porcus - sappo

34
nutrition
Mycotoxins Continued from p 33
intoxication with T-2 toxin may be a consequence
of shock syndrome with reduced
cardiac output and hypotension.
Similar to DON, Type A trichothecenes
can also reduce feed intake via altered
brain neurochemistry.
Swine fed 5 to 10 ppm T-2 toxin displayed
reduced feed intake and weight
gain while complete feed refusal was
observed at 16 ppm. Growing swine
fed T-2 toxin became soporific and
developed dermatitis and crusting of the
skin on the snout, nose, oral commissure,
ears and prepuce. Gastrointestinal
hemorrhagic syndrome has been associated
with natural trichothecenes feed
contamination in beef cattle and swine.
The specific T-2
toxin induced oral lesions serve as an
indicator of possible diet contamination
with Fusarium toxins. Trichothecene A
mycotoxins-induced immune suppression
affects all the components of the
immune system (inflammation, humoral
and cell-mediated responses).
Feeding swine 0.5 to 3 ppm T-2 toxin
for 21 days reduced specific antibody
levels to horse globulin and peripheral
blood mononuclear cells stimulation.
Type B trichothecene Fusarium
mycotoxins
The major mycotoxin belonging to this
group is DON and it is generally considered
as a marker for the presence of
other Fusarium mycotoxins. Pig is the
most sensitive domestic animal species
to DON and DON-induced feed refusal
and the subsequent growth depression
has been causing major economic
losses globally.
The effect of DON in reducing feed intake
has been related to elevated blood
tryptophan and brain serotonin concentrations.
DON is usually accompanied by
fusaric acid as a co-contaminant and the
loss of appetite is greater when they are
present together.
Pair-feeding studies in pigs have
shown that feed refusal can explain
most of the growth depression observed
in pigs exposed to DON. When fed at
low levels, however, pigs can consume
DON-contaminated feed and may be
exposed to its direct immunosuppressive
effects.
Monocytes, macrophages, as well as
T- and B-lymphocytes of the immune
system can be cellular targets of DON
and other trichothecenes. A great deal of
research has been conducted on DON-
induced IgA nephropathy in mice and
elevated serum IgA concentrations have
been noted in pigs. Feeding of up to 4.7
ppm DON for nine weeks to growing
pigs resulted in dose-dependent reduction
in secondary antibody response to
tetanus toxoid. Feeding DON-contaminated
grains can increase the incidence
of stillborn piglets in gilts. Sows fed the
same contaminated grains exhibited
reduced feed intake, weight loss, lower
serum protein and urea concentrations,
and tendency for increased weaning to
oestrus interval.
Fumonisins
Six different fumonisins (A 1 , A 2 , B 1 , B 2 ,
B 3 and B 4 ) so far have been isolated and
their mechanism of action appears to
be a disruption of sphingolipids synthesis
in biological membranes. Although
fumonisins toxicity in swine is characterised
by pulmonary oedema, their effects
on swine immunity seem to be of major
commercial significance.
In spite of discrepancy in the literature
related to the concentration of fumonisins
required to cause chronic toxicity in
pigs, Rotter and others (1996) showed
11% decrease in weight gain when
10 000 ppb FB 1 was fed to starter pigs.
It is important to note that this level of
fumonisin or even higher is very common
in swine feeds as in some countries
(such as USA) more than 50% of swine
diets may contain corn.
Bouhet and Oswald (2007) recently
reviewed the impact of fumonisin ingestion
on the intestine. Fumonisins can
alter intestinal epithelial cell viability and
proliferation, modify cytokine production,
and modulate intestinal physical
barrier function. All these effects may
lead to reduced nutrient absorption
and/or increased disease susceptibility.
Research from del Rio Garcia and others
(2007) also concluded that the combination
of aflatoxins and fumonisins at low
concentrations can produce synergistic
effects on altering the intestinal cellular
morphophysiology. FB 1 can also alter the
cytokine profile and decrease the specific
antibody response to vaccines.
Zearalenone
This is a very common Fusarium fungal
metabolite and often found in association
with either DON or nivalenol. Pigs
are very sensitive to zearalenoneinduced
oestrogenic syndrome which is characterised
by reddening and increased size
of vulva, increased size of mammary tissue,
abnormal lactation, infertility, pseu-
dopregnancy, still births, abortions and
rectal or vaginal prolapses. It has been
recommended that 0.5 ppm zearalenone
would have no serious effects on the
reproductive efficiency of young gilts.
This recommendation, however, needs a
revisit as more information is now available
on the previously described masked
zearalenone. Unlike the reproductive
function, growth performance in pigs is
less affected by zearalenone and further
research is needed to define its impact
of on the immune system.
Ergot alkaloids
Ergotism is the disease caused by the
ingestion of alkaloids contained in the
sclerotia of Claviceps species. There are
several ergot alkaloids detected in
grains (sorghum, wheat, barley, oat and
rye) used for swine feed and these
are pharmacologically active compounds.
The effect of feeding ergotcontaminated
grain to pigs is not consistent,
and ultimately depends on both the
ergot content and the alkaloid concentration.
Murphy (2006) suggested that the
maximum tolerable ergot level in the diet
was 0.10 and 0.05% based on average
daily gain and average daily feed intake,
respectively, corresponding to 2.07 mg
and 1.04 mg alkaloid/kg diet. Increased
intake of ergot-contaminated feed can
cause a severe reduction in the growth
performance of weaned pigs with or
without an effect on feed intake.
Ergot alkaloids can affect the reproduction
of sows through the effects on
prolactin levels. Because of the wide biological
variation in both the quantity and
quality of the alkaloids present in ergot
sclerotia, it is very difficult to establish
safe levels.
Mycotoxin interactions in pigs
Mycotoxins seldom occur in isolation
in poultry feeds. Mycotoxins discussed
above and many more occur together
and by no means do the mycotoxins
discussed above form a complete list.
This co-occurrence makes the individual
mycotoxin tolerance dose irrelevant (safe
levels) and therefore, the mere presence
of multiple mycotoxins in swine feed
should be considered as a warrant.
Mycotoxin interactions within the body
of pigs are very well proven. These interactions
are mainly additive in nature, but
can be synergistic antagonistic as well. It
is important to note that the type of interaction
can vary for different parameters
in the same animals.
Porcus Januarie/Februarie 2012