Agriculture Reference
In-Depth Information
examination, the carcases should be condemned as the
cause, other than pathophysiological, might be mycotox-
ins or polychlorinated biphenyl compounds containing
dioxin. Liver damage may be the result of congestion of
aflatoxin, coal tar products or toxins derived from plants
such as cortalaria or rapeseed.
In broiler chickens in the United States and the United
Kingdom, cholangiohepatitis (possibly caused by
Clostridium perfringens
or secondary to viral infection in
the biliary system) is the most common cause of liver
damage which results in ascites. In both meat-type ducks
and breeders, amyloidosis of the liver frequently causes
ascites. Feed regimes which restrict the early growth of
broilers have had a significant effect in decreasing the
incidence of ascites.
Carcase appearance defects include red wing tips, red
pygostyles, red feather tracts, engorged wing veins,
haemorrhagic wing veins and haemorrhage in shoul-
ders. Haemorrhages may occur in the muscles of the leg
and breast, and broken bones include the furculum,
coracoid and scapula. Unless severe, only local condem-
nation is required.
Fractures, without bruising, have been caused in the
processing after bleeding and are due to defects in pro-
cessing. It may require resetting of the machinery.
Breast blisters and hock burn
These are caused when a part of the bird comes into
contact with damp litter, which causes breast blisters
and hock burn. These occur more often in birds with
leg weakness and may become infected, and this will
require more extensive trimming. The hock burns are
unsightly and in some processing plants are mechani-
cally removed. The presence of hock burns, in some
companies, affects the quality assessment of the bird
and therefore the price. Attention to litter management,
ensuring adequate ventilation, the avoidance of water
spilling from the drinkers and good healthy birds will
prevent these conditions.
Rupture of the gastrocnemius tendon.
This occurs
when the tendon is unable to support the bird's weight
and may be followed by a greening around the area above
the hock. Birds being grown to heavier than normal
weights, for example, for the Christmas or Easter market,
are particularly susceptible. Decreasing energy and pro-
tein levels in the earlier stages of growth helps prevent
this condition. At times, infective organisms such as
staphylococci and/or viruses may be responsible.
Judgement.
Condemnation of the affected part;
should the bird be emaciated, whole carcases
condemnation.
Slaughter liver or cholangiohepatitis
This is a condition of enlarged livers. Histologically,
there is a severe, chronic hepatitis in which bile duct pro-
liferation is a striking feature. It affects all of the liver.
This may be accompanied by other changes.
Judgement.
Depends on other lesions and condition
of carcase.
Fatty liver haemorrhagic syndrome (FLHS)
The liver is very enlarged, pale and friable owing to the
large amount of fat. There is also increased abdominal
fat deposition. It may be due to nutritional imbalances,
high temperatures, reduced exercise and strain of bird. It
is a disease, predominantly, of older laying birds.
Vices
Vices in poultry may be considered to be undesirable
behaviour, usually precipitated by some aspects of man-
agement or environment. Once started by individuals, a
vice tends to be copied by other birds, and the resulting
injuries can often lead to death or downgrading of
carcases.
Ascites
Ascites caused by right ventricular failure (RVF) has for
many years resulted in significant mortality in broiler
chicks raised at high altitude. There has been a dramatic
increase in other areas which coincides with a continu-
ing genetic and nutritional improvement in feed effi-
ciency and rate of growth. This rapid growth requires high
levels of oxygen which are not available and, combined
with restricted space for blood flow through the capillar-
ies of the lungs, leads to ascites and death. Right ven-
tricular hypertrophy is a response to the increased
workload, and this eventually leads to RVF if the volume
or pressure load persists (Fig. 10.23).
Most cases of ascites occur as sudden death on the
farm, but should any be found on post-mortem
Cannibalism
Outbreaks sometimes occur without any obvious cause.
Predisposing environmental conditions include exces-
sive light in pens and cages, boredom and vent pecking,
insufficient feeding and drinking space, high-density
stocking and too much heat during brooding. Blood is
found around the vent, through which much of the intes-
tine may have been removed by the cannibalising birds.
Feather pecking or pulling
This is sometimes precipitated by nutritional deficien-
cies but may also be started by the bullying of a weak or
sick bird. Overcrowding as broilers and turkeys reach
slaughter age may be followed by an outbreak of feather
