FUDS: An Emerging Health Challenge in Cage-Free Systems
- July 7, 2026
- News
By Brian Dirks, Ph.D., Director – Global Research & Innovation, Poultry
As poultry production systems evolve, flocks face increasingly complex health challenges, often driven by coinfections involving opportunistic pathogens. In these situations, many bacteria that are normally present in the bird or its surroundings and are not inherently harmful can become problematic when birds are exposed to stress, environmental pressure, or breakdowns in physical barriers.
Focal ulcerative dermatitis syndrome (FUDS) is one example, highlighting how opportunistic organisms can transition from part of the normal microbial population to a driver of significant health challenges. However, evidence suggests that promoting gut health through the use of direct-fed microbials (DFM) could help alleviate difficulties.
Defining FUDS
FUDS is an emerging and sporadic disease associated with Staphylococcus agnetis that affects cage-free laying flocks. Infected birds experience spontaneous lesions on the back that grow over time, exposing the tissue beneath. Once lesions develop, they create opportunities for secondary infections caused by other opportunistic pathogens, such as E. coli. FUDS and its related complications can result in increased FCR, decreased egg production, septicemia, and a cumulative mortality rate as high as 50%.
While cases of FUDS have been reported as early as 2009, primarily in brown egg layers, the number of incidences has been steadily rising. This likely relates to the growing number of cage-free flocks in the US, as cage-free birds have a substantially higher exposure to bacterial challenges. Now, even cage-free white layers have been associated with the disease. Currently, FUDS incidences are relatively contained within specific geographical areas, but further expansion of cage-free production throughout the country may cause this area to expand as well.
The Role of Staphylococcus agnetis
Staphylococcus agnetis, like many Staphylococcus species, is commonly found throughout poultry environments (litter, nest boxes, etc.) and can be part of the natural microbial flora of healthy poultry, appearing both on skin and in mucosal membranes. However, as an opportunistic pathogen, it can cause disease when the bird’s immune system is stressed by other clinical or subclinical disease or when the physical skin barrier is compromised. Since FUDS causes skin lesions, it presents the ideal conditions for Staphylococcus agnetis to cause health problems.
How to Support Birds Through FUDS Incidences
A licensed veterinarian can properly diagnose and prescribe antibiotics to treat bacterial infections like FUDS; however, many layer producers prefer to use antibiotic alternatives to address these types of disorders. Proper management and focus on overall flock health, including gut health, are always good practices to help reduce disease and secondary challenges in layer flocks, but research has uncovered other options. Published evidence suggests that DFMs can have a positive impact against Staphylococcus agnetis, with Bacillus pumilus proving to be particularly effective.
Case Study: Effectiveness of a DFM to Support Laying Hens During a FUDS Challenge
A cage-free layer flock of about 20,000 brown layers around 61 weeks of age was experiencing FUDS-associated mortality (roughly 40 birds per day). A random survey of 50 birds showed nine asymptomatic birds with some level of FUDS lesion. A treatment of a six-strain DFM product (four strains of Bacillus subtilis and two strains of Bacillus pumilus) was delivered via water for a pulse of five days with product and two days without.
After the fifth day of treatment, total mortality was reduced by half, to about 20 per day. At the start of the second round of pulsing, mortality was reduced further to around 16 per day, with a random bird survey showing only three of 50 asymptomatic birds with lesions. Before the end of the second round of product, total mortality had reduced to seven per day, and FUDS lesions in the flock were almost fully eliminated. This reduction of mortality, elimination of existing FUDS lesions, and lack of new lesions developing continued for weeks after initial treatment.
Key Takeaways
FUDS can be a devastating disease for a layer flock, causing high mortality and the potential to reduce production and increase FCR. FUDS represents more than a single disease challenge. Rather, it reflects a broader reality: Flock health today is increasingly influenced by opportunistic pathogens and secondary infections rather than a single primary cause. Therefore, as production systems change, managing these challenges requires a more complex approach that supports the bird’s overall resilience.
The case study presented is a prime example of how Bacillus-based DFMS, particularly those containing Bacillus pumilus, can support flocks during a FUDS challenge. These DFM products help promote a healthy intestinal microbiome and a more favorable environmental microbiome, reducing stress and allowing birds to overcome FUDS infections.
Want to learn more about how DFMs can help support poultry flock health?