Ac. Longland et al., NONSTARCH POLYSACCHARIDE COMPOSITION AND IN-VITRO FERMENTABILITY OF TROPICAL FORAGE LEGUMES VARYING IN PHENOLIC CONTENT, Animal feed science and technology, 55(3-4), 1995, pp. 161-177
The fermentation kinetics of leaves of eleven tropical forage legumes
varying in phenolic and condensed tannin content were investigated. Th
e leaf samples were from Acacia cyanophylla, Chamaecytisus palmensis,
Calliandra sp., Dioclea guianensis, Flemingia macrophylla, Leucaena le
ucocephala, Sesbania sesban, S. goetzei and three accessions of Tadeha
gi sp. (accession numbers 13269, 13275 and 23227). The phenolic, conde
nsed tannin (bound condensed tannin and extractable condensed tannin)
and non-starch polysaccharide (NSP = to dietary fibre) contents of lea
ves were determined. Leaves were incubated at 39 degrees C with rumen
micro-organisms in a habitat-simulating medium and the fermentation ki
netics investigated using a pressure transducer. The NSP content of le
aves both pre-and post-incubation was quantified and proportional loss
es of the NSP constituents calculated. The NSP content of leaves range
d from 124-252 mg g(-1) dry matter, the major components in each case
being cellulose-derived glucose and the uronic acids. In all samples,
the most degradable NSP constituent was the uronic acids, closely foll
owed by arabinose; cellulose-derived glucose and xylose were the least
degradable NSP components. Samples ranked in terms of asymptotic gas-
pool in descending order as follows: L. leucocephala = C. palmensis >
D. guianensis > S. sesban > A. cyanophylla > S. goetzei > Tadehagi sp.
, (23227) > Tadehagi sp., (13269) > F. macrophylla > Calliandra sp. >
Tadehagi sp., (13275). There were significant relationships between ga
s accumulation throughout the incubation and the NSP loss (NSPL) value
s at the end of the incubation. Moreover, the gas pool at the end of t
he incubation period and NSPL were significantly correlated (r = 0.90)
with a yield constant (ml gas g(-1) NSP loss) of 200 ml. Furthermore,
there were significant (P less than or equal to 0.05) negative relati
onships between both gas accumulation and NSPL and the phenolic and co
ndensed tannin content of leaves.