length, thereby reducing surface area for
absorption in the small intestine. With
other lectins, the lamina propria of the
intestine may become infiltrated with
eosinophils and lymphocytes. Although
the proteinase inhibitors depress proteolysis
in the digestive tract, the adverse effects on
growth are thought to occur via more
complex mechanisms. It is envisaged that
inactivation of trypsin elicits the release of
cholecystokinin which stimulates pancreatic
production of digestive enzymes, including
trypsin and chymotrypsin. The net effect is
the loss of endogenous protein rich in the
sulphur-containing amino acids. It is this
depletion of critical amino acids which
reduces growth. A concomitant enlarge-
ment of the pancreas may also occur,
particularly in broiler chickens (D’Mello,
1995).
One of the most striking effects on
intestinal morphology and function occurs
on feeding soybean antigens to sensitized
mammals (D’Mello, 1991b). There is a
marked degree of uniformity in these
lesions, irrespective of animal species or of
the source of the antigenic protein.
Detailed analysis of the morphological
aberrations show that while normal villi
appear long and slender with tall columnar
epithelial cells, those of sensitized calves
and piglets are substantially shorter and
broader with some evidence of disorganized
enterocyte architecture. A consistent feature
accompanying these changes is the marked
increase in crypt depth following antigen
stimulation in both calves and piglets. Villi
from sensitized animals are distinguished
by prominent infiltration with lymphocytes
which may extend into the lamina propria.Anti-nutritional Factors and Mycotoxins 391Table 18.4.Deleterious effects of mycotoxins in animals.
Mycotoxins Deleterious effects
Aflatoxin B 1 Acute toxicity: LD 50 values, 1–17.9 mg kg^1 BW (laboratory animals), 0.5 mg
kg^1 BW (ducklings); hepatic lesions; teratogenic.
Reduced feed efficiency, immune function and reproductive performance in
ruminants
Aflatoxin M 1 Hepatotoxic
Ochratoxin A LD 50 <6 mg kg^1 BW (pigs); implicated in porcine nephropathy; teratogenic;
carcinogenic to mice and rats
Deoxynivalenol LD 50 70 mg kg^1 (mice); potent feed intake inhibitor in pigs; causes erosion of
gastric mucosa; affects feed choice in mink; teratogenic; immunosuppressive.
Ruminants tolerant
Diacetoxyscirpenol LD 50 23 and 5 mg kg^1 BW, respectively (mice); mouth lesions in poultry; in
(DAS) and T-2 toxin sows T-2 toxin can cause infertility and abortion. Growth depression in broiler
chicks caused by DAS increased by high-fat diet.
Implicated in field cases of mycotoxicoses in ruminants
Zearalenone LD 50 range: 2–10 g kg^1 BW; causes vulvovaginitis in gilts and anoestrus in
cycling females; feminization in male pigs; reduced spermatogenesis; reduced
milk production and hyperoestrogenism in cows; infertility in sheep
Fumonisins Mortality in chicken embryos; onset of mortality in chickens aided by
moniliformin; hepatic lesions in pigs and cattle; porcine pulmonary oedema;
equine leukoencephalomalacia
Fusaric acid Suppresses cell-mediated immunity; interactions with fumonisins and
deoxynivalenol
Tenuazonic acid LD 50 values 125–225 mg kg^1 BW in mice
Ergopeptine alkaloids Reduced growth, reproductive performance and milk production in ruminants;
increased susceptibility to heat stress
Lolitrem alkaloids Neurological effects: incoordination, staggering, shaking of head and collapse
in ruminants
Phomopsins Lupinosis in sheep: ill-thrift, liver damage, jaundice, photosensitization and
death; reduced reproductive performance of ewes
Sporidesmin A Facial eczema in sheep: liver damage, urinary lesions, photosensitization