The liver is essential to obtain good productive performance in layers.

INTRODUCTION: ROLE OF THE LIVER IN POULTRY

The liver has an essential role for the animals since it performs basic functions such as detoxification of the organism and synthesis of proteins, lipids, and carbohydrates.

In poultry, maintaining the liver in optimal conditions is imperative to obtain good productive results, because it is in charge of the synthesis of the necessary components to produce meat and eggs.

This article explains the relation between liver functions and egg production to understand the role of this organ in layer and breeder hens.

LIVER FUNCTIONS

The liver has three main functions: detoxification, synthesis and metabolism, and storage of multiple substances.

• Detoxification

Many toxic substances in the organism need to be metabolized (transformed) before they are eliminated. The liver does so to external agents, such as pathogenic bacteria or drugs, and internal substances, such as old blood cells.

The liver is considered the entrance filter for the molecules absorbed at an intestinal level, since it cleanses the toxic substances that the animal ate with the feed to prevent their arrival to blood circulation.

For this reason, the liver is constantly in contact with toxic substances that can affect its physiology. If this happens, the capacity to protect and detoxify the organism decreases and the animal becomes more exposed to hepatotoxic agents.

• Synthesis and metabolism

Carbohydrate, lipid and protein synthesis takes place in the liver, which is also in charge of the synthesis of coagulation factors and bile production and secretion.

Protein and lipid synthesis is particularly important to ensure egg production and quality, essential components for the yolk and the egg white.

Moreover, the production of muscle and immune effectors are tightly related with the liver physiology, since proteins are the main component of meat and immunoglobulins.

For this, any factor that affects the liver function will negatively impact on the laying rate and egg quality. In addition, it will also increase the probability to suffer from infections due to liver-related immunodeficiency.

• Storage function

The liver storages some vitamins (A, D, K and E) and minerals necessary when the levels obtained from the feed are insufficient. It also storages glycogen, which represents an important energy source for the organism. Energy storage is important in laying hens in intensive production systems because of their higher energy requirements.

HEPATOTOXIC AGENTS

Since the liver filtrates the components absorbed in the gut and metabolizes and cleanses toxic substances and residues, it is constantly in contact with toxic substances that can affect its physiology.

• Drugs

Among the hepatotoxic substances are some drugs frequently used in poultry, such as antibiotics and coccidiostats. These products represent a problem because, apart from their hepatotoxicity, they cause the development of resistances in microorganisms, making their elimination much more difficult.

• Mycotoxins

The liver is the first defense line against infections because of its filtration function and the production of immune precursors. For this, it is often damaged by microorganisms that can multiply in the organ or in the biliary ducts. It can also be affected by toxins produced by these pathogens, which come from the digestive tract.

Hens suffering from liver disorders need to receive an effective treatment. Once the infection is solved, it is unlikely that they recover the expected performance results, because, especially if the infection was severe, the liver does not completely restore its functions.

• Liver overstraining

The effect of hepatotoxic agents gains importance nowadays because the liver, in intensive production systems, is under constant stress. This is due to the high production levels in commercial layers, which increase the need for lipids and proteins. This pressure on the organ can cause cell weakening and a decrease of the capacity to perform its functions. Hepatocyte degeneration can lead to a complete loss of function, which makes the liver much more likely to get infections.

TOOLS FOR LIVER PROTECTION

Despite the wide variety of factors that threaten the liver, there are some key tools that help to maintain its function even in highly productive animals that are constantly under stress.

The tools described below give solution to the five threatens described in the last section.

• Natural products to replace drugs

The use of antibiotics and anticoccidial drugs, among others, is getting limited in poultry. This is because of the toxic effects some of them have and, also, due to the development of microbial resistances and the presence of residues in animal products. The latter is particularly important in layers because the egg is a product for human consumption, and the presence of residues can increase the prevalence of multi-resistant strains in human medicine.

There are different solutions to replace these drugs, such as pronutrients that act as intestinal conditioners and optimizers. These are molecules found in plants that naturally stimulate the physiology of the organs by improving cell physiology.

Since their mechanism of action is not based on pathogen elimination, they do not cause the development of resistances. Neither do they leave residues in animal products.

