International Poultry Production — Volume 23 Number 4 15

by Djanet Ould-Ali, technical specialistAfrica and Robert Schulte-Drüggelte,hatchery specialist, Lohmann Tierzucht,Germany.

The aim of every commercial layerhatchery is a maximum hatchability offirst quality chicks. Only healthy and

vital chicks are able to have a good start inthe rearing period after being handled andtransported. Good chick quality is clear to see with alow first week mortality rate and a uniformdevelopment of the whole flock. It istherefore the key to success not only for thehatchery but also the rearing farm.

The key to success

A first indicator for chick quality is thepercentage of second grade chicks. Thispercentage is naturally influenced by the ageof the breeder flock. Young breeder flocks,for example at <30 weeks, usually givepoorer results. If the chick quality does not improve withthe age of the breeder flock, examinationsneed to be performed in order to find outthe causes. These causes can either be the age of thehatching egg and the general quality of thesame, transport and storage conditions aswell 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 ofturning during incubation.The evaluation of chick quality in thehatchery provides important information onthe whole production process. If properlyapplied, it can be used to detect possibleweaknesses of the hatchery and the workingroutines in the same. Either quantitative orqualitative traits can be used for themeasurement of chick quality.The qualitative traits are namely chickweight, chick yield, chick length and featherlength. Qualitative traits include the vitality

of the chicks, the quality of their navel, theirbeaks and joints.Many hatcheries still hesitate to apply theexamination of the qualitative traits in theirquality monitoring program as these traitsare highly subjective and hardly reliable.There are, however, methods that canhelp to measure the qualitative traits asobjectively as possible, i.e. by reducing theindividual subjectivity to a minimum.These so-called ‘scoring’ systems enablerecordings of the first visual quality traits of achick to be transformed into a quantifyingassessment with a maximum score of 10points. For every negative factor, one pointwill be deducted from the total of 10 points.Parameters that can be included in thescoring system are all of the above-mentioned qualitative traits as well asadditional factors, for example the efficiencyof vaccination and injuries. This can help tomonitor and improve the chick processingquality.

Investigating chick quality

The point of investigation should bedetermined by the aim of the qualitycontrol. If these investigations serve theprimary purpose of improving internalproduction processes, then chick qualityshould be investigated at takeoff. The

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Review of different day-oldchick quality parametersin layer type breeds

Left, recording single chick weight atthe hatchery and, below, weighing acertain number of chicks. Do not forgetto subtract the weight of the hatcherbasket before calculating the averagechick weight.

Left, an example of a poor quality navel and right, a good quality navel.

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advantage of this is that at this point of theproduction chain, an overview of the qualityof all hatched chicks can be attained. Thishelps to make conclusions about theincubation process and can give importanthints on what needs to be improved.If it is desired to get an overview about thequality of the chicks that will be handed overto the customers, and if information aboutthe sorting and handling of the chicks arejust as required, then it can be moreappropriate to conduct the examinationsbefore transporting the chicks. At this point, the quality of the vaccinationand chick handling can be evaluated as well.

Chick weight

Chick weight is highly correlated with eggweight and therefore relatively predictable.If the incubation process is done properly,the chick weight will be two thirds of theegg weight. An extended or reduced incubation timeas well as too high or too low temperaturesand humidity levels during incubation canalso have an impact on chick weight. The longer the chicks stay in the hatcher,the more weight they will lose due todehydration. On the other hand, if the

chicks are pulled early, the chick weight canbe higher than expected. Two methods canbe used for measuring chick weight: l Take single chick weights of a certainnumber of chicks. This allows the variationof chick weights within the groupinvestigated to be calculated in addition tothe average. A good or bad uniformity ofchick weight can be used as an indication ofthe quality of hatching egg grading. l The other possibility is to weigh a certainnumber of chicks at one time and calculatethe average. This is a good and simplemethod, i.e. if only the average chick weightis of interest.

Chick yield

In relation to chick weight, the quantitativetrait ‘chick yield’ (chick weight at hatch in %of the egg weight at point of set) must bementioned. This is a simple method of checkingwhether the hatch time and incubationparameters are correct. To accurately measure chick yield, it isimportant to measure the weight ofcompletely filled setter trays at the point ofsetting and to calculate the average eggweight (do not forget to subtract the weightof the empty setter tray before calculatingthe average egg weight). The weighed setter trays must be labelledin order to identify them on the day oftransfer. On the day of hatch, the chickswhich originate from these labelled settertrays must be weighed in order to calculatethe average chick weight.The ideal chick weight should be between66-67% of the egg weight. If the chick weightis below target, this can be an indicator thatthe chicks were pulled too late and aretherefore at the risk of dehydration. It canalso be a sign that the humidity level chosenduring incubation was too low.If chicks are required to travel longdistances, it can be appropriate to aim for achick yield which is about 1% higher than theideal of 66-67%. This can help to guarantee

that the chicks arrive as fresh as possible atthe rearing farm. In order to achieve reliable results in termsof chick yield, at least 70 eggs and 70 chicksper breeder flock must be weighed. It willsurely be more accurate if from every flock,three setter trays in different positions in thesetter are investigated.

