Size and uniformity

from Hatchery Signals - English edition

Navel and cloaca

Size and uniformity

The hatching eggs must be as uniform as possible to ensure the eggs are incubated as uniformly as possible and to avoid large variations in the weight of the day-old chicks. Each type of egg has its own specific incubation conditions, which can even differ according to the breed. The incubation conditions must therefore be adapted according to the type of egg/the quality (and take into account the type of incubator). Embryos in large hatching eggs will produce more heat and have more difficulties dissipating heat, and therefore need more cooling. Embryos in small hatching eggs will produce less heat and need less cooling. The optimal temperature for embryonic development is identical for all embryos. It is 37.8 C whether the eggs are small or large. If the hatchery manager is not satisfied with the uniformity of the hatching eggs, he/she should inform the breeder farmer. In this case, there is usually something wrong with the uniformity (weight) of the parent flock. Eggs laid by very young flocks are often less uniform, and uniformity also often declines as the parent flock ages!

Screening based on size. If the size of the hatching eggs is not uniform, the spread in the hatch window will very wide. This can be reduced by grading based on weight and by sufficient pre-warming, the so-called ‘pre-warming phase’ (= 5-6 hours pre-warming at 25 or 27°C before the incubation program starts). Egg weight is a good predictor of the day-old chick weight. The chick weight at hatch can be calculated based on 2/3rds of the egg weight. An egg of 60 grams will hatch on average a day-old chick weighing 40 grams. However, chick weight is NOT a measure of day-old chick quality. The amount of remaining yolk is copyright protected an indication (or the chick’s body weight without residual yolk, i.e., the yolk-free body weight or YFBW). Large and small eggs being separated during selection at the breeding farm.