Farm Animal Metabolism and Nutrition

increased protein turnover. The overall
effect is a reduction in the efficiency of
utilization of absorbed arginine (D’Mello,
1995). AFB 1 can cause reduced feed
efficiency in ruminants (Table 18.4). This
may imply a reduced efficiency of utiliza-
tion of nutrients, but direct evidence is
lacking.

BENEFICIAL EFFECTS. Despite the evidence
presented in Table 18.5, CTs are generally
attributed with beneficial properties in
ruminant nutrition (Table 18.6). It is con-
sistently maintained that CTs may confer
protection from degradation of leaf proteins
in the rumen. Fraction 1 (F1) leaf protein
predominates in forage and its digestion in
the small intestine, as opposed to fermenta-
tion in the rumen, would be advantageous
to ruminants since F1 is of high biological
value, presumed to exceed that of microbial
protein. It has been suggested that a

complex is formed between CTs and F1

protein through reversible hydrogen bond-

ing which is stable at pH values between 4

and 7, but which readily dissociates on

either side of this range. Consequently, it is

envisaged that this complex escapes

fermentation in the rumen where the pH

ranges from 5 to 7, but dissociates on

exposure to gastric (pH 2.5–3.5) and

pancreatic (pH 8–9) secretions. The

obvious implication is that CTs protect

labile plant proteins in the rumen, thereby

increasing the supply of high-quality

protein in the duodenum. In terms of

individual amino acids, it has been shown

that Lotus pedunculatus, a tannin-contain-

ing legume, promoted a higher degree of

protection for cysteine, methionine and

phenylalanine than L. corniculatus, a

cultivar low in CTs.

Another attribute of CTs recently

proposed relates to amino acid utilization

Anti-nutritional Factors and Mycotoxins 393

Table 18.5.Anti-nutritional effects of condensed tannins present in legumes (adapted from Kumar and
D’Mello, 1995).

Legume Animal Anti-nutritional effect

Lotus corniculatus Steer Reduced DM digestibility in sacco, reduced VFA production in vitro
L. pedunculatus Sheep Inhibition of rumen carbohydrate digestion and reduced weight gain
Acacia aneura Sheep Reductions in: N digestibility, S absorption and wool yield
A. cyanophylla Sheep Negative N digestibility, reduced feed intake and body weight loss
A. nilotica (pods) Sheep Reductions in: N and NDF digestibility and growth
Calliandra calothyrsus Goat Reduced N digestibility in sacco
Prosopis cineraria Sheep Reductions in: digestibility of protein, iron absorption, feed intake
and wool growth. Weight loss
Lespedeza cuneata Sheep Reductions in: ADF, NDF, N and cellulose digestibility. Depressed
feed intake

Table 18.6.Putative benefits of secondary compounds of legumes in animal production.

Legume Beneficial properties Conditions/comments

Lotus pedunculatus Protein protection in the rumen 30–40 g of CTs kg^1 DM of legume
Cysteine, methionine and 50 g of CTs kg^1 DM of legume
phenylalanine protection in the
rumen
Bloat suppression 30–40 g of CTs kg^1 DM
L. corniculatus Increased utilization of cysteine 27 g of extractable CTs and 8 g of bound
for tissue synthetic reactions CTs kg^1 DM
Hedysarum coronarium Reduced gastrointestinal 100–120 g of CTs kg^1
parasitism in lambs
Acacia spp. Anti-protozoal properties Nature of compounds unknown