However,percentage YSW of chicks fr

However,
percentage YSW of chicks from breeders at 51 wk
of age have been reported to be smaller than those from
broiler breeders at 36 and 64 wk (Latour et al., 1998).
Current results indicated that percentage YSW of embryos
between 16 and 19 d of incubation was lower in
eggs from 26-wk-old breeders compared with those from
28-wk and 30-wk-old breeders. Likewise, Latour et al.
(1996) found that 18-d embryos from breeders at 26 wk
had a smaller percentage YSW when compared with
breeders at 36 and 48 wk. The yolk sac is the main nutrient
source for the developing embryo, as it absorbs yolk during
the final week of incubation. It would appear that
yolks of embryos from very young breeders (26 wk) may
be absorbed at a higher rate between 16 and 19 d than
those from hens that are slightly more mature (i.e., 28
and 30 wk). Subsequent declines in yolk absorption rate
after 19 d in the 26-wk-old group may, likewise, eliminate
or reverse comparative differences in residual percentage
YSW of posthatch chicks from very young and more mature
parents. Nevertheless, a relatively higher rate of yolk
uptake during the final week of incubation by embryos
from very young parents may stem from an effort to
compensate for possible deficiencies in yolk nutrient content
or inefficiencies in lipid transfer, nutrient utilization,
and metabolism. Differences in rate of yolk absorption