Despite advances in modern technology, the best tools available to hatchery workers remain their own sense of sight, hearing and smell. Initial identification of a problem is down to individuals recognising the warning signs and acknowledging the need to investigate. Technology is then used as a support mechanism, allowing the hatchery worker to fine tune the incubation process.
Of course, having the knowledge to identify and resolve issues is also important. Aviagen has recently enhanced its range of technical literature, and that literature and this article cover the key areas of incubation, including:
• The temperature of the embryo during the incubation
• Water loss of the egg through incubation and chick yield
• Correct incubation time for the breed and product
Whilst not a definitive guide, the information included below should be of use to any hatchery worker or manager, however, it is important to check with your local technical manager if you are unsure of any of the advice given here.
Taking stock of temperature
The key trait is the embryo temperature during incubation. This is closely related to the egg shell temperature, which can be measured easily and without harming the embryo.
Machine air temperature will not exactly predict embryo temperatures.
Checking eggshell temperature
The only tool needed to do this is an infra-red thermometer, such as the Braun ThermoScan 4520. The egg shell temperature is an accurate guide for the temperature of the embryo itself.
Eggshell temperatures must be taken at the equator of the egg (image 1), because over the aircell the reading will register lower than the true embryo temperature. Use eggs with live embryos as an infertile egg will not be producing heat.
Analysing the data
Once the eggs have been monitored, interpret the data. The thermal image below (image 2) shows how temperature can vary across eggs in a single tray, and the relatively lower temperature above the air cell. Note the increased heat for the eggs in the centre.
The ideal embryo temperature for hatchability and chick quality is between 37.5°C and 38.3°C (99.5°F and 101°F). A temperature above 39°C (102°F) can be dangerous, although in the middle period of incubation there is an increased risk to the embryo if temperatures rise even slightly above 38.3°C (101°F). If the temperature is too low (below 37.5°C (99.5°F), this could result in a delayed hatch.
The graph below (figure 1) highlights the different areas of risk. Note that the high temperature risk area changes with incubation stage.
Acting on the information
Firstly, make sure the machine is working correctly, temperature probes are correctly calibrated and all fans are running properly. Under single-stage conditions, if the temperature is too high or too low at any stage during the incubation period, make small incremental adjustments to the temperature programme to bring the eggshell temperatures into the correct range.
With a multi-stage setting, there is less scope for making adjustments and the most likely situation is that either the eggs at the end of incubation are too hot or the eggs at the beginning are too cool. As well as checking the operation of the machine, double-check the multi-stage loading pattern is correct.
Because multi-stage machines have eggs at different stages of incubation only one temperature setting applies to all the eggs. This means it may be necessary to make a compromise between the requirements of the eggs at the start, and those at the end, of incubation. Settings should be adjusted to keep egg temperatures out of the danger/delay area at all times, but it may be inevitable.
Checking uniformity of incubator temperature
As with checking the eggshell temperature against setter temperature, it is also important to make sure that temperatures across an incubator are uniform. It is vital to make regular checks on egg temperature.
When testing, the objective is to sample eggs from locations on the left and right, front and back and top, middle and bottom of the setter. The exact locations will vary with machine design, but all areas of the setter should be sampled.
Don’t: Monitor eggs in the very top or bottom trays.
Do: Monitor eggs in the centre of the tray; these will be warmer than the eggs at the edges.
The second important consideration is humidity. Maintaining the right humidity in the setter is crucial to a successful hatch as it controls the amount of water lost from the egg during incubation.
Eggs lose water because they have porous eggshells. Typically, around 11 to 12% of the egg weight is lost through this method as the chick develops. The actual rate of loss depends on this porosity and also the humidity within the incubator.
Different egg types will lose different amounts of water and flock age, breed and shell quality will also affect the rate of water loss. It is therefore important to adjust incubation conditions accordingly to optimise water loss from the egg.
Water loss in an egg allows the air cell to form, which gives room for air sac inflation when the chick is about to hatch. Too small and this can’t happen, too big and the embryo will desiccate.
The best method to make sure humidity levels are correct is to weigh the eggs at the start of incubation and then re-weigh them at 18 days. Calculate the weight lost, and express it as a percentage of the initial egg weight. If that percentage is outside the 11-12% range, then adjust the humidity. Otherwise hatchability can be affected as shown in figure 2.
Chick yield is a measure of how hydrated the chick is at hatch – it is the chick weight expressed as a percentage of the initial egg weight. The optimum percentage yield should be between 67 and 68%. Lower than this and the chick is likely to be dehydrated with little yolk reserve, which shows up as active and noisy behaviour. Higher than this and the chick is likely to be lazy and won’t perform well on the farm.
Formula for working out chick yield:
Percentage Chick Yield = Average chick weight divided by Average egg weight at set x100
The common causes of low chick yields are incubating the eggs too long, low humidity or a high temperature. Conversely, high yields are produced by too short an incubation period, low temperature or high humidity.
Importance of hatch timing
All the hard work done in ensuring optimum temperatures and humidity levels are correct can count for nothing if hatch times are not correct. Removing chicks from the hatcher too early can result in some loss of hatch and/or with immature chicks on the farm, which won’t perform well and may be susceptible to disease.
Holding chicks in the hatcher for too long also brings problems. Often the chicks will overheat, leading to poor yolk reserves, dehydration and ultimately, poor broiler performance.
There are a number of indicators of incorrect hatch timing. There should be a maximum of 2% chicks per tray hatched around 30 hours ahead of the expected take-off time. More than that means the incubation time is too long and future hatches should be delayed by the appropriate amount.
Also look for!
• Meconium stained shells in the hatch debris mean the chicks have been out too long.
• Dampness on the back of the neck should be visible in around 5 per cent of chicks at take-off if timing is correct.
• If the feather blade has formed at hatch time, the incubation time was too long.
Adjust set times safely in 3 hour increments up to a maximum of 15 hours. Do not adjust temperatures but do keep checking to make sure the adjusted time is correct.
Why collect this data?
Carrying out regular, thorough checks will help eliminate problems and make any investigations much quicker. All hatchery staff should be trained to spot the potential issues outlined above, and use the data collected to make informed decisions.
Data should be collected on:
• Eggshell temperature
• Egg water loss
• Chick yield
This information can give a clear idea of what is happening in the hatchery and enable any necessary action to be pinpointed. The quicker information is gathered and acted upon, the quicker a successful hatching programme can be implemented.
Monitoring performance means improving performance which means taking action. The result? Improved chick output and performance on the farm.