Importance of Liver Health in Egg Production

Prof. Dr. R.N .Sreenivas Gowda*

Poultry is reared for egg and meat production.  The maintenance of its overall health depends on the health of each and every organ of the body but, the Liver health is very important for egg production, as it is involved in the synthesis of the nutrients present in the egg yolk, albumin and in the formation of the eggshell.

The liver is one of the most metabolically active organs in the bird and its function can be altered when the bird is exposed to toxic compounds such as mycotoxins, which is more frequent in birds with long lifespans, such as egg layers and breeders.

To prevent liver challenges, it’s important to first understand what a healthy liver looks like upon necropsy so that we can spot challenges and make appropriate adjustments.

The liver of poultry is a relatively large organ in their body, and it is located in the lower part of the abdominal cavity, the right leave is larger than the left, and the gallbladder is underneath. Poultry livers are special because the bile ducts exist in both sides. And the bile ducts on the left lobe pass directly to the duodenum, while the right lobe pass to the gallbladder and then to the duodenum.

The colour of the  iver is dark brown in color (except just after hatching, where it is yellow).  Any change in the colour indicates disease.The liver color observation should be done within 30minutes post-mortem, otherwise the result could be misleading. Moreover, the method chosen for euthanizing the bird may change the appearance of the liver (if the bird is bled, the liver may appear pale).

Shape and Structure:

• The liver has a flattened, rounded shape, somewhat like a convex lens.
• It’s closely associated with the Proventriculus and spleen.
• It has a thin capsule and indistinct lobation, meaning the lobules (functional units) are not as clearly defined as in mammalian livers.

Lobules:

• The liver is made up of numerous lobules, which are hexagonal in shape.
• Each lobe contains approximately 100,000 lobules(fig.2)
• Lobules are composed of both parenchymal cells (hepatocytes) and non-parenchymal cells.

Bile Ducts: Two bile ducts enter the distal duodenum, one from each lobe of the  liver. The duct from the right lobe is connected to the gall bladder.

Gall Bladder: The gall bladder lies on the right lobe beneath the spleen.

 Function of Liver

The liver is essentially an exocrine gland, secreting bile into the intestine.  But the liver is also — and significantly so — an endocrine gland and a blood filter.  The liver has a diversity of functions not typically associated with glands.  The liver is a metabolic factory, synthesizing and breaking down a variety of substances.  It’s functions include all of the following:

• Metabolism of proteins, fats and carbohydrates, which are necessary for egg yolk formation.
• Storage of glycogen, buffer for blood glucose.
• Synthesis of urea.
• Absorption of fat-soluble vitamins A, D, E and K; storage of vitamin A; activation of vitamin D (related to the metabolism of calcium and eggshell formation) ; activation of vitamin K ; storage of water-soluble vitamins B1, B2 and niacin.
• Metabolism of iron, copper and cobalt.
• Erythropoiesis (formation of red blood cells)
• The liver is involved in the detoxification of the endogenous and exogenous toxins: it transforms non-water-soluble toxins into water soluble waste products that can be excreted through urine.
• Metabolic end products like ammonia and bile pigments
• Contaminants like heavy metals, pesticides, and carcinogens
• Anti-nutrients
• Medicines and antibiotics

The liver is involved in many functions but whenever it is malfunctioning,  birds will be affected by health problems, poor egg quality and low productivity. Therefore, special attention must be paid to liver health, particularly in layers and breeders    during production.

Changes in the liver color or texture, fat deposition, or necrosis may indicate the presence of disease.

The importance of a healthy liver

Liver condition is extremely important for excellent egg production, as the egg yolk is produced by the liver. A healthy liver is linked with a high egg production capacity. The liver is involved in the activation of vitamin D3 and hence affects the calcium metabolism and on the quality of the eggshells.

Egg shell quality and Fatty liver

As mentioned above, the liver has several important functions. One of those functions is activating vitamin D3 (Cholcalciferol) to 25-hydroxy-vitamin D (25-OH-D3 or Calcidiol). 25-hydroxy-vitamin D3 is transferred to the kidneys for the last activation step towards 1,25 dihydroxy-vitamin D (1,25-(OH)2D3 or Calcitriol. The vitamin D3 metabolite Calcitriol stimulates calcium absorption for eggshell formation. Laying hens, that have a fatty liver, often produce eggshells with a poorer eggshell quality.

The liver disease is common because most of the chickens now have excessive nutritrients, coupled with some toxic factors, and some disease sources.

Liver degeneration and bleeding: Liver degeneration, swelling, fragile and fragile with spotted bleeding on the surface. Liver degeneration with swollen, being pale, and brittle, Hepatocyte degeneration and necrosis.

Adenoviral diseases such as Inclusion body hepatitis, Hydro pericardium Hepatitis syndrome. The liver is Significantly enlarged.

