The use of standing dead biomass, during the winter that was produced
by warm-season grasses in the previous growing season by pregnant beef
cows may be an alternative to grazing systems in the semi-arid Pampea
n Region of Argentina, This study, conducted over 2 years, 1990 and 19
91, compared the winter forage quality produced during the previous gr
owing season for 4 warm-season grasses; switchgrass (Panicum virgatum
L. cv. Pathfinder), kleingrass (Panicum coloratum L.), tetrachne (Tetr
achne dregei Nees) and weeping lovegrass (Eragrostis curvula (Schrad),
Nees cv. Tanganyka), Five harvests of the summer growth started after
the first frost, and were spaced evenly throughout the winter period,
Changes in the standing crop of dry matter were measured and subsampl
es of forage were divided into leaf and stem fractions, Forage quality
analyses included: crude protein (CP), in vitro dry matter digestibil
ity (IVDMD), effective rumen degradability (ED), neutral (NDF) and aci
d (ADF) detergent fiber and lignin, Tetrachne dregei produced forage w
ith a higher leaf:stem ratio and of generally higher quality, than the
other species, although the differences were not always significant,
Its CP content was marginally below the maintenance requirements of co
ws, Dry matter yield of tetrachne was lower than that of weeping loveg
rass, but differences were only significant in 1990, Kleingrass genera
lly was high in quality and dry matter yield, although it was the lowe
st in percentage of leaves of the 4 species evaluated, Switchgrass was
the least productive; the nutritive value of its forage was low, comp
arable or lower than that of weeping lovegrass, The first harvest date
was higher in nutritive value, Although the nutritive value of leaves
and stems were not compared statistically, the leaves tended to be hi
gher than the stems, Tetrachne dregei, the best of the species evaluat
ed in this study, is a very promising warm-season grass, which could p
rovide nutritious forage for winter grazing systems in the semiarid Pa
mpean Region of Argentina.