The egg industry is currently dealing with its fair share of challenges. With EU production outstripping consumption and prices being squeezed, producers are looking for more ways to improve the efficiency of their business.
Egg number and shell quality are always important measures but with many looking to increase the laying cycle of their birds and regular discussions surrounding reaching 500 eggs per bird, the role of layer gut health in production has never been more pertinent.
Egg production for the laying hen is a taxing process in terms of energy expenditure and stress. Creating an egg is a biologically complex process. Initially, the yolk is released from the ovary and passes through the infundibulum, where the outer vitelline membrane is added. While in the magnum, the albumen is secreted. This then passes into the isthmus where the precursors to shell membranes are added. The shell gland is where the egg spends most of its time. This is the point where the shell is formed; consisting of the mammillae, the palisade layer and the transitional vertical crystal layer. The cuticle, a proteinaceous antimicrobial layer, is then added prior to oviposition. The eggshell is mainly composed of calcium carbonate (CaCo3) and protein, and offers the most protection.
It is necessary to define what precisely is meant by ‘eggshell quality’. Generally, a good quality shell is considered to be one that does not crack easily and, as a result, will reduce the number of seconds. However, increasing shell thickness does not necessarily improve quality; it is the structure of the shell that is crucial. Many enzymes and minerals are involved in the creation of the shell structure – the mineral requirement of the bird is met through dietary supplementation. These are then digested, depending on structure, and absorbed in the small intestine via receptor-mediated uptake. If the bio-availability of the minerals in the diet and, hence, the concentration of minerals in the gut lumen is not optimum, then the bird will not have the correct amount of minerals present to create her egg.
Organic chelated minerals
One method for ensuring optimum bio-availability is to use organic chelated minerals in the diet. Multiple studies have shown their benefits on performance and shell quality.
Calcium’s imact on shell quality
Calcium is a crucial mineral component of the eggshell, being the cation of CaCo3. It is often presumed that increasing the amount of calcium in the diet will automatically lead to stronger shells. However, there is a very fine balance to be considered. Calcium, when dissolved in the gastrointestinal system, can interact with other minerals, reducing their absorption. This in turn can have a direct impact on other structural components of the egg, diminishing quality.
In order for the hen to uptake her minerals effectively, she must have a healthy gut. Between 50–80% of the immune system functions in some way through the gut. Such a high immune presence means that it is simple for defences to respond to both actual challenges and things that perhaps should not be eliciting a response.
Extra mucous means less mineral absorbion
Immune response in the gut generally takes the form of inflammation which produces additional mucous layers. Mucous provides an extra barrier for the minerals to pass through before being absorbed. This means that if an inflammatory response is underway, it is unlikely that the bird will receive its full mineral requirement, impacting eggshell structure and thus strength and quality.
Immuse response triggers
Many factors can trigger the immune system, such as mycotoxins, new diets and high levels of potentially pathogenic bacteria, known as dysbacteriosis. Having a balanced microbiome (the microbial population in the gut), will go a long way towards preventing dysbacteriosis and in many studies has been shown to aid in modulating the immune system, reducing the impact on absorption.
Gut Health Special:
Managing gut health is very complex with many parameters to consider. This special issue covering monogastrics and ruminants highlights specie-specific topics.
Microbiome is development
In a natural setting the microbiome is developed from the mother as the chick is raised in the nest. Our modern production systems mean that this does not happen and so the creation and maintenance of the microbiome needs to be taken into account in management practices. Many producers have been successful in improving gut health and the microbiome through the implementation of Alltech’s Seed, Feed, Weed programme to manage the composition of the intestinal microbial community. This involves accelerating the evolution of the microbial community to a steady state and then maintaining the status quo. By seeding the gut with favourable organisms, feeding the favourable organisms and weeding out the unfavourable organisms, this will help to improve shell quality.
Calcium impact on gut health
Overly elevated levels of calcium can also significantly impact gut health. In an aqueous solution, calcium becomes alkaline and so can neutralise the acids produced in the proventriculus and gizzard. These acids are the first step in protein digestion and if this is impaired, protein can pass into the small intestine. Bacteria in the intestine are then able to use this as a substrate for fermentation. Dysbiosis and associated issues can then occur.
The laying hen can naturally continue to produce eggs for many years. However, her peak production will naturally decline with age. Genetic advances in recent years have allowed birds to produce nearly one egg per day, from week 18 to week 75. But, due to the push for large eggs which come at end of lay, this period is now being extended to 80 or more weeks in some cases. As the laying period is lengthened this will put more stress on the bird, as she must create a metabolically rich egg while also maintaining her body weight and dealing with any additional challenges from the environment that may impact the immune system.
Different bird, different egg characteristics
It is worth noting that if the energy requirements of the bird are not being met, at a certain point her body will shut down the reproductive system that was producing the eggs in favour of supporting her body weight and providing energy for vital bodily systems. Maintaining and promoting gut health in flocks increases villi height, reduces villi:crypt ratio and improves tight junctions between cells. Consequently, as already discussed, certain gut health supplements can help support immune function and also promote factors such as villi development. Villi with improved height will have more surface area and, therefore, can absorb more nutrients to sustain the hen for longer laying cycles. Improving tight junctions will prevent bacteria from becoming translocated into the bloodstream. This is a common issue in stressed birds and can lead to a multitude of problems — in the worst case, diseases like Colisepticemia. Disease and minor inflammation in the gut caused by dysbacteriosis will cause energy expenditure on powering the immune system which will prevent the hen from converting that energy into eggs.
As previously noted, producers are coming under pressure. They are looking for ways to help their birds to continue to lay more, ideally from less. Improving the gut health of birds in lay will enable them to absorb a greater proportion of their feed, meaning that less is going to waste in the faeces. Quality food will help layers to produce quality eggs, but the best results come with good gut health. If the bird is not able to absorb the necessary nutrients, her egg production will suffer. Studies have looked at the impact improved gut health has had on laying rate, with benefits seen in laying intensity, egg weight and feed conversion.