In order to save energy and labor, we can give breeders and broilers limited space during the first days/weeks of their life. This partial brooding is often done by partitioning the house for a limited period, or by placing birds of different houses together for the first weeks, after which the birds are moved to their final rearing house.
Although this is a good practice to use the space and heating systems more economically, we have to realize that it can influence the effectiveness of a coccidiosis vaccination.
To build up immunity against coccidiosis, it is crucial that the birds recycle the vaccine oocysts from the litter. The immune system of the birds needs to be exposed several times to the vaccine oocysts to be able to develop a good immune response.
The first contact is done by the vaccine exposure. As a day old chick or within a few days after placement, the vaccine is given and the immune system of the birds will be activated by the sporulated oocysts in the vacine. As a result of this vaccination and the life cycle of the parasites, immature oocysts are excreted into the litter.
These oocysts have to sporulate in the litter (with the correct temperature and humidity) and have to be ingested again by the birds for a second cycle. Only after a few of these cycles, the birds will be protected against field challenges.
It is therefore important that the birds keep in contact with the faeces in the litter for at least the first 2 weeks, but preferably even longer than that. When we move the birds from one house or one pen to another area with new litter within 2-3 weeks after vaccination, there is a change that the recycling of the vaccine stops and the immunization of the birds will not be maximal.
This for instance also means that when we do partial brooding followed by early grading (grading in week 2-3) in breeders, we need to make sure that the pen for the graded birds has been in the area where the birds were initially placed. If not, the graded birds will be placed on new litter and vaccination might be impaired.
Also placing part of the birds after partial brooding into other houses on the farm should not be done too early, to ensure that there are enough oocysts recycled by the birds to build up sufficient immunity.