Candling

Candling

Candling allows you to see which eggs are infertile, contain dead embryos, or are viable. For example, you can carry out candling with a breakout analysis, at four fixed ages in each parent stock flock (in each house). This will generate a lot of valuable management data, which can help breeder farms and hatcheries. But you must analyse and use this data to create your own hatchery specific reference data. This will give you insight into all the details: the breed, feed used, nest type, feeding system, lighting, ventilation in relation to fertility, hatchability percentage, and chick quality. So, you have a wealth of information! • Candling on day 2 is mainly used to determine the rate of fertilisation, e.g. in young flocks. • Candling on day 10 is not standard practice, and it primarily provides a picture of early embryo mortality. It might be used more Caution! often in the future if in-ovo sexing gains in popularity as a practice in the layer production Clear eggs are not all infertile. You need to breakout an egg to determine whether it is sector. In this case, you would only transfer infertile or an early embryonic mortality. pullets, and would be able to remove infertile eggs and dead embryos immediately. • Candling on day 18 is the most practical method because it allows you to remove infertile eggs, eggs that contain dead embryos, and, above all, rotten eggs, so the chicks that hatch will not be contaminated. However the data gained from candling at this time can no longer be used to influence the process.

Breakout image at 2 days

Good hatching egg, fertile Infertile egg

So, the timing of candling depends primarily on the goal. The blood ring stage is one example of a critical moment in the incubation process. If something has gone wrong in the breeder house, in storage, or during transport, you often see the effect reflected in increased mortality on day 3. If eggs with dead embryos have been in the incubator for a prolonged period, it is increasingly difficult to pinpoint the precise time of death. Candling during the process creates more moments to provide feedback to the breeder farm. It also helps you identify the moment a problem starts more accurately. If you only candle on day 18, and you include the storage duration in your calculations, you are already 3 weeks too late to make any changes in breeder flock management. Maintain a constant temperature Ensure the ambient temperature is at least 25°C/77°F during candling. If you want to put the eggs back into the incubator, make sure the handling time for candling does not exceed 30 minutes per trolley.copyright protected

4 mm 2 mm

You can recognise a good hatching egg by the round, doughnut-shaped embryo. You see a white, symmetrical ring (area opaca) with a clear core (area pellucida). Sometimes, you see a little white point in the centre. This is larger than it is in an infertile egg. You recognise an infertile egg by the imperfectly round shape of the embryo, with a jagged edge. Usually, multiple bubbles joined together. You see a little, compact, white point, sometimes slightly grainy.

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Fertile: the germinal disc always has a rounded, doughnut shape and a white symmetrical ring with a clear centre point, sometimes with the white dot in the middle. Infertile: the germinal disc is almost never perfectly round, has a jagged edge, and a very tiny white point.

Candling/breakout analysis after day 2

Eggs are sometimes manually candled on day 2 in the setter. You use a separate incubator for candling on day 2, so that you do not disrupt the incubation process of the main batch. The incubation conditions in this incubator are not so important because your only goal here is to determine whether the eggs are fertile or not. This is mainly done with young flocks that have just come into production. So, this is not standard practice for every delivery of hatching eggs. Early candling gives you the advantage of being able to respond in good time to infertile eggs or those with early mortalities. You can predict the hatchability and use this to plan your sales. This ensures that you will not disappoint a customer by supplying too few chicks. You have to breakout the eggs to differentiate between infertile eggs and those with early embryonic mortalities because this can only be detected by candling from 3 days onward (the blood ring stage). And, in cases where development is slightly delayed, e.g., in eggs that have been stored for a longer period, this can easily be a day later. This does not apply to brown eggs in the layer sector (thicker eggshell and the brown shell limits how much light shines through the eggs). Candle 450 eggs per house. This makes it workable. It helps to train 1 or 2 people and make them available to carry out these types of measurements and observations.

Candling after 10 days

Tenth-day candling is a standard practice in hatcheries for parent or grandparent stock. This is not usually done for every batch at a commercial hatchery that produces broilers or laying hens. Tenth-day candling is often carried out twice for each flock, at about 30 and 40 weeks of age. At about 10 days, 750 eggs per house are candled. Often, there are 150 eggs on each setter tray, so you select 5 random trays. Note where you take each tray from, so that you can link any differences in the trays to their positions in the incubator. If there is no visible embryo with candling, you break the eggs in question (perform a breakout analysis) on the tray, to score them and determine the cause. The goal of tenth-day candling is to make the link between the house, farm, housing system, and feed company. If candling is standard practice, you can collect data and recognise patterns and tendencies that are specific to each poultry house. Hatchability can no longer be improved at this stage, the primary purpose here is to gain more insight into the process. Insight into future hatchability can also be important for the hatchery’s planning. copyright protected

A day 10 candling image of a fertile egg. You can recognise a fertile egg by the dark patches. To discover the day on which an embryo died, you need to carry out a breakout analysis, to see the embryo’s stage of development. You cannot see this properly with candling. A full breakout at day 6. Here all dead embryos and unfertile eggs are set aside for later counting.