R. Barahona et al., INTAKE, DIGESTION, AND NITROGEN-UTILIZATION BY SHEEP FED TROPICAL LEGUMES WITH CONTRASTING TANNIN CONCENTRATION AND ASTRINGENCY, Journal of animal science, 75(6), 1997, pp. 1633-1640
We conducted an experiment to determine the effects of concentration a
nd astringency of extractable and bound condensed tannins (CT) in trop
ical legumes on intake, digestibility, and nitrogen (N) utilization by
sheep. The test legumes (Desmodium ovalifolium and Flemingia macrophy
lla) had similar concentrations of extractable CT (90 g/kg DM) but dif
ferent concentrations of bound CT and astringency of tannins. Chopped,
sun-dried forage of each legume was sprayed with either water (contro
l) or polyethylene glycol (PEG, 35 g/kg of DM) to bind extractable CT
and fed daily (26 g/kg BW) to eight sheep with ruminal and duodenal ca
nnulas. The sheep also received starch-extracted cassava meal intrarum
inally (4 g/kg BW) as a constant source of readily fermentable carbohy
drates. Intake of the two legumes was not different (P > .05), but it
increased an average of 10% (P < .01) when extractable CT were reduced
from 90 to 50 g/kg of DM with PEG. Ruminal and total tract digestibil
ities of OM, NDF, and ADF were greater (P < .01) with D. ovalifolium t
han with F. macrophylla and increased for both legumes with the additi
on of PEG. Greater (P < .01) N flow to the duodenum, N absorbed from t
he intestine, and fecal N were observed with F. macrophylla than with
D. ovalifolium. Extraction of CT with PEG resulted in less (P < .05) r
uminal escape protein and less (P < .01) fecal N with both legumes, bu
t apparent postruminal N digestion was not affected. Changes in the co
ncentration of extractable CT in tropical legumes can significantly af
fect forage intake, digestion, and N utilization by sheep.