Introduction
The aim of every commercial layer hatchery is a maximum hatchability of rst quality chicks. Only healthy and vital chicks are able
to have a good start in the rearing period after being handled and
transported. Good chick quality is clear to see with a low rst week
mortality rate and a uniform development of the whole ock. It is
therefore the key to success not only for the hatchery but also the
rearing farm.
A rst indicator for chick quality is the percentage of second grade chicks. This percentage is naturally inuenced by
the age of the breeder ock. Young breeder ocks, e.g. at
< 30 weeks, usually give poorer results. If the chick quality does not improve with the age of the breeder ock,
examinations need to be performed in order to nd
out the causes. These causes can either be the age
of the hatching egg and the general quality of the
same, transport and storage conditions as well as the
disinfection of the hatching eggs. Hatchery-related
conditions might also have an impact on the
quality of day old chicks. These include temperature, humidity levels, ventilation, frequency and the angle of turning during
incubation.
The evaluation of chick quality in
the hatchery provides important information on the whole production
process. If properly applied, it can be
used to detect possible weaknesses of
the hatchery and the working routines in
the same. Either quantitative or qualitative
traits can be used for the measurement of
chick quality. The qualitative traits are namely Chick weight, Chick Yield, Chick Length and
Feather Length. Qualitative traits include the Vitality of the Chicks, the Quality of their Navel, their
Beaks and Joints. Many hatcheries still hesitate to
apply the examination of the qualitative traits in
their quality monitoring program as these traits are
highly subjective and hardly reliable.
There are, however, methods that can help to measure the qualitative traits as objectively as possible, i.e. by reducing the individual subjectivity to a minimum. These so-called “scoring” systems
enable recordings of the rst visual quality traits of a chick to be
transformed into a quantifying assessment with a maximum score
of 10 points. For every negative factor, one point will be deducted
from the total of 10 points.
Parameters that can be included in the scoring system are all of the above-mentioned qualitative traits as well as additional factors, e.g. the e ciency
of vaccination and injuries. This
can help to monitor and improve the chick processing quality.
At which point of the production process should
chick quality be investigated?
The point of investigation should be determined by the aim of the
quality control. If these
investigations serve
the primary purpose of
improving internal production processes, then
chick quality should be
investigated at takeo . The
advantage of this is that at this
point of the production chain,
an overview of the quality of all hatched chicks can be attained. This helps to
make conclusions about the incubation process and can give important hints
on what needs to be improved. If it is desired to get an
overview about the quality
Review of di erent day-old
chick quality parameters in
layer type breeds
of the chicks that will be handed over to the customers, and if
information about the sorting and handling of the chicks are just
as required, then it can be more appropriate to conduct the examinations before transporting the chicks. At this point, the quality
of the vaccination and chick handling can be evaluated as well.
Quantitative Traits
Chick Weight
Chick weight is highly correlated with egg weight and therefore
relatively predictable. If the incubation process is done properly,
the chick weight will be 2/3 of the egg weight. An extended or
reduced incubation time as well as too high or too low temperatures and humidity levels during incubation can also have an im
pact on chick weight. The longer the chicks stay in the hatcher, the
more weight they will lose due to dehydration. On the other hand,
if the chicks are pulled early, the chick weight can be higher than
expected. Two methods can be used for measuring chick weight:
1. Take single chick weights of a certain number of chicks. This
allows to calculate the variation of chick weights within the group
investigated in addition to the average. A good or bad uniformity
of chick weight can be used as an indication of the quality of hatching egg grading.
2. The other possibility is to weigh a certain number of chicks
at one time and calculate the average. This is a good and simple
method, i.e. if only the average chick weight is of interest.
Recording single chick weight at the hatchery
Weighing a certain number of chicks. Please don’t forget to subtract the
weight of the hatcher basket before calculating the average chick weight!
Chick Yield
In relation with the chick weight, the quantitative trait “Chick Yield”
(Chick weight at hatch in % of the egg weight at point of set)
must be mentioned. This is a simple method of checking whether
the hatch time and incubation parameters are correct. To accurately measure chick yield, it is important to measure the weight of
completely lled setter trays at the point of setting and to calculate the average egg weight. (Please do not forget to subtract the
weight of the empty setter tray before calculating the average
egg weight). The weighed setter trays must be labelled in order
to identify them on the day of transfer. On the day of hatch, the
chicks which originate from these labelled setter trays must be
weighed in order to calculate the average chick weight. The ideal
chick weight should be between 66–67 % of the egg weight. If
the chick weight is below target, this can be an indicator that the
chicks were pulled too late and are therefore at the risk of dehydration. It can also be a sign that the humidity level chosen during
incubation was too low. If chicks are required to travel long distances, it can be appropriate to aim for a chick yield which is about
1 % higher than the ideal of 66–67 %. This can help to guarantee
that the chicks arrive as fresh as possible at the rearing farm. In
order to achieve reliable results in terms of chick yield, at least 70
eggs and 70 chicks per breeder ock must be weighed. It will surely be more accurate if from every ock, 3 setter trays in di erent
positions in the setter are investigated.
Chick Length
In addition to chick weight and chick yield, the length of the
chicks is another quantitative trait which can be recorded in the
hatchery. In order to measure a chick, it has to be placed alongside
a ruler and the length needs to be measured from the tip of the
beak to the end of the middle toe (see picture below). This trait is
often taken in broiler hatcheries as it is well known that the chick
length measured on hatch day can have a signi cant impact on
the performance at the end of the rearing period. For layer type
chicks, this trait is not relevant as the chicks are able to compensate body weight development during the long rearing period of
18 weeks. If the hatchery manager nonetheless decides that the
chick length should be recorded, the gures should be interpreted only in accordance with the hatch window. Layer type chicks
can grow more than 1 cm per day which means that the age of
the chicks at the point of investigation is of crucial importance.
Measuring the length of a chick with a ruler
Measuring feather length
Examining the feather length of a newly-hatched chick can, in addition to other factors, help to optimize the incubation process.
It can give an impression on how fresh the chicks are and if the
incubation time chosen is either just right, too long or too short.
It must be taken into consideration that the feather length varies
between breeds. Fast-feathering chicks (e.g. the female line of the
LB parent stock) already have much longer feathers at the time
of hatch and the growth rate of the primary feather is also higher than in genetically slow-feathering birds. When measuring the
length of a wing feather, a ruler must be placed carefully between
the wing feather and then can the length be recorded. In the hatchery, LSL parent stock chicks show an average feather length of
9.6 mm with an average growth rate of 0.09 mm per hour. LB parent stock chicks, however, already show an average wing feather
length of 15.6 mm which grows at 0.15 mm per hour.
Length of a wing feather
Measuring the feather length of a wing
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