Yolkheight and yolkdiameterweremeasuredby the same
instrument and yolk index was calculated with the following
formula: yolk index = yolk height/[(long diameter of yolk +
short diameter of yolk)/2] × 100. Shape index was calculated
according to the following formula: shape index = (short
border/long border) × 100. Shell thickness wasmeasured by a
micrometer (Mitutoyo, 0.01 mm, Japan). Shell thickness was
a mean value of measurements at three locations on the eggs
(air cell, equator, and sharp end). Pigmentation of the egg yolk
was measured visually using the Roche color fan (RCF) scale
(Roche Ltd., Basel, Switzerland).