Farm Animal Metabolism and Nutrition

health, the carcinogenic potential of myco-
toxins is perceived to be more important
than their respective LD 50 values.

Chronic effects

A number of ANFs and mycotoxins are
associated with well-defined syndromes
identified from field cases of toxicity
(Tables 18.3 and 18.4). Thus the aetiology
of ‘clover disease’ in sheep has been linked
with the intake of phyto-oestrogens, while
in the case of DON, the effects on feed
refusal and emesis in pigs are now con-
sidered to be characteristic for this
Fusarium mycotoxin.
It is not intended to review all aspects
of the chronic toxicity of the ANFs and

mycotoxins described above. A more

salutary approach entails a comparison of

these two groups of compounds with a

view to discerning common features in

their primary effects on farm animals.

Digestive dysfunction and

nutrient malabsorption

Many ANFs modulate digestive function

and nutrient metabolism, but there is

increasing evidence that some mycotoxins

may act in a similar manner. The classical

view of lectins is that they exert their

deleterious effects via reduced nutrient

absorption following extensive structural

and functional disruption of the intestinal

microvilli (D’Mello, 1995). Thus, con-

canavalin A enhances shedding of brush-

border membranes and decreases villus

390 J.P.F. D’Mello

Table 18.3.Adverse effects of proteins and secondary substances from plants.

Plant components Adverse effects

Lectins Intestinal lesions
Reduced nutrient absorption
Proteinase inhibitors Reduced protein digestion
Endogenous loss of amino acids
Antigenic proteins Intestinal lesions
Diarrhoea
Immune hypersensitivity
Condensed tannins Impaired rumen function
Reduced liveweight gain and wool growth
Quinolizidine alkaloids Reduced feed intake
Teratogenic effects
Glucosinolates Organ damage
Goitrogenic effects
Reduced feed intake
Amino acids
S-methylcysteine sulphoxide Haemolytic anaemia
Organ damage
Mimosine Shedding of fleece
Reduced appetite
Organ damage
Death
Phyto-oestrogens Reproductive dysfunction
Steroidal saponins Hepatogenous photosensitization
Vasoactive lipids Late-term abortion in cattle
Gossypol Organ damage
Cardiac failure
Death
Cyanogens Inhibition of cytochrome oxidase
Central nervous system dysfunction
Respiratory failure
Cardiac arrest