An eclectic alphabet of chicken facts with a difference, by Andy Cawthray
If eggs are exposed to temperatures in excess of 39.5C in forced air incubators (or 41.5C in still air incubators) for just a few hours it is lethal for the embryo inside. On the flip side, if there is a power cut, or a broody leaves a nest for a long period of time, embryonic development slows down but doesn’t result in the death of the embryo unless the time period exceeds 15 hours. The eggs will have chilled, but the metabolism of the embryo will only have slowed down, and will recover once the temperature increases. Such breaks in incubation will delay the hatch and may result in slightly reduced success, but it will not necessarily result in embryonic death.
During incubation, eggs require turning. Turning the eggs will dramatically improve the hatch rate of those which are fertile. The reasons for turning are to prevent the embryo from sticking to the
side of the shell. This will stop the chick from being able to move into the hatching position when the eggs have reached term. Turning also ensures an even temperature is achieved within the egg. It also improves and refreshes the contact between the embryonic membrane and the nutrient rich albumen within the egg. There is no need to turn eggs placed under a broody hen as they naturally turn their eggs through shuffling on the nest and general movement
The eggs should be positioned in the incubator so that the blunt end is higher than the pointy end as this is where the air sac is located. Eggs should also be stood blunt end up and turned during storage.
SINGLE CHICK SYNDROME
If too few eggs are set or, upon candling, too few are found to be fertile, there is a risk that only a single chick will hatch. If a broody is being used this doesn’t present too much of a problem. If, however, an incubator is being used the resulting single chick will still require the same levels of brooding heat post-hatch as a clutch would, plus it will become quite vocal as it tries to get a response and find fellow chicks.
Unless there is a ready supply of day old chicks that can be added to the single bird to enable flock interaction, correct imprinting and development, then it would be worth considering stopping the incubation early if the risk of a single chick hatching is high.
The ‘egg tooth’ is a small, sharp temporary cap that sits on the end of the beak of a chick. It develops whilst the chick is within the egg and has two key uses. The first is to help the chick break into the air sac within the egg. It is then the more commonly known function of the ‘tooth’ comes into play, which is when the chick uses it to break out of the shell; this is known as pipping.
Not all fertile eggs will hatch. Some may show good development on candling, but embryos can die at any point prior to reaching term. This is usually referred to as ‘death in shell’ and establishing the point of development at which the chick died can help in diagnosing the possible cause. There are, however, many factors at play, and isolating any particular single, or group, of factors responsible can be difficult. It is worth keeping hatching records as these will help identify any patterns that might emerge. It is also worth noting the timings of the hatches. Under normal circumstances chicken eggs will take 21 days to hatch. Any significant differences can be attributed as follows: Eggs hatched early – small eggs, high temp, low humidity, young breeder stock; Eggs hatched late – large eggs, low temp, high humidity, old breeder stock.
Not all deformities that occur in chicks can, or should, be put down to genetics (although a number can be). The manner in which eggs are kept prior to setting can also be a root cause.
Deformities such as crooked toes and splayed legs can often be attributed to poor egg storage.
Once the chicks are full feathered (usually around 6-7 weeks) they should no longer require heat and (subject to the weather) be quite capable of living outdoors full time. Prior to that, there is no reason why chicks can’t take ‘day trips’ outdoors on fine days and be returned indoors to shelter and heat overnight. This will help them develop and grow faster – though bear in mind that very young chicks can soon chill, so only let them outdoors on warm days and when someone is present to bring them indoors should the weather change for the worse.
INTRODUCTIONS TO EXISTING FLOCK
Introductions can get a bit messy if the pecking order within the existing flock is well established and dominated by one top hen. The best thing to do is to put the new birds in to the coop after dark when the residents have already gone to roost. This not only helps the new birds understand where home is, but also gives the residents a chance to interact with the new birds come first light. In many cases this can be enough for the birds to be accepted, but the following day there will be some initial squabbling as the pecking order is reset. If persistent bullying occurs then look to remove the bully (and not the bullied) for a few days until the pecking order has settled. Understanding the behaviour and flock dynamics will also help in identifying issues and ascertaining the right course of action.
ABOVE: Antique still-air incubator
ABOVE: Cradle eggs ABOVE RIGHT: Chicks outdoors BELOW: Hatching problems FAR RIGHT: A single chick