Care must be taken to ensure correct orientation of the eggs when placing them on setter trays
It is important to pay attention to the orientation of the eggs when placing them on setter trays as this has quite an impact on hatch results, both in terms of hatchability and chick quality. Air cell up is the way to go.
The embryo lies on the surface of the yolk and is connected to the latebra (white yolk), which is located in the centre of the yolk. The water-rich latebra has a lower specific gravity than the lipid-rich yolk and, according to the laws of physics, the embryo will always move to the top of the egg … no matter which way the egg is placed on the setter tray.
By about day 14 the developing embryo lies on top of the yolk sac. It then turns so it lies lengthwise in the egg and by day 18 the embryo’s head is under the right wing with the beak pointing upwards, ready to pierce the air cell (internal pipping) and inflate the lungs prior to finally emerging from the egg. But what if the air cell is out of reach of the embryo?
The air cell is situated at the blunt end between the shell membrane and the egg membrane. The egg shell is more porous at this end and therefore air will enter here as the egg contents shrink due to cooling down after laying. During storage and incubation, the air cell gradually increases in size as water evaporates from the egg contents.
When eggs are set accidentally sharp-end-up, the head of the embryo is at the opposite end from the air cell and internal pipping is impossible. It is very difficult for the embryo to hatch in this position because it is fully dependent on the limited oxygen supply through the chorioallantoic membrane, and because the shell is stronger at the sharp end and there is less space for pipping and moving around. Unsuccessful embryos can be recognised during break-out of hatch residue by their legs being near the air cell; however not all eggs that are incubated sharp-end-up fail to hatch.
A customer in Turkey carried out an experiment in 2016 using different breeds and flock ages. 300 eggs were set sharp-end-up and 300 eggs in the normal position. This resulted in 12.7 – 21.0 per cent lower hatch of fertile, mostly due to a difference in late mortality (see figure). Moreover, among the eggs that had been incubated sharp-end-up, there were more culled chicks. When sharp-end-up incubation is combined within-ovo vaccination, the results are even more dramatic. A small-scale experiment conducted by a customer in Hungary in 2019 with 162 eggs per treatment resulted in 93 saleable chicks from sharp-end-up incubated eggs. When eggs in this position were also in-ovo vaccinated, only 39 saleable chicks were obtained. The control group (sharp-end-down and in-ovo vaccination) showed normal hatch results.
Be aware that if 10 per cent of eggs are accidentally set sharp-end-up hatchability will be up to 2 per cent lower.
Train staff in breeder farm and hatchery to set eggs with air cell up (sharp-end-down/blunt-end-up).
Use a candling light in a darkened room to make air cell visible if in doubt.
Consider automated sharp-end-down setting, especially when doing in-ovo vaccination.
Take a sample from setter trays ready for incubation to check for correct setting.
Pay more attention to egg orientation if you notice the ‘legs near air cell’ sign during break-out of hatch residue.
BEST EGG INCUBATOR COMPANY IN NAIROBI, KENYA
When incubating any bird egg it is important to control the same factors of temperature, humidity, ventilation, and egg turning.
Temperature is the most critical environmental concern during incubation because the developing embryo can only withstand small fluctuations during the period. Embryo starts developing when the temperature exceeds the Physiological Zero. Physiological zero is the temperature below which embryonic growth is arrested and above which it is reinitiated. The physiological zero for chicken eggs is about 75oF (24oC).
The optimum temperature for chicken egg in the setter (for first 18 days) ranges from 99.50 to 99.75 o Fand in the hatcher (last 3 days) is 98.50 F.
Incubation humidity determines the rate of moisture loss from eggs during incubation. In general, the humidity is recorded as relative humidity by comparing the temperatures recorded by wet-bulb and dry-bulb thermometers. Recommended incubation relative humidity for the first 18 days ranging between 55 and 60% (in setter) and for the last 3 days ranging between 65 and 75%. Frequently there is confusion as to how the measurement of humidity is expressed. Most persons in the incubator industry refer to the level of humidity in terms of degrees F., (wet-bulb) rather than percent relative humidity. The two terms are inter convertible and actual humidity depends upon the temperature (F.) as measured with a dry-bulb thermometer. Conversion between the two humidity measurements can be made using a psychometric table.Rarely is the humidity too high in properly ventilated still-air incubators. The water pan area should be equivalent to one-half the floor surface area or more. Increased ventilation during the last few days of incubation and hatching may necessitate the addition of another pan of water or a wet sponge. Humidity is maintained by increasing the exposed water surface area.
Ventilation is very important during the incubation process. While the embryo is developing, oxygen enters the egg through the shell and carbon dioxide escapes in the same manner. As the chicks hatch, they require an increased supply of fresh oxygen. As embryos grow, the air vent openings are gradually opened to satisfy increased embryonic oxygen demand. Care must be taken to maintain humidity during the hatching period. Unobstructed ventilation holes, both above and below the eggs, are essential for proper air exchange.
4. Turning of eggs
Eggs must be turned at least 4-6 times daily during the incubation period. Do not turn eggs during the last 3 days before hatching. The embryos are moving into hatching position and need no turning. Keep the incubator closed during hatching to maintain proper temperature and humidity. The air vents should be almost fully open during the latter stages of hatching.In a still-air incubator, where the eggs are turned by hand, it may be helpful to place an “X” on one side of each egg and an “O” on the other side, using a pencil. This serves as an aide to determine whether all eggs are turned. When turning, be sure your hands are free of all greasy or dusty substances. Eggs soiled with oils suffer from reduced hatch ability. Take extra precautions when turning eggs during the first week of incubation. The developing embryos have delicate blood vessels that rupture easily when severely jarred or shaken, thus killing the embryo.
5. Position of eggs
The eggs are initially set in the incubator with the large end up or horizontally with the large end slightly elevated. This enables the embryo to remain oriented in a proper position for hatching. Never set eggs with the small end upward.