It’s what’s inside that counts

The process of vaccinating chicks before they have even hatched is growing in popularity, with producers reporting better immune responses, fewer secondary infections and lower numbers of missed birds.

“In-ovo” vaccination was invented in the early 1980s and can be used to vaccinate against diseases such as Mareks disease, Gumboro, Newcastle disease, Avian Rhinotracheitis and infectious laryngotracheitis, pox and coccidiosis.

As the available vaccines for use in-ovo increases, and poultry farms grow in size, the number of producers using the technique has skyrocketed, with 30% of the world’s broilers, or 15bn eggs per year, now vaccinated in-ovo.

Speaking at the Pfizer Poultry Partnerships Days symposium in Vienna in late November a range of experts from France, the Netherlands, USA, Spain and Germany spoke about the technique, their experiences and its advantages.

Dr Jan-Kees Van Den Wijngaard, poultry veterinarian, consultant and former biological operations director for Pfizer Poultry Heath said in-ovo had significant advantages over manual vaccination, which stressed chicks and provided protection too late or not at all.

“This (manual vaccination) brings a lot of stress to the birds, the birds start to fly away and they are not always unsuccessful in escaping vaccination,” Dr Van Den Wijngaard said.

“In some field surveys you cannot find antibodies after vaccination in 50% of chickens. This is very important if the virus shows up in the field.”

Dr Van Den Wijngaard also said that manual vaccination was impractical on large farms (40,000+ birds) with it almost impossible to be sure birds received an adequate dose of vaccine if administered via spray or in drinking water.

In the USA, in-ovo vaccination is the standard procedure for vaccinating against Maddox disease, while in France 80% of free-range “Label Rouge” chicks are vaccinated in-ovo.

“After 15 years of experience we are totally convinced of this technology. This high-value [process] has a very low mortality and condemnation rate. Vaccination has proven to be very efficient,” said Dr Vet Brice Robineau from Chene Vert, the largest veterinary group in France.

“The weekly production range (in French hatcheries) is between 50,000 and 300,000 chickens and there are presently nine hatcheries vaccinating in-ovo against Marek’s disease.”

Dr Robineau predicted that all vaccination will occur in-ovo at the hatchery level in the future as more vaccinations are developed.

Issues raised by vets at the symposium related to the animal welfare implications of injecting vaccines before birds have hatched and the inability to sex chicks while in-ovo, resulting in females and unwanted male chicks all being treated.

A panel of experts from Pfizer were also questioned on whether they had any evidence relating to the stress the bird undergoes in being vaccinated in-ovo.

Pfizer global technology director Tarsicio Villalobos said they had noticed an increase in the heart rate of the chick, but this didn’t necessarily mean stress on the bird.

“How much is this a stress on the embryo? We don’t know. What are the implications for animal welfare? We don’t think it’s any more stressful than the whole hatching process itself,” he said.

Sexing was raised as currently, using conventional methods, birds are sexed before vaccination and so only the female birds used for production receive treatment whereas with in-ovo all birds are vaccinated.

Dr Van Den Wijngaard said at the moment the problem is logistical with samples needing to be taken from the egg, tested, and then the original egg has to be located and injected or disposed of.

Dr Villalobos said Pfizer was working on a device that would analyse DNA from the egg or chick and return a finding as to its sex as part of the vaccination process but this was still in the research stage.

What is In-ovo vaccination?

In-ovo vaccination is the process by which vaccines are delivered directly into the amniotic fluid within the egg, or within the embryo itself.

The egg is injected with the vaccine between 17 and 19 days of age or within 48-72 hours of hatching – normally when the egg is transferred from from the setters to the hatchers.

Specifically Pfizer recommends injecting the vaccine between 18 and a half and 19 days.

Eggs are pierced by a punch which contains a smaller needle which enters the amniotic fluid inside the shell, which still surrounds the chick, and delivers the vaccine.

When the needle and punch are extracted from the egg small holes at the top of the needle spray a small amount of chlorine solution on the outside and the inside of both the needle and the punch, sterilising the surface and preventing egg-to-egg contamination.

As the chick moves closer to hatching it sucks the remaining amniotic fluid into its body, drawing the vaccine into its system at the same time.