Evaluation of eastern gamagrass and a sorghum × sudangrass for summer pasture
2020
Keyser, Patrick D. (Patrick David) | Lituma, Christopher Manuel | Bates, Gary E. | Holcomb, Elizabeth D. | Waller, John C. | Griffith, Andrew P.
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] × 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 × 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.
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