Digestible Dry Matter, Crude Protein, and Dry Matter Yields of Grazing‐Type Sorghum Cultivars as Affected by Harvest Frequency1

Abstract

Abstract‘Piper’ sudangrass, a sudangrass hybrid ‘Trudan II,’ and six sorghum ✕ sudangrass hybrids were variously managed in 1965 and 1966 to provide yield and compositional data. At heights of 46 cm (management A), five harvests resulted; at 92 cm (B), three harvests; at 137 cm (C), two harvests; and hard dough (D), one harvest. Percentages of crude protein and in vitro digestible dry matter (IVDDM) were highest for frequently harvested forage. Yields of dry matter, crude protein, and IVDDM were 27, 10, and 22% greater, respectively, for A (5 harvests) over B (3 harvests). Comparing B to C (3 to 2 harvests) total crude protein yields decreased 4% but dry matter and IVDDM yields increased 23 and 18%, respectively. From C to B (2 to 1 harvest) yields of dry matter, crude protein, and IVDDM were 86% more, 17% less, and 52% more, respectively. Piper was generally inferior to either Trudan II or one or more of the sorghum ✕ sudangrass hybrids. Trudan II was significantly higher yielding in dry matter, crude protein, and IVDDM over all managements as compared to Piper.Over all managements, Trudan II was significantly higher in crude protein yield than the mean of six sorghum ✕ sudangrass hybrids whereas differences in yields of dry matter and IVDDM were not significant. Sorghum ✕ sudangrass hybrids were definitely superior under D (1 harvest) management. While the sorghum ✕ sudangrass hybrids and Trudan II were both superior to Piper under multiple harvest (A,B,C managements), the sudangrass hybrid (Trudan II) should be given strong consideration because of its known advantage in lower prussic acid potential.