Jessie Taylor
Candling is a method used in embryology to study the growth and development of an embryo inside an egg. It involves shining a light source, typically a bright and focused beam of light, through an eggshell to observe the internal contents of the egg. This technique can be used to assess the quality and development stage of an egg. It is a commonly used process in commercial hatcheries to assess the fertility and development of eggs, particularly during the incubation period. The original sources of light used for candling were candles, hence the name. Today, various lighting tools are available for candling, such as the Cool-Lite Tester, which helps reduce the risk of damaging the delicate eggshell.
| Characteristics | Values |
|---|---|
| Definition | "Candling is the age-old method of looking inside an egg — without breaking it open — and figuring out what’s going on inside." |
| Purpose | To determine if a viable embryo is inside and to check the development of the baby chick, as well as to determine the quality of the eggs for human consumption. |
| Timing | Candling can occur at various intervals, including before incubation, and 6-8 days, 7 days, 8 days, 9 or 10 days, 10 days, 11 days, 14 days, and the last few days of incubation. |
| Equipment | A light source, such as a candle, light bulb, flashlight, or specialized candling device like the Cool-Lite Tester. |
| Process | The egg is placed in a dark or dimly lit room, with the light source positioned behind it to illuminate the contents and allow for observation of indicators such as veins, blood vessels, air pockets, and embryo movement. |
| Benefits | Candling helps identify infertile or non-viable eggs, detect early mortality, optimize incubator space, reduce contamination risks, improve hatchery efficiency, and contribute to higher hatch rates and healthier chicks. |
| Drawbacks | Potential for candling errors, especially with certain equipment and high numbers of 'clears' (infertile or non-viable eggs). |
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What You'll Learn
Candling equipment and tools
The process of candling involves using a bright light source to illuminate an egg, allowing for the study of the growth and development of an embryo inside without breaking the egg open. The technique is used in the egg industry to assess the quality of eggs for human consumption and to determine the presence and viability of an embryo.
Light Sources:
- Modern LED Torch: Rechargeable, ultra-bright LED torches are recommended for candling. These torches provide consistent brightness over time, unlike traditional LED torches with batteries that tend to dim as the batteries age.
- Titan Egg Candling Device: This device is a tabletop unit with a designated spot to place the egg. It offers hands-free operation and convenience.
- Candles: In traditional candling, candles were used as the light source, placed inside a wooden box with a hole for the egg. However, candles are less commonly used today due to fire risks.
Power Sources:
- Mains-powered candling devices: Some egg candlers are designed to be plugged into an electrical outlet for power.
- Battery-operated candlers: These devices use batteries as a power source and may be more portable and versatile in certain situations.
Incubators:
Incubators are essential for maintaining the appropriate temperature for eggs during candling. Modern LED lights produce less heat, reducing the risk of overheating the eggs. It is crucial to avoid disturbing the eggs unnecessarily and to maintain proper incubation conditions.
Darkened Room:
A darkened room is recommended when candling eggs. By turning off the lights and reducing external light sources, the shadows and details within the egg become more visible when using the candling light source.
It is important to invest in quality candling equipment, as cheaper options may have inferior seals between the light source and the egg, impacting the effectiveness of the process. Additionally, proper candling techniques and regular intervals (such as after 7 and 14 days of incubation) are crucial for accurate assessments of egg quality and embryo development.
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Embryo development
The development of a chick embryo is a complex process that occurs over a brief three-week period. Before an egg is laid, fertilisation occurs, followed by the division and growth of living cells, which then segregate into groups of special functions, or tissues. Once an egg is laid, embryonic development is paused until proper cell environmental conditions are established for incubation to resume.
During the first day of incubation, the first signs of resemblance to a chick embryo appear after 16 hours, with the emergence of the alimentary tract, vertebral column, nervous system, head, and eye. By the second day, a third layer of cells, the mesoderm, forms between the ectoderm and endoderm layers. This is significant as it marks the beginning of the development of vital organs, including the heart, ear, eye, and brain. The ectoderm produces the nervous system, parts of the eyes, feathers, beak, claws, and skin, while the endoderm produces the respiratory and digestive systems, as well as secretory organs.
By the third day, veins have developed, allowing the embryo to access nutrients from the egg's external membranes. Voluntary movements of the embryo can occur from day six, caused by the force of its rapid heartbeat of 260 to 280 beats per minute. On day seven, digits begin to appear on the feet and develop into toes, and feather germs form on the tail. By the end of day seven, the embryo will look more like a bird, with all the main parts of a chicken present.
