The optimal timing

The optimal timing

In-ovo vaccination is done at the time of transfer. The vaccination window is day 17 1/2 until day 19 1/4. But you cannot actually measure this in days, it is determined more by the stage of embryonic development. This is determined by looking at the extent to which the chick is in the position to hatch (head under the right wing) and/or if the yolk is sufficiently retracted. No more than 1-2% of the eggs should show external evidence of pipping. Optimal uniformity is therefore highly important here.

Scoring system

A scoring system has been developed for determining the development stage of embryos. If the sum of the scores on two criteria is 3, it is a good time to vaccinate.

Criteria: Position

1 point: head under wing

2 points: 3 points: internal pipping external pipping

Criteria: Yolk residue absorption

1 point: organs still outside body copyright protected 2 points: 3 points: dual-lobe yolk sac single-lobe yolk sac 4 points: fully absorbed

Recommended score and injection site per score

100

Percent in site 90 80 70 60 50 40 30 20 10 0

1 2 3 4 5 6+7 X X

Allantois/Air cell/Yolk sac % Amnion % Embryo With a higher score, more vaccination fluid penetrates the embryo and less in the amniotic cavity. From score three upwards, the vaccination result is better.

Source: Zoetis