In ovo vaccination has widely been accepted as an effective means of obtaining early immunity in day-old chicks. Particularly in the US the majority of professional large scale hatcheries have adopted this technology. Outside the US, in ovo is also finding its way into smaller sized hatcheries. Basic requirements in the hatchery are essential to let this technology be effective however.
By Dr Tarsicio Villalobos , Director of Technical Support, Pfizer Animal Health Global Poultry, Durham, NC USA
Twenty five years ago the only way to vaccinate broilers against Marek’s Disease (MD) was to give day-of-hatch chicks a subcutaneous injection by hand. It was labour-intensive, stressful for the chicks and delayed their transfer into the growing environment.
On average, one person can inject about 2,000 chicks per hour, so a hatchery producing 250,000 chicks per day needed a team of at least 12 people, and enough room for them to work in. The solution to this bottleneck in the system was the introduction of the first commercial in ovo vaccination device in 1992 by Embrex (now part of Pfizer Animal Health Global Poultry). This new technology not only revolutionised hatchery vaccination but also had a fundamental impact on the way hatcheries operate.
The poultry industry was growing and hatch per day figures were increasing, so vaccination crews were no longer a practical solution. Many people believe that it was the introduction of in ovo vaccination technology which led to the general automation of hatcheries and to many other changes, such as an improvement in hygiene and the use of early vaccination against other diseases.
The USA was the birthplace of in ovo technology and has remained its most enthusiastic supporter ever since. The technology fits perfectly with the business profile of large integrated companies which dominate the market there. Over 90% of all US hatcheries now use in ovo devices, and more than 15 billion eggs are vaccinated globally every year.
The stimulus for the development of commercial in ovo vaccination devices came originally from research conducted by the USDA in the Avian Disease and Oncology Laboratory in East Lansing, Michigan. It showed that embryos could be vaccinated and generate a protective immune response against MD if they were injected just before hatch, between day 18 and 19. The finding triggered the Embrex company to develop an automated device that could deliver a vaccine into the eggs, quickly, accurately and safely for the embryo.
Trigger immune response
One of the key requirements of in ovo vaccination is the ability to deliver the same amount of vaccine consistently to the right site within the egg, every single time. The vaccine must go into the amniotic fluid or subcutaneously into the embryo, if it is to trigger the best immune response. Vaccine delivered into the amniotic fluid at day 18/19 is quickly distributed to the upper respiratory tract, gut and bursa – all key sites for the development of immunity against diseases.
But how do you deliver a dose of vaccine to a tray with up to 165 eggs, in the correct site and all at the same time? Eggs are different shapes and sizes, so the injection locator needs to be able to adjust both laterally and vertically to ensure that the shell of each one is punctured in the correct site. Embrex solved the problem by designing a system of floating tooling heads with an expandable tubing matrix which, for a fraction of a second, receives a burst of air to fix each individual tooling in the correct position and ensure the right needle trajectory on its egg. So each egg is taken care of individually.
Along with the benefits of a more automated hatchery, the introduction of in ovo devices also heralded a more effective way of delivering vaccines to broilers. At 18/19 days, some but not all of the maternal antibodies in the yolk have been absorbed by the embryo; full maternally-derived immunity does not develop until few days post-hatch.
If a live vaccine is given to the embryo during this ‘window’, then the virus can replicate without too much interference from maternal antibodies and thus trigger a good immune response; at the same time the embryo has enough maternally-derived immunity to protect it from developing disease as a result of being vaccinated. The result is a chick which has the earliest possible immune response and thus protection against disease when it moves into the growing environment.
Along the East coast of the US, where a very virulent form of MD virus circulates, chicks are subject to a very early disease challenge. By injecting in ovo, the vaccine has been replicating for 2-3 days before hatch, so when the chicks move to the farm, they are able to cope better with the disease challenge than if they were vaccinated at day of hatch.
Comparable test results
The same applies to Gumboro vaccine, especially where variant Gumboro virus is present, as it tends to infect chicks at a very early age. However, although the potential benefits of earlier vaccination may be obvious on paper, they are not so easy to demonstrate in practice. It is actually quite difficult to show the benefits to an individual producer, because to do that you have to conduct a “pair type” study where all the possible sources of variation are equalised between the in ovo vaccinated and the conventional vaccinated groups.
Such a trial requires that eggs come from the same broiler breeders’ flocks, be stored in the same room for the same amount of time and incubated in exactly identical ways – even down to the proportion of eggs allocated on different levels within the incubator. At the transfer time, eggs have to be separated into two different hatchers to avoid mixing them up when the chicks hatch.
