Winter grazing stockpiled native warm‐season grasses in the Southeastern United States

Abstract

In the Southeastern United States, native warm‐season grasses (NWSG) are not harvested during autumn to rebuild root reserves, resulting in de facto stockpiled winter forage. Senesced NWSG forage is considered nutritionally inadequate by temperate livestock managers, but comparable forage is regularly utilized in rangeland systems. This experiment compared the forage characteristics of two NWSG pastures: switchgrass [Panicum virgatum L. (SG)] and a two species mixture of big bluestem/indiangrass [Andropogon gerardii Vitman/Sorghastrum nutans L. (BBIG)] to tall fescue [Festuca arundinacea Schreb. (TF)]. During two winter periods (January‐April), monthly samples were collected and measured for dry‐matter herbage mass (HM), crude protein (CP), in‐vitro true dry‐matter digestibility (48 hr; IVTDMD), neutral detergent fibre (NDF), NDF digestibility (dNDF) and lignin. Across sampling dates, TF provided adequate forage for low‐input animal maintenance (90.3 CP g/kg; 488 g IVTDMD/kg; 4,040 kg DM/ha), while SG had lowest nutritive values and greatest DM (21.0 g CP/kg; 366 g IVTDMD/kg; 7,670 kg DM/ha). Samples of BBIG had results intermediate to SG and TF (32.1 g CP/kg; 410 g IVTDMD/kg; 5,160 kg DM/ha). Leaf sub‐samples of NWSG indicated greater forage nutritive value compared to whole plant samples (e.g., SG: 65 vs 27 g CP/kg respectively). This indicates that selective grazing could allow superior outcomes to those expected from whole plant NWSG nutritive values. Although consistently nutritionally inferior to TF, further research could reveal strategies to make stockpiled NWSG economically useful to livestock managers.

A Comparison of Native Grass and Triticale Pastures during Late Winter for Growing Cattle in Semiarid, Subtropical Regions

“…Temperatures were also slightly to well-above average for most months during the native grass growing season (about March through October at this location). Tilhou et al [6] reported that native tall prairie PWSG (e.g., Panicum virgatum, Adropogon gerardii, Sorghastrum nutans) were fully dormant in the upper humid, subtropical USA by late September. Temperatures after triticale planting each year (Table 2) were sufficiently warm to promote germination and growth of winter cereal forages [18], and irrigation was applied as needed throughout the winter cereal growing season to further promote growth [19].…”

“…Options for grazing in semiarid, subtropical environments include native grasses (predominantly actively growing or dormant perennial warm-season grasses, PWSG), winter cereals and other annual or perennial cool-or warm-season domesticated pastures, crop residues, and grain crops [1,5]. During their period of active growth from spring through summer, native PWSG can provide Agronomy 2022, 12, 545 2 of 11 adequate nutrition for growing cattle [6]. Native PWSG also are available for grazing after they become dormant in autumn; however, plant maturity and weathering reduce their nutritive value, making them nutritionally inadequate to support most classes of livestock, especially in regard to crude protein (CP) [6,7].…”

“…During their period of active growth from spring through summer, native PWSG can provide Agronomy 2022, 12, 545 2 of 11 adequate nutrition for growing cattle [6]. Native PWSG also are available for grazing after they become dormant in autumn; however, plant maturity and weathering reduce their nutritive value, making them nutritionally inadequate to support most classes of livestock, especially in regard to crude protein (CP) [6,7]. Protein supplementation is often required with dormant PWSG, but their use is considered economically viable due to their potentially high forage accumulation [6,8].…”

“…Native PWSG also are available for grazing after they become dormant in autumn; however, plant maturity and weathering reduce their nutritive value, making them nutritionally inadequate to support most classes of livestock, especially in regard to crude protein (CP) [6,7]. Protein supplementation is often required with dormant PWSG, but their use is considered economically viable due to their potentially high forage accumulation [6,8]. In the SHP, winter cereal forages are used extensively for grazing [9], especially by stocker (growing) cattle from November into May [1,4].…”

Editorial: Grass and Forage Science – 75 years of impact and service to the science of grasslands

“…The journal has seen a marked increase in the number of submissions of papers describing the science of warm-season grass systems, both in traditional tropical environments and in more temperate environments. These papers have encompassed the continuum of native and naturalized pastures (Tilhou et al, 2019), breeding and selection (de Fig ueiredo et al, 2019), agronomy (Boschma et al, 2019;Ruolo et al, 2019;Silva et al, 2019) and beef (Euclides et al, 2019) and dairy (Lima et al, 2019) production systems. This trend is likely to continue as we explore the complementarity of temperate and warm-season forages under changing climatic conditions.…”