How can the risk of disease and parasites be managed in cage-free layer hen housing systems?

Cage-free systems for layer hens include free-range, barn, and aviary housing systems. Cage-free systems are beneficial for hen welfare because hens can move around freely, socialise with other hens, lay their eggs in nests, and have a greater opportunity to express behaviours, such as dust bathing and perching ​[1]​. When cage-free systems are poorly managed, there can be an increased risk of infectious and parasitic disease outbreaks within flocks. Good husbandry and biosecurity management practices are essential to effectively mitigate the risk of disease for hens in cage-free systems.

Why is there a higher risk of disease and parasites in cage-free housing systems compared to cage housing systems?

There is an increased risk of infectious diseases and parasites developing in hens housed in cage-free systems because hens are more likely to come into contact with faeces, litter, other hens, and possibly other animals (e.g., wild birds and rodents) ​[2–4]​. Free-range housing systems have the highest risk of internal parasite infections because hens may ingest these parasites, which are typically found in soil and small insects ​[3]​.

In cage systems, hens are confined to wire cages in smaller groups without litter access and are less likely to come into contact with faeces, so there are fewer ways for disease to develop and spread within a flock. To read more about the significant animal welfare issues with housing layer hens in cages, click here.

Infectious diseases

Infectious diseases can cause symptoms in hens ranging from decreased egg production, lameness, coughing and breathing difficulties, diarrhoea, neurological signs, and sudden death. Some of the infectious diseases recognised to affect hens in Australia include fowl cholera (Pasteurellosis), laryngotracheitis, spotty liver disease (Campylobacter hepaticus), avian influenza, Newcastle disease (Avian paramyxovirus), Marek’s disease, pododermatitis (Staphylococcosis), bacterial salpingitis (Escherichia coli), and coccidiosis ​[2]​.

External and internal parasites

External parasites that can commonly infect hens include red mite (Dermanyssus gallinae) and poultry lice ​[3]​. Internal parasites that can commonly infect hens include various species of Nematodes (i.e., roundworms), such as Ascaridia galli, Capillaria spp., and Heterakis gallinarum and tapeworms (Cestodes) ​[3, 5]​.

How can the risk of disease and parasites be managed in cage-free housing systems?

There is a risk of hens developing disease and parasites in all types of housing systems. Hens with increased stress levels have been shown to have an increased risk of developing most infectious diseases ​[2]​. Stressed hens can also be more infectious at spreading the disease to other hens ​[2]​. While cage-free housing systems can have a higher risk of hens developing infectious diseases and parasites than cage systems, the risk of disease can be effectively addressed with good biosecurity and management practices.

There are several management strategies that have been demonstrated to be effective at mitigating the risk of infectious and parasitic diseases in hens. These strategies include ​[2, 3, 5, 6]​:

• Regular and active monitoring of hens for early identification and treatment of disease.
• Avoiding nutritional deficiencies by providing hens an appropriate diet. Certain supplements and probiotics can help improve the gut microbiota and immune system of hens.
• Appropriate biosecurity practices for on-farm staff, disinfection of equipment that is shared between sheds and farms, and cleaning and disinfection of indoor housing areas between flocks.
• Maintaining good quality litter in a dry and friable condition on the floor of indoor areas.
• Regular faecal egg count assessment of hens in free-range housing systems if there are concerns of any external parasite infections.
• Paddock spelling and rotation, or the use of mobile housing in free-range housing systems to minimise the risk of internal parasites in the outdoor range area.
• Good drainage of the outdoor range area and preventing access to any muddy or wet areas on the range in free-range housing systems.
• Vaccination programs in the flock to effectively prevent and control certain infectious diseases.
• Antibiotic treatment may be required in some situations to control symptoms of an infectious disease however it does not necessarily prevent transmission of the disease. Antibiotics for layer hens should only be used for therapeutic purposes and under the advice of a qualified poultry veterinarian.
• Deworming and targeted anthelmintics treatment to treat internal parasites infections under the advice of a qualified poultry veterinarian. Wider anthelmintic resistance testing would be useful to provide information on the effectiveness of commonly-used anthelmintics in poultry in Australia.