Avian Species Comparison Study—a Protocol Development Study for the Avian 2-generation Tier Ii Assay

Executive Summary: A two-generation dietary test provides a method for determining multigenerational effects of endocrine disrupting chemicals (EDCs), with varied exposures over the stages in the life cycle. The Japanese quail has been developed as a model for precocial avian species; however, northern bobwhite quail have been the standard for toxicological testing. Our purpose was to compare relevant end points in these species, in a two-generation dietary study. In addition the to species comparison, a range of potential measurement end points were examined, including appraisal of potential sensitivity, constraints, and reliability for regulatory application. A modification of the OECD one generation protocol was followed with each generation for definition of the adult experimental phase of the study. The first generation (parental generation) was synchronized by raising both species under short photoperiod until mature. Specifically, Japanese and northern bobwhite quail (parents; P) were raised under short photoperiod, then placed on diet containing low concentrations of methoxychlor (MXC; 0, 5ppm, and 10ppm) and simultaneously photostimulated. A range of measures were monitored including feed intake, egg production, egg quality, fertility, offspring viability. In addition, other measures were selected for their potential to detect endocrine disruption. Chicks (F1) were raised on the same diet as their parents, paired as adults, and sexual maturation, reproductive behavior and endocrine measures were examined, similar to the parent generation. F2 chicks were raised on control feed and assessed for the same end points as the F1 birds. There were some inherent species differences, including slower maturation and lower productivity in bobwhite quail. These differences were observed consistently over all generations in both species. No treatment effects were observed in either species for body weight, feed intake, egg quality, or viability. Effects of 5ppm MXC were similar in both species, and no treatment effects were observed for egg production, shell quality, fertility, and chick growth. However, both species showed delayed sexual maturation with treatment. This was more pronounced in the 10ppm MXC treatment, with significant (p<0.05) reduction in the number of birds achieving optimal reproductive performance. Sexual behavior was significantly (p<0.05) impaired by MXC exposure in both F1 and F2 Japanese quail males; behavioral assessment was not conducted in bobwhite males due to species differences in courtship and mating behavior. A modified open field test was developed and pilot data was collected to assess potential impairment of motor and behavioral responses in young chicks. This testing method has potential …