that of the White Leghorn chicken (Gallus gallus domesticus) will be most sensitive, those similar to the Common pheasant (Phasianus colchicus) will be moderately sensitive, and those with amino acid sequences similar to the Japanese quail (Corturnix japonica) will be least sensitive to TCDD-like toxicity. Doses ranging from 0.044 to 37 pmol/g egg were injected into the air cell of eggs prior to incubation. LD50 (95% confidence intervals) values, based on hatchability, for TCDD, PeCDF and TCDF were 30 (25 - 3`6), 4.9 (2.3 - 9.2) and 15 (11 - 24) pmol/g egg for the quail, 3.5 (2.3 - 6.3), 0.61 (0.28 - 1.2) and 1.2 (0.62 - 2.2) pmol/g egg for the pheasant and 0.66 (0.47 - 0.90), 0.75 (0.64 - 0.87) and 0.33 (0.23 - 0.45) pmol/g egg for the chicken, respectively. Relative potencies of PeCDF and TCDF were 6.1 and 2.0 for the quail, 5.7 and 2.9 for the pheasant and 0.88 and 2.0 for the chicken. Developmental stages of embryo mortality, incidences of deformities, body mass, relative organ mass and histopathology of liver, heart, brain, bursa and spleen tissues were also evaluated. TCDD was not the most potent embryo toxic compound among the species tested. PeCDF and TCDF were more potent than TCDD in the quail and pheasant, while only TCDF was more potent in the chicken. Species sensitivity was as expected for TCDD and TCDF; while for PeCDF, the chicken and pheasant were similar in sensitivity and both were more sensitive than the quail.
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