For various reasons, including the continuous reduction in the duration of the growing period of the broiler, the increase in size of poultry operations and the frequent difficulties to find properly trained and/or motivated work force at farm, vaccination at the hatchery is becoming more and more popular and will certainly develop strongly in the coming years. It includes administration of the vaccines either by injection (“in-ovo” or subcutaneous routes) or local application (spray or eye-drop). For many years, this has been the only way to ensure an early and/or improved resistance to mucosal diseases like Infectious Bronchitis or Newcastle Disease.

More recently, new types of vaccines, based on immune complex or recombinant technologies have been launched. Both have proven to be capable of inducing active immunity in the presence of Maternally Derived Antibodies (MDA), which were previously neutralising classical live attenuated vaccines if given at a too early age. This capacity, associated with the precision and the reliability of individual injection, is responsible for much better vaccine coverage of the flocks. Vaccination at the hatchery is actually opening the door to a real control of broiler diseases.

Protecting genetic potential

One of the current key challenges of the poultry meat industry is the control of broiler health. This is not only to avoid disease outbreaks, but more importantly, to protect the full expression of the genetic potential. Protection weighs heavily on the economy of the production and limits contamination by zoonotic pathogens, which could significantly decrease the commercial value of the final product. The backbone of any sound policy aiming at controlling broiler health and reducing the risk of disease is biosecurity, and no real and long lasting success can be expected in this area without real and solid implementation of it at both breeder and broiler levels, including the hatchery.

Vaccination is a complementary approach to biosecurity and there is nowhere today where we can actually think of not doing it. However, major changes are occurring in this field aiming at making vaccinations easier to apply, less expensive and more efficacious. This is why vaccination at the hatchery has recently gained such popularity and is developing quite fast within the poultry industry.

Main problems associated

Immune complex Gumboro vaccines have the capacity to delay the release, and hence the replication of the vaccine virus up to an age where the maternally derived antibody level has reached a point that is no longer capable to neutralise it.

For many years, considering quality, reliability and cost effectiveness, vaccination at the hatchery had been regarded as the optimum situation for vaccine application by people involved in poultry production. However, until recently, only a few vaccines could honestly be recommended to be given at the hatchery with consistent (Marek’s disease (MD), Infectious Bronchitis (IB), Coccidiosis) or acceptable (Newcastle Disease (ND), Swollen Head Syndrome (SHS)) efficacy. The main reasons why vaccination against other diseases like Infectious Bursal (IBD)/Gumboro Disease, Laryngotracheitis (ILT) or ND was not possible were:

• The lack of adapted or reliable equipments

• The problem of interference between MDA and live attenuated vaccines

• The residual pathogenicity of some vaccine virus.

Development of new equipment

One of the main requests for vaccination to be given at the hatchery is the possibility to make it automatic and fast, with a low percentage of not or badly vaccinated chicks and a reduction in costs associated with vaccine application. Many developments have recently been made in this area and today, powerful and user-friendly equipments are available to poultry producers for vaccination by eye-drop, coarse spray and fine spray, subcutaneous injection at day old and “in-ovo” injection at 18–19 days of embryonic life.

Some of this equipment also allows association of two or more vaccinations (spray and injection, double injection) at the same time. However, although reliability has improved and sophistication added, this should not be regarded as a perfect solution and an eye should always be kept on them as well as on the operator, and the quality of vaccine application regularly checked. Various devices and procedures have been developed for this purpose.

Breakthrough of new vaccines

Many new vaccines have recently been introduced in the market, and more are still to come. Because of them, the range of vaccines applicable at the hatch has enlarged and the cost benefit ratio of expensive equipment like “in-ovo” injectors strongly modified in favour of hatchery vaccination.

Among these new products, the following are worth a mention:

• Live attenuated ND vaccines of the “enterotropic” type: These viruses are naturally apathogenic for the chickens and can induce local immunity without creating lesions of the trachea as classical “tracheotropic” live ND vaccines do, leaving chickens more susceptible to secondary viral or bacterial infections. With this new category of vaccines, no rolling infection is observed, growth is improved and consumption of antibiotics is reduced. This category of apathogenic live attenuated ND vaccines has really contributed to the spreading of ND vaccination at the hatchery.

• Immune complex IBD (Gumboro) vaccines: Based on a combination of vaccine virus and specific homologous antibodies in very well defined proportions, these vaccines have the capacity to delay the release, and hence the replication, of the vaccine virus up to an age where MDA level has reached a level that is no longer capable to neutralise it. Because of their reliability and their strong efficacy, in particular in areas where the very virulent form of the disease is present, this new type of IBD vaccine is becoming more and more frequently used all over the world.

• Recombinant (IBD, ND, ILT, AI, etc.) vaccines: These vaccines are made from a gene extracted from a virus against which protection is looked for. This gene, encoding for a protective antigen, is introduced in the genome of another virus used as a carrier (the vector). Indeed, this vector must be apathogenic for chickens like Fowl Pox (FP) virus for example, and preferably not susceptible to homologous MDA, which is the case of the Herpes Virus of Turkey (HVT) also used to protect chickens against the mild forms of MD. The way these vaccines induce protection is something really new and a lot of research work still need to be done until we actually fully understand it. Their capacity to breakthrough MDA is real when HVT is the vector. Besides, since HVT persist forever in the vaccinated animal, long lasting protection is observed. This is very interesting when considering protection against ND.

Increasing efficacy

Recent field trials conducted around IBD vaccination have included very close comparison of efficacy between vaccination at the hatchery and vaccination at farm. Results were just unbelievable. In some organisations, the percentage of not protected flocks, despite a heavy vaccination programme, was as high as 20 to 30%, and sometimes even higher. In hatchery-vaccinated flocks, percentage of protected flocks almost always reached 100%.

For many reasons including reduction of the duration of the growing period for broilers, increasing cost of the work at farm, as well as the recent availability of adapted equipment and new types of vaccines, vaccination at the hatchery is becoming more and more common in the poultry business. It globally helps producers in reducing costs and improving efficacy of vaccine prevention. It is also a field of very active research for vaccines producers and there is no doubt that this is where the future of broiler vaccination stands. Vaccination at the hatchery is a real improvement for vaccine prevention, and this is really a promising way to advance control of diseases.