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Sponsored by Zoetis

Sponsored By Zoetis


Environmental risk analysis helps ensure best results with in ovo vaccination

Tarsicio Villalobos, DVM
Director, Technical Service, Biodevices
Zoetis Inc.


It’s fair to say that in ovo technology has revolutionized hatchery vaccination of broilers.

Years ago, the only way to help protect chicks against Marek’s disease was by individual, subcutaneous vaccination, which is stressful for the birds as well as time-consuming and labor intensive. Today, poultry companies throughout the world routinely help protect against Marek’s and other diseases with in ovo technology.

In ovo technology also lets producers vaccinate more effectively and efficiently than traditional methods, and improved machine design  makes the process more cost-effective. With the latest Inovoject® M BioDevice, from 12,000 to 20,000 eggs can be vaccinated per hour with only two or three workers.[i]

To get the best results with in ovo technology, however, it’s imperative to make sure the hatchery environment is hygienic. It’s widely known that poor hatchery hygiene can compromise the quality of day-old chicks and, in turn, lead to poor performance later in life. Hatchery hygiene takes on even greater importance when in ovo vaccination is utilized because if there are pathogens in the environment, they could be injected directly into eggs and embryos.

This problem can be avoided if a risk analysis is performed before in ovo technology is implemented. For example, when we perform the analysis for customers, we check for general cleanliness and do a microbial-site survey of the hatchery where in ovo technology will be employed. The analysis helps identify problem areas in the hatchery environment that might adversely affect the in ovo injection process. It also helps pinpoint corrective measures that should be taken before starting in ovo egg injection. The risk analysis can either be repeated once or twice yearly as a general precaution or conducted if a hatchery develops problems that may be related to environmental contamination.


The microbial-site survey conducted as part of the risk analysis includes sampling the hatcher machines and hatcher baskets, the hatcher ventilation system, the general ventilation system, incubator hallways, the setter and setter hallway ventilation, and miscellaneous areas such as the egg room, vaccine preparation room and chick room (Figures 1, 2). The procedure employs 10-minute air plates, swabs to test surfaces, egg touch cultures and, sometimes, down and fluff sampling. We then send the samples to a Zoetis or other authorized laboratory for screening.

Egg Room Air Plates 349x255

Figure 1. Air plates set in the egg room

Ventilation Swab 349x250

Figure 2. Swab-sampling the hatcher intake vent

The labs mainly test for fungi and other potential pathogens. Generally, high fungi levels indicate a problem with the sanitation, maintenance and/or the design of the hatchery’s ventilation systems. Of particular concern are high levels of Aspergillus spp. — specifically, more than 10 colonies on any plate — which can cause mycotic infections in the young chick. Consider that Aspergillus has been identified in about 55% of hatchery room and incubators globally.[ii]

Sometimes these tests help isolate pathogenic bacteria, which can lead to major hatchability depression and increased first-week mortality if they are accidentally injected into the egg. Worrisome bacterial pathogens include Proteus mirabilis, Streptococcus spp., Staphylococcus aureus, Escherichia coli, Pseudomonas spp. and Salmonella spp.

Field example

The results of the microbial analysis can be extremely helpful. As an example, I’ll cite a specific case with a producer using in ovo injection technology.[iii] During the first week of age, chicks showed an increased incidence of general infections, with mortality averaging 3% instead of a more acceptable maximum of 1% or less.

Upon inspection and analysis, my colleagues and I discovered very dirty air moving from the waste-processing area to the washing room and clean storage room. In turn, dirty air was moving to hatchery rooms, and the clean hatchery baskets were becoming contaminated even though they looked clean.

We suggested relocating fans over the waste-processing area to push away all the aerosols and debris released in the air and keeping doors closed in the washing and clean storage areas. After our recommendations were implemented, the problem with infections and mortality subsided.

When risk analysis turns up a problem, the fix is often simple if the hatchery already has an environmental-control system in place. It may be a simple matter of keeping doors closed, which was part of the solution in the example cited above, or replacing a door gasket or executing a better operating procedure.

Hatcheries with no environmental-control system or those using old equipment may require a major investment in updating cooling systems, variable-speed fans, pressure sensors or control software panels.

Of course, in addition to keeping the hatchery environment free of potentially harmful pathogens, it should be obvious that great care must be taken to ensure that vaccines used in ovo are prepared and administered properly by carefully trained staff.

In ovo vaccine advantages

When properly conducted in a hygienic environment, in ovo vaccination can yield several advantages.

At 18 to 19 days of incubation — the time when in ovo vaccines are administered — some but not all maternal antibodies in the yolk have been absorbed by the embryo. This is because full, maternally derived immunity does not develop until a few days post-hatch. If a live vaccine is given to the embryo during this “window,” then the vaccine virus can replicate without too much interference from maternal antibodies. The result is a good immune response at the same time the embryo has enough maternally derived immunity to help protect it from developing disease as a result of vaccination.

There is also evidence that immune priming of late-stage chick embryos produces more immunocompetent chicks at hatch that are better able to cope with infection.[iv]

Studies have also demonstrated that compared to conventional vaccination in ovo vaccination can yield better bodyweight as well as better hatchability, feed conversion and lower mortality.[v],[vi],[vii],[viii]

It’s clear from mounting research and field experience that when properly executed in a hygienic environment, optimal results can be achieved with in ovo vaccination, which in turn can help improve chick performance.



[i] EMBREX. Thinking of in ovo? http://www.embrexbiodevices.com/Thinking-of-in-ovo.aspx

Accessed June 10, 2015.

[ii] Ibid.

[iii] Personal communication with Tarsicio Villalobos, Zoetis Inc.

[iv] Gimeno IM, Cortes AL, Faiz NM, Villalobos T, Barbosa T, Pandiri AR. Role of in ovo vaccination with HVT on the maturation of the chicken immune system. AAAP, Chicago. 2013.

[v] Gildersleeve R, et al. Developmental Performance of an Egg Injection Machine for Administration of Marek’s Disease Vaccine. J Appl Poult Res. 1993;2:337-346.

[vi] Williams CJ, et al. Field testing of the application of Marek’s disease vaccination (HVT) to broiler chickens in Costa Rica – in ovo versus subcutaneous. Sixth International Symposium on Marek’s disease. Montreal, Canada. 2000.

[vii] Bruzual J. Field evaluation of in ovo versus subcutaneous application of Marek’s and Infectious Bursal Disease Vaccines. 54th Western Poultry Disease Conference, Vancouver, Canada. 2005.

[viii] Data on file, Study Report No. 07-13-70AQO, Zoetis Inc.










Posted on August 31, 2015

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