Long term success in hatchery management depends on having the right tools and techniques to monitor the requirements of both the egg and developing chick as well as having properly trained staff who can measure, react to and satisfy those requirements
Despite huge on-going advances in modern technology, best tools available to hatchery workers are still their own observations and instincts through human senses of sight, hearing and smell. Prompt initial identification of any problem relies on individuals recognizing warning signs and accepting that there is now a pressing need to investigate. This is where the new technology comes in as a support mechanism which allows the hatchery worker to fine-tune the whole incubation process.
Possessing the knowledge to identify and act on outstanding issues is also essential. This is the view of Dr Nick French, Incubation Specialist at Aviagen which has recently enhanced and extended its range of technical literature covering the all-important key areas of egg incubation and on which this article is based.
Key areas of egg incubation are:
- The temperature of the embryo during incubation of the egg
- Water loss from the egg throughout incubation and chick yield
- Correct incubation time for the specific poultry breed and product
Embryo temperature – monitoring and taking stock
Temperature of the embryo is the key and crucial trait of egg incubation and closely related to temperature of the eggshell. This can be easily measured in a completely non-destructive way and without causing any harm to the embryo. Using eggshell temperature as a ‘marker’ for embryo temperature is essential because temperature within the incubation machine will not, and cannot, give an exact and accurate prediction of embryo temperature.
All that is required is an infra-red thermometer such as the Braun Thermo Scan 4520. With the temperature of the eggshell successfully measured, the operator now has an accurate guide for temperature of the embryo itself. Eggshell temperatures must be measured at the equator of the egg because over the air-cell the reading will register lower than the true embryo temperature. Operators must make sure they are using eggs with live embryos because an infertile egg does not generate heat.
Once the eggs have been monitored for temperature it is time to collate and interpret the data. Use of thermal imagery shows how temperature can vary across the range of eggs in a single tray, including increased heat in the eggs in the centre of the tray, as well as the inherent occurrence of a relatively lower temperature above the air cell.
Optimum embryo temperature for ideal hatchability and chick quality is between 37.5°C and 38.3°C. Temperatures in excess of 39°C may prove dangerous and the middle period of incubation is especially critical and sensitive because there is a well-established risk to the embryo if temperatures rise even slightly above 38.3°C. Delayed hatch may be the consequence of temperatures which are too low (i.e. below 37.5°C).
Acting on the information received
Firstly, operators should make sure the incubation machine is working correctly with temperature probes calibrated correctly and all fans working properly. If, under single-stage conditions, the temperature is too high or too low at any stage during the incubation period operators should make small incremental adjustments to the temperature programme to bring the eggshell temperatures into the correct range.
With a multistage 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 warm or the eggs at the beginning are too cool. After checking the operation of the machine, make sure that the multistage loading pattern is correct.
Since multistage machines will hold eggs at different stages of incubation only one single temperature setting applies to all of the eggs. This means that it may be necessary to ‘negotiate’ a compromise between the requirements of the eggs at the start of incubation and those at the end of incubation. Where possible, operators should adjust settings to keep egg temperatures out of the danger/delay area at all times.
Uniformity of incubator temperature
As with the checking of eggshell temperature against setter temperature, it is equally important, indeed crucial, to ensure that temperatures across the incubator are uniform. This can only be achieved by making regular and exhaustive checks on egg temperature. The objective of such testing 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. Do not monitor the eggs in the very top or bottom trays but do monitor eggs in the centre of the tray because these will be warmer than the eggs at the edges.
Maintaining optimum humidity
The second important consideration during egg incubation is the 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. Around 11 per cent to 12 per cent of egg weight is typically lost in this way during chick development. The actual rate of loss depends on the definitive porosity of the eggshell the humidity of the air within the incubator.
Maintaining the right humidity in the setter is crucial to a successful hatch. 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 from 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 cannot happen, too big and the embryo will desiccate.
Ideal method to ensure humidity levels are correct is to weigh the eggs at the start of incubation and then re-weigh them at 18 days. Weight of water lost is calculated by subtraction and finally expressed as a percentage of the initial egg weight. If that percentage is outside the 11-12 per cent range then the humidity requires adjustment.
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