Vaccine strategy in cage-free layers requires new mindset
By Daniel Wilson, DVM
Founder and Lead veterinarian
Wilson Veterinary Company
As the US layer industry adopts cage-free production, producers are learning that disease problems can differ compared to those in caged layers. The vaccination strategy needs to be adjusted accordingly but there can be hesitancy to change.
To help layer producers devise a well-rounded vaccine program for cage-free birds, I often refer back to my three least favorite sayings.
‘Those convinced against their will are of the same opinion still’
To make alternative production system programs work, we have to get past preconceived notions of how caged bird health traditionally has worked. We need to put our brains to use tackling new challenges.
One of the best ways to get forward progress in an operation, as they say in 8th grade math class, is to “show your work.” Convincing a layer producer to change their vaccination program often requires demonstrating the need to change and potential return on investment. There are several ways this can be accomplished:
- Routine diagnostics, such as serology, help identify disease challenges as much as they help rule disease challenges out. We have had farms convinced that egg production and shell quality is adversely affected by infectious bronchitis virus (IBV), only to find this disproved by serology and other routine diagnostics. IBV is not always the sole offender in shell quality effects. We often find a variety of low-hanging fruit that are affecting external or internal egg quality. There are a variety of other problems including mycoplasmas, management and nutritional effects that can also affect egg quality.
- Targeted diagnostics, such as cultures and sequencing of isolates, can identify pathogens affecting layer flocks. These are important methods of identifying disease challenges in cage-free birds as they provide solid proof. Once problem organisms are identified or quantified, an action plan can be put in place.
Here’s an example: Historically, Escherichia coli was exclusively responsible for gross lesions of “peritonitis” or septicemia in cage egg production. However, although E. coli is still the most common cause, it’s not the only potential cause. Appropriate culture work is important to keeping the health program on the right track. Decreased options or antibiotic availability makes correct diagnosis and pursuit of effective interventions and alternatives even more important.
- Routine posting sessions of mortality and wellness in birds are essential if appropriate interventions are to be implemented. What are the typical causes of day-to-day clinical health issues contributing to mortality? Don’t wait for large mortality events or until something is a serious problem. Small day-to-day challenges over the life of a flock add up to much larger cumulative problems with poor livability or hen-housed egg numbers.
- Not every health challenge will be readily evident, characterized by poor egg production or increased mortality. Individual birds can have subclinical disease or there may be low-level, nagging mortality just slightly over normal yet under genetic standards. We see this often with wet pox and infectious laryngotrachetis (ILT) viruses that can persist in flocks for days, weeks, or months; there is a low-level challenge rolling through the house, hitting unvaccinated or poorly vaccinated birds. We also know that mycoplasmas such as Mycoplasma gallisepticum can be very sneaky. There is a reason it is referred to as chronic respiratory disease in layers – the changes can be subtle over time, gradually stealing egg numbers from an otherwise apparently normal flock. Without proper posting of mortality and review of flocks, it can be easy to overlook.
Takeaway: Gold-standard veterinary health monitoring and investigation — showing the work — provides the encouragement needed to make appropriate changes. Those not convinced will be left behind to potentially struggle with chronic flock health challenges.
‘It is what it is’
When producers encounter new health challenges in cage or cage-free production, they too often wash their hands of the situation as though there were nothing that could be or have been done differently. The mantra “it is what it is” comes into play. There are sometimes extenuating circumstances — avian influenza is one example. But in most cases, the better approach to new health challenges is careful consideration of what could have or should have been done to mitigate the problem.
Universal pullet programs certainly are simpler to implement, but they don’t necessarily work for alternative production systems.
Birds with floor and litter access will eventually have health challenges different from what we see in caged systems and those health challenges will vary greatly from one farm to the next, even within the same company. One farm may require vaccination against infectious coryza while vaccination against erysipelas is needed at the farm nextdoor. Some premises may have more challenges with internal and external parasites, such as roundworms, yet others do not. Trying to make one master pullet program to fit all these operations is like putting a square peg in a round hole.
Takeaway: The days of universal pullet vaccination programs are behind us. Vaccination programs need to be individualized to meet the disease challenges on each farm.
If it ain’t broke, don’t fix it
This is similar to being convinced against one’s will: It’s leaving a health problem dormant, which can put producers behind the ball when it comes to mastering cage-free flock health.
New vaccine technology, new vaccine application methods and sometimes the use of autogenous vaccines may be foreign to some producers but progressive, cage-free layer producers who take advantage of these options are highly likely to have more success.
Recombinant vaccines are among the newer vaccine technologies and are already in use. They can have a huge, positive impact on immune and pullet development. Many producers in the US egg industry are already finding great success with recombinants such as herpesvirus of turkey (HVT) vaccines that protect against Marek’s disease as well as other diseases such as infectious bursal disese and Newcastle disease. Recombinant vaccines administered at the hatchery have a variety of benefits such as accuracy and timing of administration.
Any vaccines that can be shifted to hatchery administration allow for greater likelihood of uniform flock coverage and enhanced immune response. As more recombinant products appear on the market, producers can expect fewer field disease challenges and the need for field vaccination.
Takeaway: Never let health programs stagnate until a problem arises. Consistently plugging in new options or methods can help maximize pullet development and immunity, improve flock performance and producer return on investment. That’s a lot easier than fixing the vaccine protocol after it breaks.
Editor’s note: The opinions and advice presented in this article belong to the author and, as such, are presented here as points of view, not specific recommendations by Poultry Health Today.
Posted on November 16, 2022