Semi-Arid Warm-Season Grass Yield and Nutritive Value in Argentina

Abstract

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 Pampean Region of Argentina. This study, conducted over 2 years, 1990 and 1991, compared the winter forage quality produced during the previous growing season for 4 warm-season grasses; switchgrass (Panicurn virgutum L. cv. Pathfinder), kleingrass (Panicurn colorutum L.), tetrachne (Tetruchne dregei New) and weeping lovegrass (Erugrostis 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 subsamples of forage were divided into leaf and stem fractions. Forage quality analyses included: crude protein (CP), in vitro dry matter digestibility @VDMD), effective rumen degradability (ED), neutral (NDF) and acid (ADF) detergent fiber and lignin. Tetruclzne dregei produced forage with a higher leafxtem 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 cows. Dry matter yield of tetrachne was lower than that of weeping lovegrass, but differences were only significant in 1990. Kleingrass generally was high in quality and dry matter yield, although it was the lowest in percentage of leaves of the 4 species evaluated. Switchgrass was the least productive; the nutritive value of its forage was low, comparable 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 higher than the stems. Tetruchne dregei, the best of the species evaluated in this study, is a very promising warm-season grass, which could provide nutritious forage for winter grazing systems in the semiarid Pampean Region of Argentina.

Seasonal Trends in Chemical Composition and Digestion ofDichanthium annulatum(Forssk.) Stapf

“…With exception of K and Na all minerals were higher (Pe0.05) in leaves than in stems (Table 3). This fact confirms previous reports that plant parts differ in mineral content (McBee and Miller, 1990;Stritzler et al, 1996).…”

In vivo Digestibility of Kleingrass from Fecal Nitrogen Excretion

“…6.7 kg in period I to IV, respectively) were grouped by weight, and then randomly assigned within weight group, to 3 feeding levels (treatments): 0.5 maintenance level (feeding level = Li; 5 rams), 1.0 maintenance level (feeding level = L2; 5 rams), and ad libitum, 1.5 the actual intake of 2 days previous to feeding (feeding level = L3; 7 rams). Maintenance level was estimated according to the energy requirements (AFRC 1993) of rams, and the in vitro DM digestibility of the forage (Stritzler et al 1996). All animals were dewormed 15 days before the beginning of the study and housed in individual pens under continuous light, with free access to water.…”

The seasonal and inter-annual patterns of biomass accumulation and crude protein in kleingrass (Panicum coloratum) in the semiarid Pampean region of Argentina

“…This species begins growing approximately four weeks after weeping lovegrass does, and it is known to have high forage accumulation (Stritzler et al, 1996) and nutritional quality (Ferri et al, 1998). Kleingrass began spreading in cattle systems 20 years ago (Petruzzi et al, 2003) because it is well adapted to the environment.…”