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Relationship of Surrogate Vitellogenin with Selected Reproduction Parameters in Philippine Mallard (Anas platyrhynchos domesticus L.)

The vitellogenin (Vtg) profile is hypothesized as a nonlethal physiological index of reproductive state in Philippine mallard (Anas platyrhynchos domesticus Linn.). The circulating total serum zinc as surrogate Vtg at pre-lay period (17 to 22 week old) and sexual maturity (or age at first egg lay with mean±SD of 22.14±0.22 week old) were determined from blood sera of 340 ducks. The sera were assayed for Vtg zinc in duplicate using 96–well microplate and read the optical density at 415nm in a microplate reader (Model 680, S/N 123669). The total serum zinc concentration of the sample was calculated using the nonlinear regression formula ΔOD = a x [Zn2+] / b + [Zn2+] and used in evaluating relationships with body weight, liver weight and selected reproductive parameters, namely: ovary and oviduct weights (in wet basis), and gonadosomatic and oviductosomatic indices. Results show that the circulating Vtg follows nonlinearity indicating independence in Vtg production with respect to the age but the surge was prominent at onset of sexual maturity. This finding conforms to the demand for Vtg of developing ovarian follicles necessary for yolk development and maturation. This shows that the circulating Vtg follows a dynamic pattern common in all egg-laying (oviparous) species depending on biochemical, physiological, and metabolic requirements and utilization.