Farm Animal Metabolism and Nutrition

Chapter 18

Anti-nutritional Factors and Mycotoxins

J.P.F. D’Mello

Biotechnology Department,

The Scottish Agricultural College, Edinburgh, UK

Introduction

The secondary metabolism of plants and
fungi results in the production of a diverse
array of compounds with the capacity to
induce anti-nutritional or toxic effects in
farm animals. In addition, some products
of primary metabolism of plants may also
be associated with adverse effects in these
animals. The term ‘anti-nutritional factor’
conventionally is reserved for those sub-
stances which reduce nutrient utilization or
feed intake in animals. In practice, a wider
definition is often adopted to include com-
pounds causing anti-physiological effects
such as impaired reproductive function or
reduced immunocompetence.Additionally,
manifestations of toxicity may accompany
these anti-nutritional and anti-physiological
effects. Furthermore, cereal plants, legumes
and grasses may become infected with fungi
during crop development or during storage
of harvested or processed grain. Many of
these fungi have the potential to synthesize
toxic secondary metabolites known as
mycotoxins. Although anti-nutritional
factors and mycotoxins conventionally are
considered to be distinct groups of
compounds by virtue of their different

biological origins, there are many parallel

features. Thus amino acids are common

precursors for certain compounds in both

groups. Furthermore, some anti-nutritional

factors (ANFs) share common chemistry

with mycotoxins, while other ANFs and

mycotoxins induce similar deleterious

responses in animals, precipitating effects

on rumen function, feed intake, reproduc-

tion and immunocompetence.

Anti-nutritional Factors

Table 18.1 provides a list of the major ANFs

which may occur in different plant species.

The table is not designed to be exhaustive

but illustrative of the diversity of com-

pounds with anti-nutritional activity. These

substances may be divided into two primary

categories: a heat-labile group, comprising

lectins, proteinase inhibitors and cyanogens

which are sensitive to standard processing

temperatures, and a heat-stable group

including, among many others, antigenic

proteins, condensed tannins, quinolizidine

alkaloids, glucosinolates, the non-protein

amino acids S-methylcysteine sulphoxide

and mimosine, and phyto-oestrogens. A

© CAB International2000. Farm Animal Metabolism and Nutrition

(ed. J.P.F. D’Mello) 383