Thursday, 2 April 2015

Goose egg hatching guide

The goose egg season has started and the first eggs are in the incubator, so I'm going to write down the techniques I've had most success with when incubating and hatching goose eggs in previous years.

The first time I tried to hatch goose eggs, this happened:


Two of the eggs hatched but the goslings were sickly and later died (we never did get to the bottom of what had caused this; a necropsy on one of them found severe neurological damage due to vitamin E deficiency). The remaining eggs when opened mostly contained fully-developed goslings that were waterlogged and had died before internally pipping. This was because the eggs did not lose enough moisture during the incubation, and the goslings had too much fluid inside the shell and did not have a large enough air space in the egg to be able to pip into. There is unfortunately not a lot of good information on the Internet or even from other people with experience breeding birds about how to hatch goose eggs, and one piece of misinformation that seems to be particularly pervasive is that goose eggs need high humidity throughout incubation. The reasoning often given for this is that geese are water birds, and a goose sitting on a nest leaves the nest and goes in water, and when she returns her feathers are soaked and make the eggs wet. There are two main problems with this reasoning:

First of all, it is an appeal to nature fallacy. Supposing geese even did sit on sodden nests in the wild, this does not necessarily mean these are optimum conditions that we should try to replicate in artificial incubation techniques.

Secondly, you may be familiar with the phrase 'water off a duck's back'. The plumage of ducks and geese repels water because the birds preen themselves with an oil from the uropygial gland. Water does not stick to a duck's back, and neither does it stick to a goose's front.

Clearly, doing something a particular way just because it seems to be most similar to something that is perceived to happen in nature is not a good strategy if we want the best results. We should strive to do things in the way that is most likely to result in success, and that sometimes means trying different methods and comparing the results in order to discover what works best. Using the method I have found to work best, last year I achieved on average a 75% hatch rate on eggs I acquired through the post. I hope that I will continue to improve it and get even better results as time goes on.
The first thing to understand is that goose eggs need to achieve a mass loss down to 84% of their starting weight by the time they are ready to hatch. This mass loss occurs through evaporation through the shell. You ideally should monitor the weight of your eggs to check they are on track. You can do this by plotting a graph like so:


You can then weigh your eggs on any given day and divide the current weight by the starting weight, multiply by 100, and see if your egg is close to the line where it is supposed to be.

The eggs spend the incubation period (the first three weeks) in a forced air incubator, a Brinsea Octagon in this case. Do not put water into the water trays at the bottom. If you really must put something into the trays, put silica desiccant in (I'm not joking). Silica desiccant can be ordered online and it comes as small beads that change colour when they absorb moisture, which are a right horror if you spill them anywhere. You need to buy the orange ones that turn green, not the blue ones that turn pink. The blue ones contain cobalt chloride which is not good for your health and probably won't do the eggs much good either.

Another way you can monitor the moisture loss from the eggs is by candling and drawing a line where the air cell is. Halfway through incubation, the air cell should look something like this:
 

After the internal pip, just prior to hatching, it looks like this (part of the change in size is due to the embryo changing position, so the air space gets significantly bigger in just a few days):



What you can do if you are concerned that some or all of your eggs are not losing enough moisture. I have heard some diehard humidity fanatics claim that spraying goose eggs with water every day helps to increase evaporation. I have no idea if there is any truth behind this, but personally I would not want eggs in an incubator getting wet every day. Eggs are not sterile and it increases the risk of bacteria and fungal organisms growing on them and in the incubator. What you can do is make a hole (or three) in the air space end of the egg to increase evaporation. Use the candler to make sure you are only penetrating the air space, and use a small drill bit manually or the point of sharp embroidery-type scissors to make the hole, taking care not to push the tool beyond the other side of the shell.


Above is an example, in a tray of silica gel inside the hatcher.

A week before the eggs are due to hatch, you can transfer them from the incubator to a still air hatcher and stop turning them. You do not need to increase the humidity in the hatcher until the eggs start to pip externally, and you might find some of the eggs still have not lost enough weight, in which case you can put the worst affected eggs into silica gel trays to help try to get the weight down before they start hatching.

Once the hatching begins and the first cracks on the shells are seen, it is very important that all the silica is removed and the humidity in the hatcher is increased as much as possible. Goose eggs take a long time to hatch, and the high humidity prevents them from drying out and getting stuck in the eggs. The still air hatcher I have always found to be much better at maintaining a good hatch humidity than the forced air, where the fan tends to dry out the membranes no matter how much water and wet cloths are added. At this point you can spray the eggs from time to time with tepid water, since the goslings are now ready to come out into the world in all its filthiness and any bacteria on the shell is unlikely to do any harm to them now.

Sometimes goslings do need intervention to help them hatch, and having bigger eggs and a larger volume of blood they are much more tolerant to human interference than things like chickens. In my experience, I have never been able to save a bird that is unable to pip internally by itself, although when a bird is malpositioned and cannot pip by itself, there is nothing to lose and no harm trying. With goslings that have internally pipped and seem to be having trouble with the external pip, the shell surrounding the air space can be dismantled with the aid of a candler and the membrane checked for active blood vessels. If any bleeding occurs, stop and wrap the exposed parts of the egg in wet kitchen paper (leaving sufficient room for the gosling to breathe) and return it to the hatcher.

Hopefully, if all goes to plan, you should get some of these. :-)



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