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Plasma Yolk Precursor Dynamics during Egg Production by Female Greater Scaup (Aythya marila): Characterization and Indices of Reproductive State

1Centre for Wildlife Ecology, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada; 2Centre for Wildlife Ecology, Simon Fraser University, 5421 Robertson Road, Delta, British Columbia V5K 3N2, Canada; 3Poultry Science Department, Texas A&M University, College Station, Texas 77843

We characterized dynamics of the plasma yolk precursors vitellogenin (VTG), very‐low‐density lipoprotein (total VLDL‐TG), and VLDL particle size distribution during egg production by female greater scaup (order: Anseriformes, Aythya marila). We also evaluated VTG and total VLDL‐TG as physiological indices of reproductive state. Mean (±1 SE) plasma concentrations of VTG and total VLDL‐TG for females with nondeveloped ovaries were 0.58 ± 0.05 μg Zn mL−1 and 3.75 ± 0.29 mmol TG L−1, respectively. Yolk precursor concentrations increased rapidly to maximum levels in association with small increases in ovary mass during rapid follicle growth. Mean concentrations of VTG and total VLDL‐TG for females with a full ovarian follicle hierarchy were 3.38 ± 0.40 μg Zn mL−1 and 7.31 ± 2.56 mmol TG L−1, respectively. Concentrations of VTG and total VLDL remained elevated throughout the laying cycle and decreased markedly by 3 d into incubation. Individual reproductive state (non‐egg producing vs. egg producing) was more accurately identified by plasma profiles of VTG (90%) than by those of total VLDL‐TG (74%). Greater scaup VLDL particle sizes during egg production were within the range for predicted yolk‐targeted VLDL size (25–44 nm). We conclude that plasma profiles of VTG and total VLDL‐TG can be used as nonlethal, physiological indices of reproductive state in greater scaup and should be of great utility to a variety of evolutionary, ecological, and applied conservation studies of reproduction in waterfowl.