Evaluation Of Eastern Gamagrass And A Sorghum X Sudangrass For Summer Pasture

Improved summer forage production is important in forage systems dominated by cool-season perennial grasses. Improved forage may be especially important for heifer [Bos taurus (L)] development. Therefore, we compared two summer forage options, a perennial, eastern gamagrass [Tripsacum dactyloides (L.) L.], and a widely used summer annual, sorghum [Sorghum bicolor (L.) Moench] x sudangrass [Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud.) de Wet & Harlan] hybrid, as options for providing summer pasture for bred heifers (418 +/- 31 kg initial body mass). We used put-and-take grazing (i.e., routine adjustment of stocking to maintain target canopy conditions) to evaluate pasture characteristics, animal performance, and pasture productivity, 2013-2015. Crude protein of eastern gamagrass (EG) exceeded (P = 0.01) that of the sorghum x sudangrass hybrid (SXS), but FM, ADF, and NDF were all similar between the two forage types. Although SXS provided greater ADG (P = 0.03) in two of three years, EG provided twice as many AD ha(-1) (P = 0.03) and consequently, greater (P < .001) GAIN in two of three years. Calving rates (89%) did not differ between the two forages. Increased N rates (67 vs.137 kg ha(-1) N) did not alter EG pasture characteristics but appeared to improve GAIN (279 and 355 kg ha(-1), respectively). Cost of gain was greater for SXS in 2014 and 2015 ($1.71 and $1.64 kg(-1)) than for EG ($0.62 and $0.62 kg(-1)). Both EG and SXS could be useful for providing summer forage for bred heifers.