Breakout analysis on day 18 The primary goal of transfer-candling is to only transfer viable embryos to the hatcher baskets. Carry out a breakout analysis on eggs selected out at the time of candling. Candling and breakout analysis can signal problems in the incubator. For example, you can identify locations in the incubator where embryo development is retarded. But you cannot easily distinguish eggs with early mortalities because they have already been deteriorating for 18 days. Depending on the findings, you could candle on various days, to pinpoint potential problems. Only examining eggs rejected at transfer gives you a limited picture. To obtain a fuller picture, you should also assess unhatched eggs (from the same setter trays). This is, after all, the actual mortality after day 18.
Caution! Don’t take immediate action based on the results of one breakout. Check eggs from the same flock again using another setter. Or check the setter again with eggs from a different flock.
Use standard forms
te
d
Always assess the breakout in the same way. Use a standard form, on which you put all important information. You can subsequently enter this in a computer and analyse it. So don’t put all the information on paper in a file cabinet!
1-2 days: germinal disc
3 days: blood ring stage
A clear, white point, sometimes slightly grainy. Causes: poor quality males or females, or an incorrect ratio, seasonal and/ age-related decline in parent stock fertility, competition among males, diseased flock, or parasites, e.g., mites. Insufficient floor space (= stress).
Enlarged embryonic disc, with no blood, a round embryo, and a light-coloured yolk. Causes: undernourished males or too many of them (= stress for the females), damaged eggs, cooling too fast or slow after laying, and prolonged/incorrect storage. Very young or old parent stock. Excessive washing water temperatures. Difficult to identify at 18 days.
A clear egg with a blood ring or one with whitish-yellow content is a typical image of mortality after three days of incubation. There is still no black eye visible. Causes: excessively long or incorrect storage (temperature fluctuations), incorrect disinfection, incubation temperature too high or low, damaged eggs, old parent stock, and poor nutrition.
4-10 days: black eye stage
11-18 days: feather stage
Rotting egg
Start of the yolk sac with blood vessels. The embryo is lying on its right side, still no egg tooth, but the eye is very clearly visible. This can have the same causes as early embryo mortality before day 3. Or be caused by insufficient ventilation, impenetrable eggshell, CO2 concentration higher than 1%, insufficient turning frequency, incorrect turning angle, or a vitamin deficiency.
You can recognise an embryo that died after day 11 by the presence of plumage.
You see a grey-green mass in the egg. There is an odour of rotten eggs (hydrogen sulphide, and ammonia). The causes include lack of hygiene in the laying nest, setting floor eggs, incorrect storage conditions, moisture on the eggs.
co
py
rig
ht
pr ot
ec
Day 0: infertile
8. Tr a n sf e r
129
