Uniform ingestion of coccidiosis vaccines made of attenuated sporulated oocysts is of paramount importance for the correct intake of these vaccines and subsequent onset of immunity and has to take place soon after the vaccine is coarse sprayed over the chicks. In order to achieve this, we need to enhance the pecking and preening behaviour of the chicks with the help of a colour and an aroma.
The application of vaccines via coarse spray was conceived mainly for the oral administration of coccidiosis vaccines made of sporulated oocysts.
This type of vaccination requires a droplet size of more than 200 microns, which is achieved by controlling the type of nozzle and the pressure that are used. For consistent vaccination, active ingestion of the vaccinal water droplets containing oocysts is crucial. It has been reported in the literature that the inclusion of colouring agents has a marked effect on coarse spray vaccination, inducing greater preening activity and thus increasing the ingestion of spray-applied vaccines.
The ingestion of oocysts contained in the vaccinal water after coarse spray administration is achieved by the birds actively pecking the droplets that are located in the feathers of other birds or by pecking the droplets from themselves (behaviour called self-preening). Any component of the vaccinal water that increases the ability of the birds to locate the droplets or enhances the intake of vaccinal water droplets will be of great importance for correct and homogenous vaccination.
The selection of the components to be associated with the oocyst vaccine HIPRACOX® started by studying the work of other authors in which the colour preferences in young chicks had been described. It has been reported that chicks have colour peak preferences in the orange-red and blue-violet regions (Fischer et al.). 1, 2
However, blue-violet seems to be the colour spectrum of maximum preference of one day-old chicks and because of that, this was the colour spectrum selected.
Due to the fact that blue-violet (a secondary colour) can be only achieved by mixing two primary colours, a red colour and a blue colour were chosen, giving a light purple as a result.
By the addition of the light purple coloration to the vaccinal solution containing the oocysts, under normal light conditions the birds easily detected the vaccinal droplets and thus homogeneity of vaccination was improved.
Caldwell et al.3, 4 demonstrated a direct correlation between ingestion of droplets containing oocysts (increased preening activity) and photo-intensity. Unfortunately, the conditions of light intensity in most hatcheries is very poor in the area were chicks are spray vaccinated or in the area where the cages are piled up after vaccination and stored before transportation to the farm.
Commonly, light intensity in working conditions needs to be between 200 and 300 lux. However, the study of several hatcheries showed that where coarse spray oocyst vaccination takes place, light intensities varied from 100 to 200 lux, and was even lower in one (80 lux). Fischer et al.2 demonstrated that birds have light-adapted viewing, thus, these low light intensities could adversely affect vaccination. Moreover, light intensity is also decreased by the fact that after vaccination birds’ boxes are commonly piled up, further decreasing light conditions.
Because of this, the colouring agent was also selected for being the one that gave better results at a light intensity of less than 100 lux. Moreover, another component was introduced to the colouring agent to solve this problem: an aroma.
It is interesting to mention that Burne et al.5 demonstrated that birds can respond to odorants and that they first use the visual stimulus and secondly they can use an odour stimulus. Because of this, the possibility was investigated of introducing an odorant into the final colouring agent in order to make it effective at poor light intensities as well.
We finally decided to include vanillin in the formula due to the fact that it increased the number of pecking events in conditions of poor light intensity (80lux).
In conclusion, the components selected to be included in the colouring agent for administration of the oocyst vaccine HIPRACOX® via coarse spray enhance the ingestion of the spray-applied vaccine in conditions of either normal or poor light intensities.
HIPRACOX® and now also EVALON® are the only coccidiosis oocyst vaccines with a dedicated colouring agent and aroma which are able to enhance the intake of the vaccine even under poor light conditions.
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