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.
1 point: head under wing
pr ot
ec
te
d
Criteria: Position
3 points: external pipping
2 points: internal pipping
co
py
rig
ht
Criteria: Yolk residue absorption
1 point: organs still outside body
2 points: dual-lobe yolk sac
3 points: single-lobe yolk sac
4 points: fully absorbed
Recommended score and injection site per score
1
X
2
X
3
ᅚ
Allantois/Air cell/Yolk sac
8. Tr a n sf e r
4
ᅚ % Amnion
5
ᅚ
6+7 % 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
Percent in site
100 90 80 70 60 50 40 30 20 10 0
121