Ulcerative enteritis: It is caused by Clostridium coli (also known as Clostridium enterica). The liver has pale yellow spots, and even large irregular yellow necrosis area or formed scattered gray or yellow necrotic lesions. Liver pathological changes vary from mild yellowish speckle necrosis to large irregular necrotic areas at the margins.

Necrotic enteritis:  Intestinal mucosa was severely fibrous and necrotic in large areas, and shedding. The liver is brown with white necrotic spots.

Fatty liver : The state of hepatic steatosis, or fatty liver, reflects the accumulation of lipids in the liver. Consequently, liver cells are reducing in efficiency, and they might even be destroyed and replaced by connective tissue. It is a non-infectious metabolic disorder, resulting in liver rupture, hemorrhage, reduced egg production, increased FCR, reduced eggshell quality, internal bleeding and higher mortality rates. Fatty livers are often seen in laying hens that are fed with layer diets with an imbalance between energy and protein. The excess of energy intake whilst limited activity contributes to the development of fatty livers. The fatty liver cause production drop and mortality dueto rupture of liver and mortality.

Fat digestion results in less stress on the liver compared to the digestion of carbohydrates. Replacing part of the carbohydrates by fat, while not increasing the energy level, helps to prevent a fatty liver.

Diets should contain enough amounts of lipotropic factors, like choline, methionine and B12. Lipotropic nutrients stimulate fat export from the liver and consequently can support fatty liver recovery. Dietary choline is fluctuating in level and bioavailability among the different raw materials. It is advised to have 500 ppm choline during the rearing period, and 1000 ppm choline during the egg production period.

Sufficient levels of antioxidants, like vitamin E and Selenium prevent oxidative rancidity of the fatty liver and consequently cell damage. During the egg production period it is recommended to feed 0.3 ppm Selenium and 50 ppm vitamin E.

Keeping the liver healthy with certain nutrients and phytogenics

Vitamin E to enhance general liver health

Vitamin E is one of the most potent antioxidants in nature. It plays a key role in neutralizing free radicals or reactive oxygen species (ROS).

The biological activity of vitamin E is not limited to its antioxidant properties: it is involved in the regulation of the following processes: inflammatory response, gene expression, certain enzymes, cellular signaling, and cell proliferation. Vitamin E is protective against substances that are toxic to the liver and provides antioxidant and cytoprotective activity to hepatocytes.

During fatty liver disease, the administration of vitamin E reduces the deposits of fats in the hepatocytes, ameliorates inflammation and fibrosis and activates certain beneficial metabolic processes in the liver.

 Selenium and zinc

 Birds with zinc and/or selenium deficiencies are more susceptible to fatty liver disease.

On the other hand, the administration of zinc and selenium helps to prevent the onset of the hepatic steatosis and to reduce the damaging effects once the animals are already affected by the disease.

Essential oils and other phytogenics that enhance liver function

 Certain essential oils, plant extracts and purified compounds of plant origin have liver-protective activity, through several possible mechanisms of action:

• Show antioxidant activity, promoting the natural antioxidant metabolic pathways of the liver and preventing oxidation of lipids.
• Facilitate the elimination of toxins and other harmful substances out from kidney and liver, which is very useful in long live birds because they are frequently exposed to mycotoxins, pharmaceutical products, heavy metals, dioxins and other toxins.
• Reduce the accumulation of fats in the hepatocytes.
• Stimulate the secretion of bile, improving feed digestion.
• Possess antinflammatory activity
• Prevent the death of the hepatocytes

 Liver tonic benefits:

It is advisable to provide liver tonics containing the above components,
which improves overall liver function . Protects the liver from the effects of toxins in poultry. Enhances growth, productivity, and efficiency. Overall growth and development of poultry. Aids in recovery following medication and other periods of stress such as introduction of new birds, molt, disease challenge and heat stress. Supplements your poultry’s nutritional requirements.

How many days the liver tonic is to be  given to chicken?

Growers / Layers 20 ml per 100 birds through drinking water as a week a month program. Broilers 5-10 ml daily per 100 birds through drinking water from 2nd to 6th week.

Conclusion

A healthy liver is key in order to maintain the production of first quality eggs during an extended laying cycle. A fatty liver will result in a reduced production of egg yolk, consequently less eggs and lower egg mass will be produced. Furthermore, the activation of vitamin D3 is impaired, which affects the calcium metabolism and consequently eggshell quality and so the number of first quality eggs. In order to prevent the laying hens from developing a fatty liver, make sure you proper monitor the flocks body weight and feed intake. Further, provide a well-balanced diet, including enough lipotropic factors as given in this article.

( Author acknowledge the  google for images and References)

(*Former and Founder VC,KVAFSU, Bidar. former Director IAH&VB< Bangalore, Former Prof and University head, Dept. of pathology, Veterinary College UAS Bangalore)