Like other chick quality parameters, hatchling length is an easy and repeatable
quality evaluation parameter for newly hatched chicks. This important trait has
a positive correlation with the size of the egg and the chick's weight. The
hatchling length is the best indicator of pre-incubation and incubation
conditions and for the rate of absorption of yolk after hatching in the body
cavity of the chick. Chicks with large lengths have heavier heart weights, liver
weights and bursa of Fabricius at hatch. The length at hatch can be measured
from the crown to toe and it can be improved by maintaining embryo temperature
until internal pipping, proper egg storage conditions, maximum turning of eggs,
maintaining the minimum egg weight losses at the 18th day of embryonic
development, maintaining ample O2 supply and removal of
CO2 through gas exchange programs, improved shell quality and better
health of the breeder flock.
The yolk does not play any role in the bird's future growth but it can create
many disease problems in the bird's life. A bigger, day-old chick has a large
residual yolk and a small yolk-free body mass. This characteristic does not play
any role in the development and growth during the incubation and post incubation
processes. In conclusion, hatchling length offers a fast, repeatable, and
non-destructive method to evaluate chick quality.