On day nine, the yolk takes on a flatter form, and the albumen separates into two layers that surround the top and bottom, cushioning the growing embryo. The egg tooth, which the chick will use to break through the eggshell, grows larger, and the beak lengthens and hardens. By day 14, the embryo positions itself for hatching, turning its head towards the large end of the egg, where it will soon break free. From day 15 onwards, incubation focuses on finalising the embryo's development, hardening its bones, claws, skull, and leg scales, and drawing the small intestine into the abdominal cavity.
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Fertility assessment
The primary objective of egg candling in fertility assessment is to identify infertile eggs that do not contain embryos and, therefore, will not hatch. These eggs can be removed from the incubation process, conserving resources and preventing the unnecessary use of incubation space and energy. This practice also helps maintain hatchery efficiency by reducing the risk of contamination from decomposing embryos.
During the candling process, workers look for specific indicators to determine fertility. After about a week of incubation, a fertile egg will typically display a dark dot, representing the embryo, along with spider-like veins stretching out around the egg. In some cases, the embryo may be more challenging to observe, and it could be located in the centre or on the opposite side of the egg. Rotating the egg can help in getting a better view.
It is important to note that candling should be done gently, with the pointed end of the egg facing downwards, to avoid damaging the embryo. Additionally, eggs should be kept outside the incubator for only a short period during the candling process, as the embryo's heart rate can be affected by temperature changes.
Through regular fertility assessments using egg candling, hatcheries can improve the overall quality of hatched chicks. By removing non-viable eggs and identifying potential issues, hatcheries can achieve higher hatch rates and promote the health and well-being of the chicks. This process also aids in waste reduction, as infertile or non-viable eggs can be utilised for other purposes, such as pet food production.
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Optimal candling times
If the purpose of candling is to check the quality of eggs for human consumption, one must examine the egg's air cell, the yolk, and the albumen or egg white. This process determines whether the egg should be graded AA, A, B, or inedible.
It is important to note that candling should not be done during the first few days of incubation as this is the most critical period of embryo development. Similarly, candling is not recommended during the last few days of incubation as the chick moves into position to hatch.
To ensure optimal candling results, it is recommended to use a reliable and bright light source, such as an ultra-bright LED torch or the Titan Egg Candling device. Additionally, it is important to maintain the temperature of the egg during the process and to ensure that the eggs are not out of the incubator for an extended period.
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Benefits of candling
Candling is a method used in embryology to study the growth and development of an embryo inside an egg. The process involves passing a bright beam of light behind an egg in a darkened room to reveal details about its contents. The original sources of light used were candles, hence the name.
Fertility Assessment
Candling helps identify infertile eggs that do not contain developing embryos. These eggs will not hatch and can be removed from the incubation process, preventing unnecessary use of incubation resources.
Early Mortality Detection
Eggs with embryos that have died at an early stage can be identified and removed, preventing potential contamination from decomposing embryos. This allows hatcheries to allocate resources more effectively to viable eggs.
Hatchery Efficiency
By identifying non-viable eggs early on, hatcheries can optimise incubator space, reduce contamination risks, and improve overall efficiency.
Chick Quality
Candling can help improve the quality of hatched chicks by removing non-viable eggs and identifying potential issues. This contributes to higher hatch rates and healthier chicks. It also helps estimate the expected percentage of viable chicks.
Data Collection and Analysis
Hatcheries can gather data on hatch rates, fertility rates, and other metrics by tracking candling results over time. This information is valuable for evaluating hatchery performance and making necessary adjustments.
Waste Reduction
Removing non-viable eggs reduces waste and the need for disposal. In some cases, these eggs may have alternative uses, such as for pet food or other products.
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Frequently asked questions
Candling is a method used to study the growth and development of an embryo inside an egg. It involves using a bright light source behind the egg to show details through the shell.
Companies candle eggs to assess the quality of the eggs for human consumption. It also helps to identify infertile eggs that do not contain developing embryos, allowing companies to remove them from the incubation process and prevent unnecessary use of resources.
Companies typically use modern lighting tools such as the Cool-Lite Tester from GQF Manufacturing, which minimizes handling time and provides a tight seal against the base of the egg to reduce escaped light.
