Vitellogenin (Vtg) is a large precursor molecule of the two major egg yolk phosphoproteins, namely; lipovitellin and phosvitin. All of the vitellogenic zinc is found in lipovitellin. Several reports had speculated into the probable relationships of Vtg with reproductive phenotype of Philippine Mallard duck (Anas platyrhynchos domesticus L.). Hence, it was hypothesized to use the Vtg profile as a nonlethal physiological index of reproductive performance in Philippine Mallard duck. Forty ducks, aged 16 weeks old, were randomly assigned into two treatment groups: 20 ducks fed with 30 ppm zinc-diet (zinc positive) and 20 ducks fed with no added zinc (zinc negative). All ducks were kept individually in cages. The circulating Vtg at sexual maturity (155.11±10.83 days old) was determined from the blood sera. The sera were assayed for Vtg in duplicate using 96-well microplate and the optical density was read at 415 nm. Results show that the circulating Vtg in the blood sera of ducks at sexual maturity was 0.69±0.07 μg Zn/dl. This circulating Vtg was identified to have negatively very weak to weak linear correlation with the majority of the laying traits (11 out of 17) in Philippine mallard duck.