Storey's Guide to Raising Chickens (74 page)
Read Storey's Guide to Raising Chickens Online
Authors: Gail Damerow
By fidgeting in her nest and adjusting eggs with her beak, a setting hen periodically turns each egg beneath her. Constantly adjusting her eggs may make the hen more comfortable or perhaps offers some psychological benefit. The hen can’t possibly know that by turning each egg she keeps its yolk centered within the white and that if an egg isn’t turned, its yolk will eventually float away from the center and stick to the shell lining.
To imitate the hen’s activities, some incubators have automatic turning devices that tilt the eggs from side to side at regular intervals, every hour or every 4 hours. Whole shelves may tilt from one side to the other, or rows of eggs within racks may tilt back and forth.
The first time you use a tabletop, you may find that as the eggs turn some of them get crushed by hitting the fan housing or the switching mechanism in the cover. Mark the positions of those trouble spots in the racks so you can avoid using them in the future. Or get an expansion ring, if one is available for your model, to place between the base and lid to give the eggs a little more room.
Some incubators, especially budget still-air units, don’t have a turning device. Price may be an important consideration in deciding whether or not to get an incubator without a turning device, but your time may be of equal concern. Without a turner, you’ll need to be on hand at least three times a day, every day, to turn the eggs yourself.
For manual turning, if your incubator comes equipped with a rack, simply flip the eggs from one angle to another. If the eggs lie flat on a tray, to make sure you’ve turned each egg place an X on one side and an O on the opposite side with a grease pencil or china marker. Some folks prefer a soft (number 2) pencil, but I stopped using a pencil after I pierced a few shells.
Pipping — the appearance of the first hole in the shell — is a sign that a chick is about to hatch.
Whether the eggs are turned automatically or manually, they aren’t turned end for end, but side to side. Throughout incubation, the pointed end of the egg should never be oriented upward. Otherwise, according to research at the University of Georgia, fewer chicks will hatch, and the ones that do hatch will be of lower quality.
Signs of improper turning are early embryo deaths due to stuck yolks, and full-term chicks that fail to pip, or break through the shell. Eggs need not be turned after the fourteenth day of incubation and should not
be turned during the last 3 days before the hatch, when chicks need time to get oriented and begin breaking out of their shells.
Developing embryos use up oxygen rather rapidly, while at the same time generating carbon dioxide. An incubator therefore needs a good airflow to constantly replenish oxygen and remove the carbon dioxide. All incubators have vents to admit fresh air and expel the stale air.
Some small incubators rely on gravity to let warm, humid air escape through vents in the cover, which in turn causes fresh air to be drawn in through vents in the bottom. Other units have a built-in fan to circulate the air. Although a fan-ventilated (or forced-air) incubator costs more than a gravity-ventilated (still-air or natural-draft) incubator, the steady circulation of air helps maintain a more uniform temperature throughout the incubator, resulting in a better hatch rate.
In tabletop models the fan is usually in the cover, so when you remove the cover, you move the fan away from the eggs. Cabinet models usually have the fan at the top or back of the cabinet and should have a switch that lets you turn off the fan before you open the door. A model that lacks such a switch must be powered down before the door is opened, to prevent the fan from blasting cool air across the warm eggs.
Except for its blades, the fan of a commercially made incubator is sealed so it can’t get gummed up by fluff and other hatching debris. Nevertheless, whenever you clean your incubator, brush off the fan with a soft-bristle paintbrush, then gently pass a vacuum hose over it to suck out fluff.
The normal body temperature of a hen is about 103°F (39.5°C). You’d think that would be the temperature at which an incubator should be run, but other factors figure in. For one thing, the hen’s body does not surround the eggs beneath her, resulting in a slightly cooler temperature for the eggs. Furthermore, an incubator’s thermometer is not necessarily positioned to read the temperature at the position of the eggs. As a result, operating temperatures recommended by incubator manufacturers vary slightly from one model to the next.
A typical operating temperature for a forced-air incubator is 99.5°F (37.5°C); for a still-air incubator, 102°F (39°C). Lethal temperatures are 103°F (39.5°C) in a forced-air incubator, 107°F (41.7°C) in a still-air incubator. The recommendations given in the incubator’s operating manual should be considered baseline; you can improve your future success by making minor future adjustments based on past hatching records.
An incubator with an electronic thermostat is preset by the manufacturer and should need little or no tweaking. Some digital incubators include a readout that will tell you if the room temperature outside the incubator is too hot or cold for the incubator to maintain proper internal temperature.
Even a high-tech electronic incubator may have as a backup an old-fashioned
ether wafer thermostat
, a metal disk filled with ether. When the incubator heats up, the ether expands, causing the wafer to swell until it makes contact with a button switch that turns the heat off. As the incubator cools down, the ether contracts until the wafer loses contact with the switch, causing the heat to go on again.
