The role of gut health in cage-free egg production

Cageless housing systems increase the ability of birds to mix, move, and come into contact with litter and the outside environment, leading to several potential gut health issues, including antibiotic use, consumption food, disease control and wet litter.

Use of antibiotics

European Commission legislation to produce all eggs from alternative non-cage housing systems will increase the number of laying hens reared in non-cage systems over the next few years. It has been shown that there is more exposure to potentially pathogenic organisms in these environments, which contributes to higher levels of mortality than in cage systems. The higher mortality will have a negative impact on bird health and welfare, food security and the sustainability of egg production, resulting in reduced production. To support performance and reduce mortality when switching to a cage-free system, farmers can turn to antibiotics.

However, the use of growth promoting antibiotics (AGP) and associated antimicrobial resistance has been highlighted as a global health problem for humans and animals. Therefore, with more birds reared under conditions that favor the spread of pathogens, there is a need to maximize the performance of non-cage systems to avoid the use of AGP. One way to help reduce AGP is to improve and support the gut health and microbiome of the bird through the “Seed, Feed, Weed” program. This includes seeding the gut with favorable organisms, providing a favorable environment for these organisms, and eliminating unfavorable organisms.

Cageless housing systems increase the ability of birds to mix, move, and come into contact with litter and the outside environment, leading to several potential gut health issues. Photo: Jack Caffrey

Development of microflora

To support gut and microflora development in the young bird, it should be exposed to supportive organisms as early as possible. This can be done via a probiotic which helps the bird develop a diverse and balanced microflora population, promoting gut health and therefore better nutrient digestibility and absorption, immunity and performance. Not only does a good microflora population improve villus height and increase gut surface area, but it can also improve the bird’s ability to defend itself against pathogenic bacteria.

It is vital that – once established – this good population of microflora is maintained. This can be difficult in a non-cage housing situation, as the birds have more opportunity to pick up pathogenic bacteria which can colonize the gut and increase the risk of enteritis leading to reduced performance, as well as health problems and well-being. To help the bird maintain a good population of microflora, a buffered weak organic acid compound can be incorporated into the diet, helping to lower the pH in the gastrointestinal (GI) tract. A low pH of the gastrointestinal tract reduces the growth of pathogenic organisms such as Clostridia and Campylobacter which do not tolerate acidic conditions. Feeding a buffered weak organic acid helps friendly organisms reach the small intestine, promoting the growth of beneficial microflora.

Supplement feeding

With the increased exposure to potential pathogenic organisms in cage-free systems, it may be useful to supplement the diet to eliminate and reduce colonization of the gut by pathogenic bacteria. Actigen is a unique second-generation bioactive product derived from Saccharomyces cerevisiae, selected by Alltech and isolated to create a more effective product for optimizing gut health. For a pathogen to cause disease, it must first adhere to the epithelial lining of the gut via type 1 fimbriae projections. Once attached, the pathogen can replicate, which can then lead to inflammation, villus damage and reduced nutrient absorption.

By binding to type 1 fimbriae, Actigen can inhibit the attachment of pathogenic bacteria and is preferable to non-specific antibiotics which destroy beneficial organisms as well as pathogens. It has been shown to improve absorptive capacity by increasing villus height and surface area and improving the villus:crypt ratio, allowing for better nutrient absorption and therefore improved performance. It also contributes to the maintenance of microbial diversity and promotes good intestinal health and the natural defenses of the animal.

Food consumption

Moving birds to a non-cage system, such as an outdoor facility, allows layers to exhibit several natural behaviors that are limited in a cage system. These include running, flying, dust bathing, beak cleaning, preening and stretching. This increased movement can increase the metabolic energy needed by the hen, which can be further affected by adverse weather conditions. The bird will need to increase its feed intake to meet this increased energy requirement. Otherwise, energy will be diverted from maintenance and egg production. This means that it is vital that the bird has optimal gut health, maximizing its gut surface area to allow for efficient nutrient absorption and better feed utilization. An activated immune system requires both energy and nutrients which are distributed from production. With the greatest chance of cage-free birds encountering pathogenic bacteria, the bird must have optimal gut health and microbiota as they play a role in modulating the immune system by preventing mucosal infections.

Intestinal worms can be a problem when birds come into contact with grass, soil, and feces.  Photo: Jack Caffrey
Intestinal worms can be a problem when birds come into contact with grass, soil, and feces. Photo: Jack Caffrey

Wet litter

In non-cage systems, laying hens have more contact with litter than when housed in cages. This means wet litter becomes a bigger concern. Wet litter and high ammonia can lead to footpad dermatitis and bumblebee foot, a painful footpad infection. Although rare in furnished cages, the frequency of bumblebees can be several times higher in litter houses. Many factors can contribute to litter wetness, including digestive disorders, nutritional imbalance, disease, spilled waterers, inadequate ventilation, and wet weather. Non-pathogens and pathogens can cause diarrhea and lead to wet litter. Therefore, it is essential that the underlying cause is identified and corrective measures implemented as soon as possible to return the bird to optimal gut health. Mycotoxins, coccidiosis and dysbacteriosis can reduce intestinal integrity and damage the intestinal epithelium, leading to decreased nutrient absorption and digestion and increased intestinal barrier permeability, which can lead to wet litter. When intestinal structures are damaged, undigested nutrients can pass into the caeca, providing a source of nutrients for the microbial population residing there. Often, potentially pathogenic organisms are found in the caeca and this nutrient source allows them to replicate in large enough numbers to cause imbalances in the microbiota, which then impacts litter performance and conditions.

disease control

Coccidiosis is an enteric disease caused by protozoa of the species Eimeria which infects the intestinal mucosa and causes damage that allows other pathogenic bacteria to proliferate. Symptoms of coccidiosis are bloody diarrhea, dehydration, lethargy, high mortality, poor growth/weight gain and decreased egg production. Coccidiosis can be controlled via ionophores and chemical compounds added to food that inhibit oocyst development. However, resistance and tolerance can develop with these anticoccidials, so they must be used in cycles to be effective. Another way to control coccidiosis is through a coccidia vaccination program that builds immunity against coccidiosis. Having increased access to litter increases the exposure of uncaged birds to coccidia. However, layers are routinely vaccinated against coccidiosis, especially in non-cage systems. Therefore, they will be immune the moment they are in the layer farm.


Intestinal worms can be a problem when birds come into contact with grass, soil, and feces. Therefore, exposure to intestinal worms is likely in a barn or outdoor system. The worms damage the bird’s gut, reducing its performance. The three main worms that can cause problems in cage-free birds are roundworms, hairworms, and caecal worms.

Worms can carry other parasites, such as Histomonas, which causes blackheads. Black spot disease (histomoniasis) is a relevant poultry disease caused by a protozoan that can be transmitted to the bird by roundworm. Healthy birds become infected when they eat food, invertebrates (such as earthworms), or ingest bird droppings contaminated with protozoa. Direct bird-to-bird transmission can also occur within a flock. Chickens infected with black spot disease are usually listless and have droopy wings, neglected feathers, yellow droppings and reduced egg production. It is essential that birds infected with black spots are dewormed to kill the worms. It is essential that birds are monitored for worms and effectively wormed before moving them to laying housing before lay begins and during lay, to reduce accumulation on pasture.

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