The liver is the central laboratory of a chicken’s body. It is essential that this organ is kept in an excellent condition in order to maintain a healthy bird. Understanding the metabolic function and causes of disruptions in liver functions helps us to provide the birds with the right feed and health treatment.
After dissection, the first organ revealed is the liver.
When we cut open the body of a chicken, the first organ that is most likely revealed is the liver. The message is clear. Nature wants us to examine the liver carefully before proceeding to the other organs. The liver contains great functional reserve capacity, which is very important in domestic animals subjected to high production requirements. This organ adapts easily to different conditions by increasing the intensity of its functions. Particularly in broilers, the liver has to cope with many challenges, including high energy level feed, the addition of chemotherapeutics, coccidiostats and others, whose desired metabolites must be maintained in equilibrium by hepatic homeostasis. Incidental treatments with highly hepatotoxic and nephrotoxic antibiotics or sulfonamides pose serious risks and cause situations of difficult prognosis during a 40-45 day period in which the body acquires satisfactory muscular mass. What is the function of the liver and what might be the cause of malfunctioning?
Functions of the liver
The liver in a chicken has several significant functions, including bile secretion, metabolism of carbohydrates, lipids and proteins, as well as several other metabolic functions.
The liver produces yellowish-green fluid called ‘bile’. This fluid is stored in the gall bladder and passed through ducts to the small intestine where it plays an essential role in emulsifying fats. The amount of bile secreted depends upon many factors, including the blood flow from the liver, the composition of ingested food, and hepatic circulation of bile salts. Bile aids in the absorption of fats due to its emulsifying activity and activating effect on pancreatic lipase, and also the digestion of carbohydrates due to the presence of amylase. Bile salts have two important activities in the digestive tract.
1. They have a detergent effect on the fatty particles of food causing the subsequent decrease of agitation in the intestine. This allows fat globules to disintegrate into very small particles.
2. They aid the absorption of fatty acids and monoglycerides from the intestine. This process is called hydrotropic function. When fat is not properly absorbed, fat soluable vitamins are also not absorbed. Although the body may contain adequate deposits of vitamins A, D and E, the lack of vitamin K deposits may results in the development of vitamin K deficiency after bile secretion has stopped. This, in turn, prevents the liver from producing a sufficient amount of factor VII and prothorombin, which causes blood coagulation disorder. Bile also contains bicarbonate and chloride. When the volume of bile secretion increases, chloride concentration decreases and bicarbonate concentration increases, thereby producing a higher pH.
Metabolism of carbohydrates:
The main function of all ingested carbohydrates is to provide energy immediately required by the host. The monosaccharides coming from the intestine to the liver (fructose and galactose) are transformed into glucose, which can undergo three processes.
a. It can be stored as glycogen in the liver and muscles
b. It can be oxidised in the tissues to become CO2 and H2O.
c. It can be converted into fat and stored in fatty deposits.
The liver is the most important organ for the regulation of glycemia. It makes glucose from carbohydrate or non-carbohydrate elements and the occurring glyconeogenesis transforms the glucose, fructose and galactose absorbed in the intestine into glycogen,which is then stored. When glycemia levels decrease, the liver turns glycogen into glucose and also makes glucose
out of non-carbohydrate sources, particularly certain amino acids. When glycemia levels increase, the liver transforms glucose into glycogen and a small amount of fatty acids. This regulation process is called hepatic homeostasis.
Metabolism of lipids:
The liver is, more than any other organ, actively involved in the metabolism of lipids. Its main functions include:
a. Synthesis of fatty acids from carbohydrates and certain amino acids, and cholesterol from acetylcoenzyme A, plasma lipoproteins and ketone bodies.
b. Degradation of fatty acids derived from deposited and dietary triglycerides in order to meet energy requirements.
c. Removal of phospholipids and free and esterised cholesterol from the blood.
d. Lengthening and shortening the chain of fatty acids.
e. Saturation and unsaturation of fatty acids.
f. Controlling the storage of hepatic and deposited fats.
Metabolism of proteins:
The dietary proteins are digested through the action of hydrolytic enzymes (protease), which break down the peptide bonds and release amino acids. These are absorbed by the intestinal cells and passed into the portal vein. They then enter the liver and are transported via systemic circulation to other tissues and organs. The liver helps the protein metabolism by deamination of amino acids and the formation of urea for ammonia suppression in bodily fluids.
Other functions of the liver: The liver also has several other metabolic functions
a. Storage of iron: most of the iron in the liver is stored as ferritin.
b. Storage of vitamins: the liver is an excellent source of vitamins. Vitamin A is stored in higher amounts than others; it can also store great amounts of vitamins D & B12.
c. Blood coagulation: the liver produces many substances used in blood coagulation, including fibrinogen, prothombin, accelerated globulin,factors VII etc. Furthermore, the liver also stores vitamin B12, an anti-anaemic factor necessary for maturation of erythrocytes.
d. Conjugation and excretion of steroid hormones: practically all steroid hormones are at least partially conjugated in the liver and eliminated in the bile. When the liver is impaired, a great amount of these hormones often accumulate in the bodily fluid, producing symptoms of hormonal imbalances.
e. Detoxification: the liver transforms poisonous substances produced by the body into harmless metabolites by way of oxidation and conjugation. These metabolites are later easily excreted via the kidneys.
f. Maintenance of hormonal balance.
g. Helps the body resist infection.
h. Removal of ammonia from the blood.
Hepato protective herbs: Capparis spinosa, Chicorium intybus, Solanum nigram, Terminalia arjuna, Tamarix gallica, Glycyrrhiza glabra, Mentha piperata, Glycine soja.
Liver enzymes: Liver enzymes are proteins that help to speed up a chemical reaction in the liver. Under normal circumstances, these enzymes reside within the cells of the liver. But when the liver is injured, these enzymes are spilled into the blood. The enzymes produced in the liver are: aspertate ammino transeferage (AST), alanine amino transeferage (ALT), lactic dehydrogenage (LDH), glutamate dehydrogenage (GLDH) and alkaline phosphatage.
A complete liver tonic: The liver performs many complex functions to maintain homeostasis (harmony among all the systems of body). When the liver is affected due to any reason, efficiency of the liver comes down in detoxification and metabolic processes. This, in turn, affects the overall performance of the bird, whether it be a broiler, breeder or layer. The combination of lipotropic agents, liver stimulants, antioxidants, mould inhibitors and toxin binders can work as a complete liver tonic.
|Liver stimulants||Potentiating the liver function|
|Tricholine citrate||Mobilising fat from liver|
|Inositol||Mobilising fat from liver|
|Vit B12||DNA synthesis and rejuvenation of the liver|
|Biotin||Better utilisation of fats|
|Protein hydrolysate||Ready source of amino acids for hepatic regeneration|
|Methyl donors||Facilitate detoxification and liver cell rejuvenation|
|Vit E and selenium||Natural defence against free radicals causing cell damage, including that of the liver|
|Mould inhibitors and toxin binders (organic acids, HSCAS and MOS)||Minimises mycotoxin formation, adsorption, and protects vital organs.|