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.

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WORLD POULTRY - Vol. 23 No 10. 2007 www.WorldPoultry.net 34
The liver: a big organ with a
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.
By Dr Avinash Dhawale, Nagpur, India
W
hen 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.
Bile Secretion: The liver produces a
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
aids 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
After dissection, the first organ
revealed is the liver.
A normal liver. A mild case of Fatty Liver Haemorrhagic
Syndrome (FLHS). Note the yellow colora-
tion brittleness of the liver.
.
A moderate case of FLHS.

2. WORLD POULTRY - Vol. 23 No 10. 2007 www.WorldPoultry.net 35
big role
increases, thereby producing a higher
pH. The bile, on entering the duodenum,
then helps neutralise the acid chyme
of the stomach.
Metabolism of carbohydrates: The
main function of all ingested carbohy-
drates is to provide energy immediately
required by the host. The mono-
saccharides 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 H2
O.
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 acetyl
coenzyme A, plasma lipoproteins
and ketone bodies.
b. Degradation of fatty acids derived
from deposited and dietary tri-
glycerides 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
An extreme case of FLHS.
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.
Ingredient Function
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 Minimises mycotoxin formation, adsorption, and protects
(organic acids, HSCAS and MOS) vital organs

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WORLD POULTRY - Vol. 23 No 10. 2007 www.WorldPoultry.net 36
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.
Liver diseases
The liver is one of the most important
organs for maintaining the internal
environment of the body. However,
important damage can occur before
clinical signs become apparent. The
clinical silence of the hepatic lesions is
due its significant reserve of functional
capacity, its complex and multiple
function capacity, and its extraordinary
capacity for regeneration. In the
literature we recognise several syndromes,
of which not all have been well
documented in birds. One of them is
hepatoencephalopathy. This is not a
disease in itself, but a medical condition
characterised by neurologic symptoms
caused by intoxication of the brain by
products of protein digestion, namely
ammonia. A tentative diagnosis of
hepatoencephalopathy is often made
when neurologic signs are seen in
birds with liver disease.
Hemochromatosis is another liver
syndrome of which we know little
about. It is a disease of excessive
storage of hemosiderin (hemosiderosis)
in various body tissues. Hemosiderin
is an iron-containing pigment derived
from hemoglobin. The principle site
of iron accumulation is the liver.
The aetiology at present is unknown,
but a high dietary iron has been
suggested.
Fatty Liver Syndrome
Fatty Liver Haemorrhagic Syndrome
(FLHS) occurs primarily in birds kept
in cages, but has also been recognised
as a less significant problem in birds
kept on litter. It is associated with
birds fed high energy diets and is
most often seen during the summer
months.
The first sign of the syndrome is an
increase in mortality of the flock with
birds in full production being found
dead with pale heads. Mortality usually
does not reach 50%, but there is often
a sudden drop in production. Hens
may be overweight with large pale
combs and wattles. Dead birds have
large blood clots in the abdomen arising
from the liver. The liver is generally
enlarged, pale and friable. Large
amounts of fat are present in the
abdominal cavity and around the
viscera. Most of the birds have active
ovaries and often have an egg in the
oviduct. The suffering birds have an
increased concentration of AST, LDH,
GLDH, estadiol, calcium and phos-
phorus in the plasma compared to
the unaffected birds.
The cause and origin of the disease
is associated with high laying intensity,
excess energy, high energy/protein
ratio, energy source (sub-clinical FLHS
is more present in corn-based diets
than in wheat-based diets), low level
of dietary calcium, protein source
(FLHS incidence is more present in
soya-based diets than in fish-based
diets), deficiency of lipotropic compounds
(choline, methionine etc. and vitamins,
such as vitamin C and E and minerals
like zinc, copper, iron and manganese),
stress (this induces liberation of
corticosteroides which enhances
lipogenesis and leads to FLHS),
temperature (high temperature
leads to increased hepatic fatty acid
synthesis) and mycotoxins.
Treatment
The incidence of FLHS can be reduced
by restricting energy intake either by
feed restriction or by lowering the
metabolisable energy content of the
diet. The carbohydrate content of feed
is decreased by increasing the amount
of fat, which is rich in linoleic acid.
Extra lipotropes like lecithin, choline,
inositol, betaine and methionine also
contribute to a healthy liver as do
vitamins like B1
and biotin, which play
an essential role in the metabolism of
carbohydrates. Vitamin E in combina-
tion with selenium has a positive effect
on the synthesis and transport of fats.
Impact of fatty liver on antibiotics
In a study, the concentrations of five
antibiotics were determined in chicken
serum before and after they were
induced into fatty liver. The measured
peak concentrations were higher for
lincomycin (LMC) and erythromycin
(ERM) and lower for penicillin (PCL)
and oxytetracyclin (OTC), while strepto-
mycin (SMC) remained unchanged.
The peak concentration of streptomycin
appeared earlier and the peak of OTC
later than in the normal chickens. The
eliminated half lives were shorter for
ERM, LMC and SMC and increased for
PCL and OTC. It is clear from this study
that the efficacy of some antibiotics is
altered in FLHS.
Bile acids as an indicator of
Hepatobiliary disease
Plasma bile acids (BA) and there salts
are formed in the liver from cholesterol
and are excreted in the intestine where
they assist in the digestion of fats. Via
the enterohepatic circulation, over 90%
bile is reabsorbed in the jejunum and
ileum. Plasma BA concentrations
including their salts and corresponding
glycine and taurine conjugates (BA) are
a reflection of the clearing capacity for
bile acids of the liver. All liver functions
(such as extraction, conjugation and
excretion) are involved in this process,
and the BA provides information on the
combined effects of these functions. It
is now known that BA is a sensitive
constituent for evaluating liver function
and is widely used in man and domestic
animals, including birds. In experimental
liver disease, a 5-10 fold increase of BA
over the upper limit of the reference
range is common.
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.
Of these five, the first three are
produced in the cytoplasm while the
fourth and fifth are produced in the
mitochondrion and the membrane
respectively.
Generally, increased enzyme concen-
trations are a measure of recent organ
damage rather than decreased organ
function. Cytoplasmic enzymes will be
released early in the cell degeneration,
while mitochondreal enzymes are
released after advanced cell damage.
Increased plasma GLDH activities are
associated with large necrotic areas in
the liver.
Summary
The liver performs a number of
metabolic functions in the body.
Since this organ receives almost all
the substance absorbed from the
small intestine, it always needs to
be maintained in the state of ‘rocket
engine’. Avoidance of excess fats and
mycotoxicosis shall always receive
top priority because the resultant
impaired fat metabolism could lead
to serious economic losses. Certain
nutritional alterations with the use
of HSCAS and MOS help protect
the liver - undoubtedly the central
laboratory of a chicken’s body. ■
Hepato-protective herbs
1) Capparis spinosa
2) Chicorium intybus
3) Solanum nigrum
4) Terminalia arjuna
5) Cssia occidentalis
6) Achillea millofolium
7) Tamarix gallica
8) Cynarascolymus
8) Escholtzia californica
9) Matricaria chamomilla
10) Taraxacum
11) Glycyrrhiza glabra
12) Grfloa frpndosa
13) Mentha piperata
14) Rosemarinus officinalis
15) Glycine soja