How can I tell if an egg is fertile?
When a bird is laying eggs, and a few days prior, she is receptive to mating. The male indicates his interest by courting behavior. If the female is receptive, she will crouch. The male steps on her back, squats down so that the vents can touch, and releases the semen. Sperm cells must then migrate the whole length of the female reproductive tract to join with the egg cell that is on the yolk. Fertilization must occur in the infundibulum. As a result, the blastodisc on the yolk becomes a blastoderm. During the 24 or more hours that the egg is being formed by the hen, the embryo completes several series of cell division. Instead of the one cell present at fertilization, the developing embryo has aproximately 256 cells when the egg is laid.
The photo shows the difference between
the blastodisc of an infertile egg and the
blastoderm of a fertile egg. After the egg
cools to room temperature, development
of the embryo stops.
Sometimes in extra dark Marans eggs the
slow transit through the oviduct means
that the developing embryo will be too far
advanced to stand the shock of being layed
temperature change being too great for
the embryo. This will appear to be an infertile
egg, but it is actually an early death
If the rooster in a flock dies, or is removed, the hens will continue to produce fertile eggs for up to four weeks. This is because there are "sperm nest" areas located in the oviduct of hens that collect and store semen for later fertilization of eggs. This is a natural survival mechanism for the production of a series of fertile hatching eggs even after the male is not available.
The period of time that fertile eggs can be produced without additional matings can extend to several weeks. If a rooster is removed from the flock and replaced by another, it may require 3 weeks before it can be assured that all eggs will produce chicks sired by the new rooster. The proportion of chicks sired by the new rooster will increase during this period, but some chicks sired by the old rooster may hatch. Birds like turkeys and waterfowl have longer periods during which fertile eggs can be produced without matings.
Conversely, if a female is averse to being mated by a particular male, but by bullying or persistence he forces her to mate it has recently been found that the female can choose to eject the sperm. To counteract this inferior males will produce larger quantities of ejaculate to give them a better chance of reproducing.
The following notes were written by a Commercial Hatching Egg Producer in New Zealand:-
Having been involved with producing hatching eggs on a commercial scale for many years and have had experience in packaging eggs for transport, from 6 eggs to many thousand per consignment and from sending them 2kms down the road to all over NZ, including on the ferry and by air, road and car and also to the Pacific islands and also receiving hatching eggs from USA, Canada and UK.
Here are some observations that may help clarify a few points
No breeder of poultry should claim 100% fertile eggs and expect them to hatch at100% Even if they are 100% fertile, they may well not all hatch due to a variety of circumstances. eg the dead in shell are fertile, just dead!
Eggs do not need to be laid on the same day to hatch on the same day. They can be stored over a period of time, possibly up to 3 weeks. The 21 day hatching period commences when the eggs all reach incubation temperature i.e. over 26C together. Eggs that are less than 24 hours old when incubation commences will not hatch as well as those that are 24hrs old or older and have been allowed to cool down from 40c at laying to about 16c in 4 hours and stored at that temperature for more than 20 hours.
Eggs up to 10 days from laying, provided they have been stored at between 16c and 18c, will hatch equally well. After 10 days old, hatchability will reduce by approximately 1% for each day older than 10 days. Eggs that are more than 3 weeks old at the start of incubation probably have a 50% hatch probability if they were likely to hatch at 80% when they were only a couple of days old.
Storage and transport may have a huge effect on the hatchability, even if they had been fertile in the first place. Eggs which have been stored will take longer to hatch. Low incubation temps will cause eggs to hatch late and eggs from old breeders, just as high incubation temps and eggs from young breeders,will be quicker to hatch. That is more than 21 days for old eggs and 19 to 20 days for early.
Thousands of hatching eggs travel regularly between North and South Islands on the plastic trays they are to be incubated in, packed straight from the nests on to the flimsy plastic, skeleton type trays holding 36,42 or up to 180 eggs each. Stacked into wire cages, wrapped in cardboard (to prevent theft!)at +4000 eggs per pallet, loaded by forklift and transported by road. Very few get broken or cracked in transit and despite being up to 10 days old they will still hatch in the mid 80%
Eggs going overseas are packed direct on to grey fibre 30 egg trays, 6 trays to a carboard box, upturned tray on the top layer, a wedge of newspaper, lid folded down and taped. Boxes loaded on a pallet, 6,780 eggs to a pallet shrink wrapped, than several pallets per shipment. They arrive in Noumea, or Vanawatu or Fiji or Papua New Guinea or wherever, and we still expect them to hatch as they would have done at home.
Accidents do happen, eggs get left at some remote tropical airport in the sun, or some kind person puts them in the chiller, or a forklift goes through the boxes somewhere. We even had a truck fall off the road somewhere in the depths of the King Country, but they usually mostly hatch, given the chance! After the transport process the incubation of them can be just as much to blame on getting a poor hatch. 12 eggs is too much for some hens to warm equally so eggs on the periphery may be slow or even die mid incubation. Internal bacterial contamination can also be to blame.
By the way, felt pen marks on eggs do not affect hatching. Every tray of eggs produced in a commercial breeding operation has several eggs marked with flock number, date, a farm and shed- they hatch just as well as the unmarked ones.