Farm Animal Metabolism and Nutrition

produced by certain strains of Aspergillus
flavus and A. parasiticus (Smith, 1997).
The aflatoxins are a group of structurally
related fluorescent heterocyclic compounds
characterized by dihydrofuran or tetra-
hydrofuran residues fused to a substituted
coumarin moiety. This group comprises
aflatoxin B 1 , B 2 , G 1 and G 2 (designated
AFB 1 , AFB 2 , AFG 1 and AFG 2 , respectively).
In addition, aflatoxin M 1 has been identi-
fied in the milk of dairy cows consuming
AFB 1 -contaminated feeds. The aflatoxigenic
Aspergilli are generally regarded as storage
fungi, proliferating under conditions of
relatively high moisture/humidity and tem-
perature. Aflatoxin contamination is, there-
fore, almost exclusively confined to tropical
feeds such as oilseed by-products derived
from groundnuts (Arachis hypogaea),
cottonseed and palm kernel. Aflatoxin
contamination of maize is also a significant
issue in warm humid regions where A.
flavus may infect the crop prior to harvest
and remain viable during storage.

Ochratoxins

Another species of Aspergillus (A.
ochraceus) produces a different group of

mycotoxins, represented by the ochratoxins,

a property it shares with at least two

species of Penicillium (Abramson, 1997).

The ochratoxins are a family of structurally

related compounds based on an iso-

coumarin molecule linked to phenylala-

nine. Ochratoxin A (OA) and ochratoxin B

are the only two forms to occur naturally as

contaminants, with OA being the more

ubiquitous, occurring predominantly in

temperate cereals and in the tissues of

animals fed on these grains.

Fusariummycotoxins

Extensive data now exist to indicate the

global scale of contamination of cereal

grains and animal feed with Fusarium

mycotoxins (D’Mello et al., 1997). Of parti-

cular importance are the trichothecenes,

zearalenone (ZEN) and the fumonisins. The

trichothecenes are subdivided into four

basic groups, with types A and B represent-

ing the most important members. Type A

trichothecenes include T-2 toxin, HT-2

toxin, neosolaniol and diacetoxyscirpenol

(DAS). Type B trichothecenes include

deoxynivalenol (DON, also known as vomi-

toxin), nivalenol and fusarenon-X. All

Anti-nutritional Factors and Mycotoxins 387

Table 18.2.Toxigenic species of fungi and their principal mycotoxins.

Fungal species Mycotoxins

Aspergillus flavus; A. parasiticus Aflatoxins
A. flavus Cyclopiazonic acid
A. ochraceus; Penicillium viridicatum; P. cyclopium Ochratoxin A
P. citrinum;P. expansum Citrinin
P. expansum Patulin
P. citreo-viride Citreoviridin
Fusarium culmorum;F. graminearum Deoxynivalenol
F. sporotrichioides; F. poae T-2 toxin
F. sporotrichioides; F. poae Diacetoxyscirpenol
F. culmorum; F. graminearum; F. sporotrichioides Zearalenone
F. moniliforme Fumonisins; moniliformin; fusaric acid
Alternaria alternata Tenuazonic acid; alternariol; alternariol methyl
ether; altenuene
Acremonium coenophialum Ergopeptine alkaloids
A. lolii Lolitrem alkaloids
Claviceps purpurea Ergot alkaloids
Phomopsis leptostromiformis Phomopsins
Pithomyces chartarum Sporidesmin A