Reliable vaccination programmes will be required to support layer persistency. This was the message from poultry vet Andrew Walker, from Slate Hall Veterinary Services, speaking at Cargill’s recent poultry workshops held in Norwich, Shrewsbury and Penrith over the summer.
“Ensuring birds were protected to the end of lay at 100 weeks, as opposed to between 75 and 80 weeks, was a challenge that needed to be met,” says Walker.
“Disease prevention and eradication are just two reasons for vaccination. Preventing pathogen spread and food safety are also important.”
Vaccination programmes have been highly successful in controlling diseases, like salmonella, that pose a threat to human health, and in creating a fire break for disease spread.
“And these are often part of assurance schemes that producers must adhere to,” he says.
Vaccinating poultry should be cost-effective. “In fact, it’s relatively inexpensive to vaccinate poultry flocks,” he says, adding that many vaccines are approved for use up to 60 weeks in lay. “The challenge is to get approval up to 100 weeks, which would require data and evidence, and this can be expensive.”
Vaccination aims to create active immunity and prime the system. The effectiveness of a vaccine will reduce over time. “So, immunity can be much lower towards the end of lay.”
Walker explained that a host of factors affect immunity in layers. Different modes of action and administration methods have an impact, with the latter depending on the rearing system.
“But, in general, a good drinking water vaccination is better than a bad spray particularly, for example, in multi-tier systems where there is a lot of equipment. And a vaccination gel in a hatchery works well, as chicks will ingest a lot of vaccine.”
Vaccine efficacy relies on good storage protocols and can be affected by poor storage. “Vaccines must be kept in a cold chain and avoid UV and daylight.”
Improvements in pullet management will support successful vaccination programmes. “As a sector, we’ve not been so good at investing in pullets, and weak links in management can affect immunity, such as dirty water or respiratory issues.”
He also highlighted the need to minimise stress and consider age and time of vaccination and scheduling vaccines to protect bird welfare.
“There are limited opportunities to vaccinate once the birds are in lay, so we have to work with pullet rearers to plan vaccinations within the rearing period.”
Another consideration is the calorific cost of vaccinating. Mounting an immune response can use between 25% and 30% of daily calorie intake. “Three killed vaccines at the 12-week rearing period, for example, will therefore take its toll on growth rates. And some vaccines will out-compete others,” says Walker.
Each poultry unit will have its own vaccination programme that requires regular reviews. “It needs to take account of the site and its history, national and local risks, and on-farm assurance requirements,” he says. “And we have to be aware of new risks and challenges.”
Looking at the disease risk in layers aged between 70 and 100 weeks old, and based on current data, he said he wouldn’t expect to see a huge amount of challenge from Marek’s disease, and after a spike in salmonella between 2018 and 2023, incidence is now extremely low and less than 1%.
“Vaccination controls salmonella in poultry well,” he says, “but longer living flocks are more at risk – vaccination gets us so far, but hygiene and biosecurity are vital.”
With no in-lay vaccine currently available, Walker notes the excellent protection afforded by a combination of live and killed vaccines given in the rearing period. “But the use of these comes down to cost and management. Most still use just a live vaccine and this has worked well so far.”
“E coli is an infectious disease that is always a risk to poultry, and most layers will die from it eventually,” he adds. “A combination of live and killed vaccines in the rearing period protects birds, and there is safety data from using an in lay live vaccine with very good anecdotal experience.”
Multiple live vaccines are typically given in rear to protect birds from a range of strains of virus causing Infectious Bronchitis (IB) – a costly disease that reduces egg numbers and egg quality and increases the number of false layers. Egg production drops can last in total for approximately six weeks.
Most flocks are also vaccinated at transfer with a kill vaccine to prolong the duration of protection.
“There is an in-lay vaccination for IB and this is now used more frequently. While an IB challenge will still affect production, the impact is significantly reduced in well vaccinated flocks.”
Flock health and disease prevention is vital in ensuring successful and efficient layer persistency. “Although we don’t have vaccine approvals beyond 76 weeks in lay for many vaccines, a well-planned vaccination programme supported by high hygiene, biosecurity and management standards should mitigate the risk of disease outbreaks.”