Intestinal conditioners improve gut mucosa’s physiology to strengthen it and make it capable of preventing pathogen invasions. They can replace antibiotic growth promoters: the gut mucosa will already be in an optimal status and able to control pathogen overgrowth.

Intestinal conditioner pronutrients stimulate gut local immunity, so that the animal is ready to eliminate any protozoon, such as coccidia, that contacts the digestive mucosa.

Thanks to the replacement of drugs with these natural products the liver gets less exposed to hepatotoxic agents.

• Mycotoxin binders

There is a broad variety of molecules with mycotoxin binding activity that are used to prevent the negative consequences of these toxins on the liver, the digestive system and, generally, on the organism.

Choosing the best mycotoxin binder is essential to achieve good protection levels. The factors to consider are the spectrum of action, which must be as wide as possible; its efficacy in the target species, the minimum effective dose and its specificity, which means the capacity of the binder to bind mycotoxins, exclusively.

Is it difficult to find a mycotoxin binder that complies all these specifications? There are only few molecules that comply with all of them, such as Silicoglycidol, a patented molecule based on natural silicates modified to increase the adsorption surface, spectrum of action and decrease the binding of other diet components, such as nutrients.

• Antioxidants

It is necessary to add antioxidants to feed to prevent the formation of free radicals, which are dangerous for the liver and other organs. This is particularly important in diets with a high fat content, and they also prevent the oxidation of vitamins and carotenes.

Natural antioxidants, such as selenium and vitamins E and C, are recommended because they do not leave residues in animals. Other antioxidants such as ethoxyquin, BHT and BHA are less advisable because they accumulate in fat and can reach toxic concentrations.

Antioxidants have a positive effect on egg internal quality, too. They slow down oxidation of egg components, such as the lipids in the yolk.

• Balance of the gut flora

It is essential to prevent the presence and overgrowth of microorganisms capable of causing an infection, to prevent systemic disorders.

Some of these microorganisms are transmitted vertically and cause infections in the embryo. These animals will not be able to reach their maximum productive potential because the microorganisms can multiply in their digestive system, the liver and other organs and affect their functioning.

To prevent these situations, natural products based on the synergistic combination of cimenol ring and citric acid are highly recommended. They are effective against pathogenic microorganisms present in the digestive tract, because of their bactericidal and fungicidal activities, and safe for the beneficial flora.

This combination can be administered to layers, continuously to decrease the percentage of dirty eggs and prevent infections such as necrotic enteritis caused by Clostridium perfringens, a bacterium that produces toxins that can damage the liver. In breeders, continuous administration decreases the vertical transmission of infections such as infectious toxic hepatoenteritis. In this last case, the sacrifice of affected breeders is also recommended, because their productive performance will not be the desired ones.

The administration of cimenol ring and citric acid in specific productive periods can help to balance the gut flora in stressful situations, or during the most challenging weeks. They also work as a treatment for gut infections when administered in the drinking water, to avoid a future infection of the liver.

• Liver conditioner pronutrients

Pronutrients that target the hepatocytes can help to fight liver overstraining. They stimulate cell functioning and improve liver protection and regeneration.

They are especially recommended after the peak, to prevent liver disorders such as the fatty liver syndrome. Another option is to administer them continuously during all the productive period to improve egg internal quality, since, as mentioned, it greatly depends on the liver.

CONCLUSIONS

Egg production greatly depends on the liver. This organ performs essential functions for the organism and synthesizes components of the yolk and the egg white.

The liver function should be optimized in intensive farms, where egg production is so high that the organ in constantly stressed, which makes it prone to suffer the consequences of toxins and infections.

For this, it is essential to use high-quality ingredients, additives that protect it from hepatotoxic agents, and products composed of liver conditioner pronutrients, molecules from a natural origin that stimulate and regenerate liver physiology.

Adding these substances in the diet has been proved effective to improve the laying rate and egg internal quality. They also have other advantages, such as they do not leave residues in eggs and do not cause the development of microbial resistances.

Biovet, S.A. markets the additives mentioned in the article as follows: Alquernat Nebsui (intestinal conditioner), Alquernat Zycox (intestinal optimizer), Alquerfeed Antitox (Silicoglycidol), Alquernat Antiox (natural antioxidants), Alquermold Natural (natural biocide) and Alquernat Livol (liver conditioner).