The fresh egg breakout has the advantage of being the quickest way to estimate fertility in the breeder flock. It is useful when a flock begins to lay eggs or if a flock has been treated for a disease or fertility problem. Fertility can be determined on the day the eggs are laid rather than (having to wait until after the egg storage time and the incubation time for the opportunity for candling or hatch day breakout…not clear) For example, if there is a storage time of one week and fertility is determined by hatch day breakout analysis, then the information regarding flock fertility is four weeks behind the flock performance. Management changes, in this case will take a long time to incorporate. However, there are numerous disadvantages associated with the fresh egg breakout.
The most serious disadvantage of a fresh egg breakout is that it only provides information on fertility estimates. A company relying on the fresh egg breakout analysis will not gain valuable information on other important sources of reproductive failure such as embryonic mortality, contamination, pips, hatch of fertiles and many others. A second disadvantage is the loss of valuable hatching eggs due to the procedure. However, a relatively small sample size is normally used for fresh egg breakouts. Because valuable hatching eggs must be used, the sample size rarely exceeds 100 eggs, resulting in the third disadvantage errors of prediction. Rarely are samples of fresh eggs large enough to provide an adequate sample size, leading to sampling error. The other two methods of breakout require the evaluation of several hundred eggs, but only problem eggs in a sample are evaluated. A fourth disadvantage of a fresh egg breakout is that it is more difficult to distinguish between fertility and infertility in fresh eggs than when eggs have been incubated for several days. Distinguishing fertiles from infertiles is certainly not impossible after a little practice. To correctly distinguish the differences in fertile and infertile eggs, the egg contents must be poured out and the germinal disc must be found.
There are three criteria that should be used to determine fertility/infertility of a germinal disc; shape, size, and color intensity.
1. Shape: Upon close observation, a blastoderm (indicating fertility) is always round (i.e. almost perfectly
uniform and symmetrical). Hatchery personnel often refer to this shape as a “doughnut.” The doughnut
appearance is seen as a white symmetrical ring with a clear area in the center of the ring (Plate 1). Sometimes
a white dot will be present in the center of the clear area. The blastodisc (indicating infertility) is rarely
perfectly round, and has jagged edges. There are usually more vacuoles (bubbles) present in the periphery of
the blastodisc than the blastoderm (Plate 2).
Plate 1. A fertile egg
Plate 2. An infertile egg
2. Size: The blastoderm is almost always larger in appearance (one- quarter to one-third larger) than the
blastodisc.
3. Color Intensity: The blastoderm almost always appears to be a less intense color of white than the
blastodisc. The blastodisc appears as more of a small, intense white spot on the surface of the yolk.
Sometimes the blastodisc is granulated. Instead of one white spot, there may be several clumped white
spots.
For learning the technique of distinguishing between fertile and infertile germinal discs, it is helpful to make side by side comparisons of eggs known to be fertile and eggs known to be infertile. It may help to place the yolks in clear petri dishes and gently compress the lid down onto the germinal discs. This makes the discs stand out to allow comparisons of shape, size and color features. The beginner should use a magnifying glass to help make these determinations.
During a fresh egg breakout, it is important to have a sample size of at least 100 eggs per flock. Because of the disadvantages involved in the fresh egg breakout, this procedure is not recommended unless a quick fertility check is desired. Candling and/or hatch day breakouts should be done more routinely (every one or two weeks).