Several moderator variables were used to baseline information. Inclusion criteria
included moderator variables [study location, breed, treatment duration, age of
hens, number of hens used in the study, carotenoid (source, level, and form)
added to feed], as well as mean value, SD, and SE. The parameters observed were
egg quality [egg weight, shell thickness, egg yolk color, Haugh unit (HU), egg
yolk cholesterol (EYC), egg yolk carotenoids], performance (feed consumption,
FCR, final body weight, egg production), and immunity [immunoglobulin A (IgA)
and white blood cells (WBC)].