Farm Animal Metabolism and Nutrition

number of the above compounds together
with others such as saponins, vasoactive
lipids, gossypol and cyanogens are
associated with anti-physiological and toxic
effects. It is generally accepted that the
diversity and severity of adverse effects of
ANFs are greater in tropical than in tem-
perate legumes (Kumar and D’Mello, 1995).
Studies are continuing on virtually all
aspects of the compounds listed in Table
18.1 and, as they do, newer concepts have
evolved. Thus the adverse effects of soy-
beans (Glycine max) have long been
associated with their content of proteinase
inhibitors (Norton, 1991). However, recent
data point to a significant role for antigenic
proteins in the aetiology of post-weaning
hypersensitivity reactions of piglets and
calves fed on diets based on heated
soybean products. Proteins with anti-
nutritional activity have been the subject of
considerable research at the fundamental
level and in feeding trials, particularly with
non- and pre-ruminant animals. Attention
has focused on the anti-nutritional proteins

of soybeans. However, these proteins, in

the form of lectins, proteinase inhibitors

and specific antigens, are widely distributed

and contribute significantly to the poor

nutritional value of seeds from diverse

tropical and temperate legume species

(D’Mello, 1995). The condensed tannins,

quinolizidine alkaloids, glucosinolates,

non-protein amino acids, phyto-oestrogens,

saponins and cyanogens are also ubiquitous,

occurring in both grain and forage plants.

Lectins

Lectins are proteins with a characteristic

affinity for certain sugar molecules or

glycoproteins present in the membranes of

different animal cells, including those of

the intestinal mucosa. Lectins also react by

this mechanism with red blood cells in

vitro, causing agglutination. This reaction

is used to recognize and detect lectins in

raw materials. The alternative term,

haemagglutinin, is thus often used to

384 J.P.F. D’Mello

Table 18.1.Diversity of anti-nutritional factors in plants.

Plant type Plant species Major anti-nutritional factors

Forage
Legumes Medicagospp. Phyto-oestrogens
Saponins
Trifoliumspp. Phyto-oestrogens
Lotusspp. Condensed tannins
Grasses Brachiaria decumbens Saponins
Panicumspp. Saponins
Cruciferae Brassicaspp. Glucosinolates
S-methylcysteine sulphoxide
Erucic acid
Browse
Legumes Acaciaspp. Condensed tannins
Cyanogens
Leucaena leucocephala Mimosine
Condensed tannins
Pine Pinus ponderosa Vasoactive lipids
Grain
Legumes Glycine max Proteinase inhibitors
Antigenic proteins
Lectins
Phyto-oestrogens
Saponins
Lupinusspp. Quinolizidine alkaloids
Saponins