Chick length

In addition to chick weight and chick yield,the length of the chicks is anotherquantitative trait which can be recorded inthe hatchery.In order to measure a chick, it has to beplaced alongside a ruler and the lengthneeds to be measured from the tip of thebeak to the end of the middle toe.This trait is often taken in broilerhatcheries as it is well known that the chicklength measured on hatch day can have asignificant impact on the performance at theend of the rearing period.For layer type chicks, this trait is notrelevant as the chicks are able tocompensate body weight developmentduring the long rearing period of 18 weeks.If the hatchery manager nonetheless decidesthat the chick length should be recorded,the figures should be interpreted only inaccordance with the hatch window. Layer type chicks can grow more than 1cmper day which means that the age of thechicks at the point of investigation is ofcrucial importance.

Measuring feather length

Examining the feather length of a newly-hatched chick can, in addition to otherfactors, help to optimise the incubationprocess. It can give an impression on howfresh the chicks are and if the incubationtime chosen is either just right, too long ortoo short. It must be taken intoconsideration that the feather length varies

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Investigating chick activity.

Left, measuring the feather length of a wing of a Lohmann LSL chick and, right, measuring the length of the chick with a ruler.

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between breeds. Fast-feathering chicks (forexample the female line of the LB parentstock) already have much longer feathers atthe time of hatch and the growth rate of theprimary feather is also higher than ingenetically slow-feathering birds.When measuring the length of a wingfeather, a ruler must be placed carefullybetween the wing feather and then thelength can be recorded.In the hatchery, LSL parent stock chicksshow an average feather length of 9.6mmwith an average growth rate of 0.09mm perhour. LB parent stock chicks, however,already show an average wing feather lengthof 15.6mm which grows at 0.15mm perhour.

Chick vitality

Chicks of premium quality must be lively andhave a good body tension. This can bechecked by placing a day-old chick on itsback. A good chick does not struggle to get backdirectly on his feet. One can say that itshould not take more than three secondsfor the chick to get back in an uprightposition.

Navel

An essential element in investigating chickquality is examining the quality of the navel.A good navel is closed, dry and free of eggshell and membrane residues. The chick needs to be handled manually tocontrol the quality of its navel. Of course, itis not possible to check every chick in acommercial hatchery prior to delivery.

Beak and joints

Investigating the condition of the beak andjoints of the chicks can give several hints onincubation conditions. Both must have a

normal appearance which means they haveto be free of damage and wounds.Wounded beaks and joints are hints of non-optimal conditions in the hatcher.Red dots on the beak indicate that the

temperature in the hatcher was too high.Either the chicks wanted to break out of theegg shell too fast and damaged their beak byworking too hard on the egg shell or theytried to regulate their body temperature bybreathing through the openings of the hatchbasket. By doing so, they damage the upperpart of their beaks.Injured joints can be a sign of a very highhumidity level during incubation. Chickswhich are hatched under these highhumidity conditions must put in more effortto break out of the shell, which then harmstheir joints.

Investigating belly quality

The belly of day old chicks must be soft andsmooth. Bloated, stiff and hard bellies aresigns of a badly absorbed yolk.This often leads to problems duringbrooding and results in a higher first weekmortality rate.Causes for big and hard bellies in layertype chicks might be due to both insufficientwater loss and too high temperatures duringthe incubation process. A hard belly is also asign of a yolk sac infection.

Evaluation of data

The collection of data can be done bymeans of written forms and/or can bedirectly entered into a computer program.A good practice is to collect the data basedon breeder flock and hatch day. This aids anoverview on performance fluctuationsrelated to breeder flocks and/or to hatchday or even season of the year.Of course, data collection only makessense if one is able and willing to search for

the causes for obvious differences in chickquality. Only this can help to improve theproduction process.

Summary

The aim of every hatchery is to achieve thehighest possible number of premium qualitychicks. To get an idea on the quality ofproduced and ready to sell chicks, it makessense to collect data of chick quality usingclearly defined parameters. These parameters can be both quantitativeand qualitative traits. Quantitative traits arenamely chick weight, chick yield, chick andfeather length. Qualitative traits are more subjective andinclude the investigation of chick activity andthe quality of the navel, beak and joints.There are methods which can help tomeasure the qualitative traits as objectivelyas possible to achieve a reliable overviewabout the produced chick quality. n

References are available from the author on request

Left, a badly absorbed yolk (big and stiff belly) and, right, a well absorbed yolk (softand smooth belly).

Red dot beak. Wounded joints.

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