However,the lack of any change in linoleic acid concentration
between 16 and 18 d and an elevation at 19 suggest that arachidonic acid was being absorbed at a slower rate
only. Because yolk sac membrane Δ-9 desaturase activity
converts stearic acid to oleic acid (Noble and Shand, 1985;
Noble and Cocchi, 1990), perhaps higher stearic and lower
oleic acid concentrations in the yolks of eggs from 26-
wk-old breeders compared with those at 30 wk may also
be due to decreased Δ-9 desaturase activity in the very
young hens relative to the slightly older birds. Nevertheless,
the significant effects of breeder age on yolk oleic
and arachidonic acid concentrations point to breeder age
effects on yolk sac membrane desaturase activity.