Evaluation of five C4 forage grasses in the tall Fescue Belt.

Across much of the eastern United States, tall fescue [TF; Schedonorus arundinaceus (Schreb.) Dumort.], a cool‐season (i.e., C3) perennial grass, is the primary forage for pasture systems, thereby leaving producers vulnerable to reduced summer forage production and drought. Warm‐season (i.e., C4) forages can complement existing production systems by supplementing summer forage production and drought resiliency. Therefore, our objective was to compare five, C4 forage options in a grazing trial: switchgrass (SW; Panicum virgatum L.), eastern gamagrass (EG; Tripsacum dactyloides L.), a big bluestem (Andropogon gerardii Vitman) and indiangrass (Sorghastrum nutans L. Nash) blend (BBI), bermudagrass (BG; Cynodon dactylon L. Pers), and crabgrass (CG; Digitaria sanguinalis L. Scop.). Research was conducted 2014–2016 at two locations in Tennessee. Weaned beef heifers (237–242 kg initial weight) grazed 1.2‐ha pastures with three replications per species and location. Average daily gains (kg d−1) (0.62 [BBI], 0.41 [BG], 0.44 [CG], 0.42 [EG], 0.51 [SW]), grazing days (d ha−1) (412 [BBI], 459 [BG], 455 [CG], 664 [EG], 617 [SW]), and total gain (kg ha−1) (259 [BBI], 186 [BG], 200 [CG], 276 [EG], 315 [SW]) all varied among forages (P <.001). Similarly, forage nutritive values differed (P <.001) among forages: season‐long crude protein ranged from 94 (BG) to 115 (CG and EG) g kg−1, neutral detergent fiber (NDF), 601 (CG)–680 (SW) g kg−1, and acid detergent fiber (ADF) 379 (BG)–417 (EG) g kg−1. These forage options should be evaluated in the context of TF pastures to establish a broader understanding of their contribution within an overall forage system. Core Ideas: The C4 grasses provide a beneficial complement to C3‐dominated pasture systems.Native grasses tended to have greater rates of gain and grazing days than bermudagrass or crabgrass.Overall, rates of gain for the forages in this study were lower than in comparable studies.Native grasses had greater total gain per hectare than bermudagrass or crabgrass.Bermudagrass and crabgrass provided more grazing days during late summer than native grasses. [ABSTRACT FROM AUTHOR]