IN OVO CORTICOSTERONE ADMINISTRATION IN WATERFOWL: RESEARCH METHODOLOGY, AND ITS IMPACTS ON OFFSPRING DEVELOPMENT AND GLUCOCORTICOID AND MINERALOCORTICOID ABUNDANCE IN THE BRAIN
Date
2024-12-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Wetland species including Mallard Ducks (Anas platyrhynchos) can act as indicators of environmental health, where their health reflects environmental conditions. Disturbances, such as climate change, can act as stressors which may impact animal fitness. Stressors initiate a stress response, activating the hypothalamic-pituitary-axis (HPA) to release corticosterone (CORT) to enable the animal to respond to the stressor and restore homeostasis. If a hen experiences stress when laying, she may deposit higher CORT concentrations into the egg which can impact the developing embryo and post-hatch phenotype. Many studies utilize exogenous CORT injections to evaluate these effects. As most studies assume that CORT diffuses throughout the egg layers, the first objective was to quantify CORT concentrations in the yolk and albumen following in ovo exogenous CORT injections. Domestic Duck (Anas platyrhynchos domesticus) eggs were injected into either the air cell or albumen utilizing varying doses (15, 75 or 150 ng CORT/g of egg, n=8) or sesame oil (control). Dose did not affect viability; however, all injected eggs had increased CORT concentrations in yolk and albumen compared to control, demonstrating CORT diffusion across air cell membranes and albumen to the yolk. Albumen injected eggs had higher yolk CORT concentrations compared to air cell injected eggs. Given that CORT influences embryonic development, the second objective was to assess egg viability and phenotypic changes including hatch mass and glucocorticoid (GR) and mineralocorticoid (MR) receptor abundance in day-old duckling brains following in ovo exogenous CORT injection. Mallard Duck eggs randomly received varying doses (0, 15, 30, 75 ng CORT /g of egg). After hatch, ducklings were weighed and euthanized to collect brains which were later homogenized and analyzed for GR and MR receptor abundance via quantitative polymerase chain reaction (qPCR) and western blot. No relationship was observed between the hatch rate and CORT dose, but duckling mass was reduced at the highest dose (75 ng CORT/g of egg). Western blot but not qPCR identified a reduction in GR and MR receptor abundance in all treatment groups. This study demonstrated CORT diffusion in the egg and impacts of developmental stress on phenotype.
Description
Keywords
Avian, Egg, Corticosterone, Development
Citation
Degree
Master of Science (M.Sc.)
Department
Veterinary Biomedical Sciences
Program
Veterinary Biomedical Sciences