Compared to an electronic thermostat, the cycling of a wafer against the thermostatic switch allows greater temperature fluctuations — as much as two degrees above or below the desired incubating temperature. A wafer thermostat also typically takes longer to bring the temperature back up after the incubator has been opened.
Regulating the heat in an electronic incubator is done with touch pads or touch buttons. Regulating a wafer involves turning a control bolt to adjust the temperature at which the wafer makes contact with the switch. Most wafer-controlled incubators have an indicator light that goes on when the heat is on and off when the heat is off. After a while, you develop a sixth sense that makes you feel uneasy if the light stays on or off for too long.
Sometimes a wafer goes out, or ceases to function properly, because it springs a leak and the ether escapes. In that case the switch remains in the on position, causing the temperature to stay too high for too long. Unless you catch it right away, the eggs will cook. If your incubator uses a wafer, always keep at least one spare wafer on hand.
A failure of the thermostat, whether it is electronic or wafer controlled, is not the only thing that can cause the incubator’s temperature to soar. The incubator could be too close to a heater, for example, or sunlight could fall on the incubator during part of the day. Even just a short-term rise in temperature does greater damage than a drop, which may occur if the incubator’s cover or door is left ajar, hatching fluff jams the wafer switch, a child or pet pulls the plug, or the power goes out.
The more often you check the temperature, the more likely you are to catch and correct problems such as a pulled plug or a wafer gone bad. During my early years using an incubator, I kept a piece of paper nearby on which I recorded the time and temperature every time I passed the incubator. After a while checking got to be a habit, and I no longer needed the paper reminder. But keeping one nearby is a good idea if two or more people share responsibility for maintaining the incubator.
Some cabinet incubators have an alarm that sounds or lights up when the temperature drops or rises past a certain range. If you’re handy with gadgets, you could easily rig up something similar for an incubator lacking such an alarm.
When you’re ready to start hatching, set up your incubator and let it warm up for at least half a day to stabilize before you put in any eggs. To keep the temperature steady, locate the incubator away from drafts and where the room temperature remains fairly constant. A room temperature between 75 and 80°F (24 and 27°C) is ideal, although between 55 and 90°F (13 and 32°C) is acceptable.
The better the incubator is insulated, the less it will be affected by fluctuations in room temperature, such as might be caused by sun coming through a window, heat or air conditioning turned off during the night, or heavy storms that cause drastic changes in barometric pressure. Occasional minor fluctuations are normal, so once the incubator’s temperature has been set, don’t keep fiddling with it.
POWER OUTAGES |
The more valuable your hatching eggs, the more you can count on the power going out at a critical time during incubation. After losing too many hatches to extended power outages resulting from spring storms, we got a portable standby generator. If your incubator is electronic, you should also protect it with a surge suppressor. Another option where electricity is iffy or unavailable is an Amish-made kerosene incubator, such as those offered by Lehman’s heritage-hardware store. |
If you don’t have a generator and the power stays off for any length of time, open the incubator and let the eggs cool until the power goes back on. Trying to keep the eggs warm can cause abnormal embryo development. Furthermore, if you close the vents or wrap the incubator with blankets in your attempt to keep eggs warm, a greater danger than temperature loss is oxygen deprivation, and in a prolonged outage the oxygen level could fall below that necessary to keep the embryos alive. |
As soon as the power goes back on, close the incubator and continue normal operation. The effect of the outage on your hatch will depend on how long the eggs had been incubated before the outage and how long the power was out. A power failure of 18 hours will delay the hatch by a few days and significantly reduce the success rate. An outage of up to 12 hours may not significantly affect the hatch — except to delay it somewhat — especially if the outage occurred during early incubation, when cooled embryos naturally go dormant. Embryos that are close to hatching may generate enough heat to carry them through a short-term outage. |
INCUBATOR THERMOMETERS
Wafer Thermostat
The wafer assembly consists of an ether-filled wafer that presses against a switch, and a control bolt to adjust the wafer’s distance from the switch.
Stem Thermometer
A stem thermometer has a probe that goes through a hole in the lid, improving visibility to simplify temperature regulation.
A fully electronic incubator shows the temperature readout in a digital display. Others use a thermometer, which may itself be electronic. Make sure your thermometer is true by checking it against a second or even a third thermometer that you trust for accuracy.
Some thermometers are designed to be placed inside the incubator at the level of the eggs but are so small you can’t easily read them without opening the incubator, which of course causes the temperature to drop before you get a reading. A stem thermometer solves that problem; it has a probe you insert into a hole in the incubator while the readout dial remains on the outside.