The role of gut health in cage-free egg production
By: Harriet Walker, poultry specialist, Alltech
The European Commission estimates that 50% of egg production has already moved to cage-free. For those farmers and integrators now working on their transition plan, it is time to think about new challenges or challenges that may be heightened with this new production system.
Cage-free housing systems increase the ability of the birds to mix, move and have contact with litter and the outside environment, leading to several potential gut health issues, including:
· Antibiotic use
· Feed consumption
· Disease control
· Wet litter
Antibiotic use in poultry
It has been shown that there is more exposure to potential disease-causing organisms in cage-free environments, contributing to higher mortality levels. The higher mortality will negatively impact bird health and welfare, food security and egg production sustainability, resulting from the reduced productive output. To support performance and reduce mortality when changing to a cage-free system, farmers may turn to antibiotics. However, the use of antibiotic growth promoters (AGPs) and the associated antimicrobial resistance have been highlighted as a global health problem for humans and animals. Therefore, with more birds being raised in conditions that favour the spread of pathogens, there is a need to maximise performance in cage-free systems to avoid the use of AGPs. One way to help reduce AGPs is to improve and support the bird’s gut health and microbiome through the “Seed, Feed, Weed” programme.
Seed: Seeding the gut with favourable organisms
To support gut and microflora development in the young bird, they must be exposed to favourable organisms as early as possible. This can be done via a probiotic that 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 villi height and increase the surface area of the gut, but it can also improve the bird’s ability to defend against pathogenic bacteria.
Feed: Feeding a favourable environment
It is vital that, once established, this good microflora population is maintained. This can be challenging in a cage-free housing situation, as the birds have more opportunities to pick up pathogenic bacteria that can colonise the gut and increase the risk of enteritis, reduced performance and health and welfare issues. To help the bird sustain a good microflora population, a buffered weak organic acid compound can be incorporated in the feed, helping to lower the pH in the GI tract. A low GI tract pH reduces the growth of pathogenic organisms such as Clostridia and Campylobacter, which are intolerant to acidic conditions. Feeding a buffered weak organic acid helps the favourable organisms reach the small intestine, promoting the growth of beneficial microflora.
Weed: Weeding out unfavourable organisms
With the increased exposure to potential disease-causing organisms in cage-free systems, it can be helpful to add a supplement to the feed to weed out and reduce colonisation of the gut by pathogenic bacteria. Actigen® is a second-generation, unique bioactive product derived from Saccharomyces cerevisiae, selected by Alltech and isolated to create a more effective product in order to optimise gut health. For a pathogen to cause disease, it first needs to adhere to the gut epithelial lining via type-1 fimbriae projections. Once attached, the pathogen can replicate, which can then lead to inflammation, villi damage and reduced nutrient absorption. By binding to the type-1 fimbriae, Actigen can inhibit attachment by pathogenic bacteria and is preferable to antibiotics that are non-specific and destroy beneficial organisms as well as pathogens. It has been shown to improve absorptive capacity by increasing villi height and surface area and enhancing villi:crypt ratio, enabling improved absorption of nutrients and, thus, improved performance. It also helps maintain microbial diversity and promote good gut health and the animal’s natural defences.
Feed intake in poultry
Moving birds to a cage-free system, such as a free-range facility, allows the layers to exhibit several natural behaviours that are limited in a cage system. These include running, flying, dust bathing, beak cleaning, preening and stretching. This increased movement can raise the metabolic energy needed by the hen, which can be further affected by adverse weather conditions. The bird will need to increase its intake to meet this heightened energy requirement. Otherwise, energy will be diverted away from maintenance and egg production. This means it is vital that the bird has optimum gut health, maximising its intestinal surface area to allow for efficient nutrient absorption and improved feed utilisation. An activated immune system requires both energy and nutrients, which are repartitioned from production. With the greater chances of cage-free birds encountering pathogenic bacteria, the bird must have optimum gut health and microbiota, as they play a role in modulating the immune system by preventing mucosal infections.
Wet litter in poultry
In cage-free systems, layers have more contact with litter than when housed in cages. This means that wet litter becomes a greater concern. Wet litter and high ammonia content can lead to footpad dermatitis and bumblefoot, a painful footpad infection. While uncommon in furnished cages, the
frequency of bumblefoot can be several times higher in litter-based houses. Many factors may contribute to wet litter, such as:
· Digestive upset
· Nutritional imbalance
· Drinker spillage
· Inadequate ventilation and humid weather
· Both non-pathogenic and pathogenic agents, which can cause diarrhoea
Therefore, it is vital that the underlying cause is identified and corrective actions are implemented as soon as possible to return the bird to optimal gut health. Mycotoxins, coccidiosis and dysbacteriosis can reduce gut integrity and damage the intestinal epithelium, leading to decreased absorption and digestion of nutrients and increased intestinal barrier permeability, which can lead to wet litter. When the gut structures are damaged, the undigested nutrients can pass into the caeca, providing a nutrient source for the microbial population that resides there. Often, potentially pathogenic organisms are found in the caeca, and this nutrient source allows them to replicate to numbers large enough to cause imbalances in the microbiota, which impacts performance and litter conditions.
Poultry disease control
Causes and treatment of coccidiosis in poultry
Coccidiosis is an enteric condition caused by protozoa of the species Eimeria, which infects the intestinal lining and causes damage that enables other pathogenic bacteria to proliferate. The symptoms of coccidiosis are:
· Bloody diarrhoea
· High mortality
· Poor growth/weight gain
· Drops in egg production
Coccidiosis can be controlled via ionophores and chemical compounds added to the feed that inhibit oocyst development. However, resistance and tolerance can develop with these anticoccidials, so they need to be used in cycles to be effective. Another way to control coccidiosis is via a coccidia vaccination programme that develops immunity against coccidiosis. Having increased access to litter increases the exposure of cage-free birds to coccidia. However, layers are commonly vaccinated for coccidiosis, especially in cage-free systems. Therefore, they have immunity by the time they are on the layer farm.
Causes and treatment of intestinal worms
Intestinal worms can be an issue when birds have contact with grass, soil and faeces. Therefore, exposure to intestinal worms is likely in a barn or free-range system. Worms damage the bird's gut, resulting in reduced performance. Three main worms that may cause problems in cage-free birds are:
· Caecal worms
Causes and treatment of Blackhead disease
Worms can carry other parasites, like Histomonas, which causes blackheads. Blackhead disease (histomoniasis) is a pertinent poultry disease caused by a protozoa that can be spread to the bird through roundworms. Healthy birds become infected when they eat food, invertebrates (such as earthworms) or bird droppings contaminated with the protozoa. Direct bird-to-bird transmission can also occur within a flock. Chickens infected with blackhead disease are usually listless and have
drooping wings, unkempt feathers, yellow droppings and reduced egg production. It is essential that birds infected with blackheads are wormed to kill the worms. It is vital that birds are monitored for worms and wormed effectively before moving them to lay accommodation, prior to the onset of lay and during lay to reduce build-up on pasture.