Focal Duodenal Necrosis (FDN)
in table egg flocks
By Eric Gingerich, DVM ACPV
Focal duodenal necrosis (FDN) is an intestinal disease of table egg ocks rst
described by Dr. Patricia Dunn of the
Diagnostic Laboratory at Pennsylvania State
University in a cage-free layer ock in 1997.
Since then, FDN has
been observed by
poultry health workers in most of the
states in the United
States. Layers of
all ages are susceptible but FDN has
not been observed
in pullets prior to
maturity. FDN has
Eric Gingerich, DVM
also been found in
ACPV
organic ocks.
Various names have been used to describe
the disease such as “gray gut”, “MUD”
(multifocal ulcerative duodenitis), and FND
which is the original acronym which is most
commonly used.
FDN impacts production goals
The condition is characteristically associated with an inability of a ock to attain standard egg weight or egg production
goals or a combination of these parameters.
Egg weight lags behind normal by up to two
pounds per case in young ocks. Peak egg
production may be 2% or 3% below standard
or ocks may show a post-peak drop of 1%
to 10%.
The only clinical sign reported is that
some of the birds show pale combs.
Financial loss depends on the severity of
the disease but will be at least 1 to 2 cents
per hen for each outbreak if only egg size
is affected for a three week period, and an
additional 3 cents per hen for each 1% drop
by nding FDN at the same incidence rate in
ocks irrespective of being fed these ingredients. The presence of tapeworms was also
Duodenal lesions indicate FDN
considered to be a factor but ocks both with
Diagnosis is based on observations made and without cestode infestation appear to be
when performing post mortem examinations equally affected.
of freshly euthanized birds. Necropsy of The cause of FDN is currently attributed
birds that have died naturally is not appropri- to the Gram positive bacterium Clostridium
ate as the duodenum, the site of FDN lesions, colinum which is responsible for ulcerative
decomposes quite rapidly after death. enteritis in quail and is frequently isolated
Active surveillance
for FDN is performed
in one major egg production operation by
sacri cing six birds
from ocks every two
weeks for necropsy to
ascertain the presence
of FDN lesions. The
duodenal loop is the
site of FDN lesions
which consist of single to multiple, dark,
irregularly shaped,
5- to 15-mm diameter
areas in the mucosa Duodenal loop of a hen affected with fdn showing darkened areas
that can be seen from
which are visible through the serosa.
the serosal surface.
Upon opening the
duodenum, the grey areas can be visualized
on the surface.
A “rotten-egg smell” due to the evolution
of hydrogen sul de from the lesions is noted
emanating from the surface of the intestine.
Histologically, a heterophilic in ltration of
the duodenal villus tips is observed with numerous bacteria visualized on the surface.
in egg production, assuming a depression of
three weeks in duration.
Cause not confirmed
Originally the condition was ascribed to
recycled feed ingredients such as bakery
waste, animal byproducts or certain sources
of calcium carbonate but this was disproved
from cases of necrotic enteritis in broilers
and breeders.
At this time the speci c cause has not been
con rmed as it is not possible to satisfy Koch’s
postulates by reproducing FDN with pure isolates of Cl. colinum. This nding is not unusual
for clostridial enteropathies which require predisposing nutritional, environmental, managemental or as yet non-de ned factors. The current theory is that the microenvironment of the
intestinal lumen may undergo changes which
lead to proliferation of Cl. colinum which
produces toxins. This may be stimulated by
suboptimal numbers of bene cial competitive