Birds then need to be raised in identical conditions, in two separated houses that share the same ventilation, feeder and drinking systems, with exactly the same initial stocking density. You need to make sure everything is identical, except the vaccination system, and not many producers are willing to do that.
Pfizer Animal Health Global Poultry has data from three such studies however, conducted in 1993, 2000 and 2005 (Table 1
). They generally show improvements in the percent of hatch, mortality, body weight and feed conversion with in ovo vaccination. As might be expected, the exact figures vary between the three different studies. The feed conversion is between one and two points better with in ovo vaccination. In the US, a one point saving represents about $100,000 for a unit processing 50 million birds a year.
Although in ovo vaccination has potential benefits for many hatcheries, it is not suitable for every facility. There are a number of key questions which hatchery managers need to answer in order to determine if in ovo is the right solution for them. Is an approved in ovo vaccine available to match the local disease challenge? Not all in ovo vaccines are available in all countries. Off-label delivery of other vaccines could cause serious problems. In the US the number of in ovo vaccines available to producers has more than doubled, from four to nine, over the last 10 years or so and more are in the pipeline. As the use of in ovo devices increases in other markets, the number of vaccines is likely to follow suit.
How many eggs are processed each month and how many times a week are they transferred out? To justify the use of a full-size Embrex Inovoject, hatcheries need to be processing on average more than 2 million eggs/month. The recent addition of a smaller, semi-automated model to the Embrex product portfolio (model Inovoject m), means that many hatcheries with smaller throughput (<2 million eggs/month) or less floor space can also now adopt in ovo technology. Hatcheries that require processing between 12,000 and 20,000 eggs per hour might consider the smaller machine.
How many different flat configurations are used in the hatchery? Each Inovoject machine is tailor made specifically to work with a particular setter tray. A wide range of different configurations are available, but if the hatchery uses several different flats, it may not be able to vaccinate 100% of all birds in ovo.
If these initial questions produce positive answers, then the next step is to check that the hatchery infrastructure is suitable. To determine this, Pfizer Global Poultry conducts two surveys.
A site survey is conducted to make sure that the buildings, space distribution, storage facilities, utilities (water/electricity), ventilation, air compressor capability, etc are suitable for installing and operating an in ovo device. An environmental assessment is conducted to check the level of contamination. Samples are taken from around the hatchery and analysed for the prevalence of fungi and bacteria, but specially for Aspergillus molds. Because in ovo vaccination requires the egg shell to be punctured, hatchery hygiene is a prime consideration. The need for low contamination risk with in ovo has been a driving force behind the improved hatchery hygiene that has been seen in US hatcheries in recent years.
The survey results determine what work, if any, needs to be done before an in ovo device can be installed and operated successfully. Once all the installation criteria have been met, it is essential that staff are properly trained and onsite support provided.
Pfizer Global Poultry staff stay with the hatchery for the first two weeks, making sure the operators are fully trained and that the device is working properly and optimally. In addition, they leave a stock of common spare parts in the hatchery, so if something happens, parts can be replaced and the device can be working again with minimal down time. Pfizer also operates a rapid call-out support system, and makes regular, scheduled maintenance visits, at least once every nine weeks, to all of its devices in the field.
Making the most of in ovo
Some advice for those hatchery managers who already have an in ovo vaccination device in operation is useful.
At first, one needs to be sure that the vaccine preparation is aseptic. If vaccine is not well mixed and aseptically prepared, then you can jeopardise its efficacy and even potentially kill birds. Each Embrex Inovoject device incorporates a dual needle system to reduce contamination from the egg surface: the outer needle punches a hole in the egg shell and the inner needle penetrates in to the hole to the correct depth to deliver the vaccine. The system is automatically sanitised between injections by having a disinfectant solution washed between the two needles.
Auto-sanitisation is critical to the success of the device because we know that every surface will have a certain amount of bacteria and fungi. However, it is important to make sure the hatchery is clean and sources of contamination such as the ventilation system are addressed.
Initial adoption of in ovo vaccination was highest in those markets where MD is an issue and in those markets that have a more consolidated industry and higher labour costs. It accounts for over 90% of production in the US and the majority of production in Brazil and Argentina. The development and launch of new in ovo vaccines, higher labour costs, and the need to adopt more efficient hatchery technology by an increasingly consolidated industry, means that in ovo vaccination is likely to expand into many other regions around the world.