Submitted to: Forage Focus
Publication Type: Popular Publication
Publication Acceptance Date: 2/25/2021
Publication Date: 3/12/2021
Citation: Bleier, J.S., Coblentz, W.K. 2021. Evaluation of warm-season annuals for grazing in Wisconsin. Forage Focus. p. 8-9, 11. March 2021.
Technical Abstract: Grazing-based dairy operations require productive, high-quality forages that can support the nutritional needs of mid-lactation dairy cows. In this study, six summer-annual cultivars were compared for growth characteristics, yield, and in-situ fiber digestibility across three harvest cycles at both Prairie du Sac and Marshfield, WI. Two cultivars each of sudangrass, sorghum-sudangrass, and pearl millet were planted in early June at both locations. Within each forage type, one cultivar exhibited a distinctly shorter growth habit, either possessing the brachytic dwarf trait or was described as having a leafy, compact structure, while the other entry exhibited taller growth characteristics. Within forage type, taller-growing cultivars frequently exhibited yield advantages over dwarf or shorter-growing cultivars, but the shorter-growing cultivars generally had greater percentages of leaf tissue, which is an especially relevant characteristic within a grazing context. Although assessed before physiological maturity, dry matter (DM) yield was positively related to canopy height, and increased linearly at a rate of 1062 lbs DM/acre/week across the three harvest cycles. Forage type and cultivar had relatively minor effects on concentrations of fiber (NDF), but these concentrations were 8.2 percentage units less in leaf compared to stem tissue. Finally, NDF digestibility was greater for shorter-growing cultivars by an average of 2.5 percentage units of NDF when considered across all locations, cultivars, and harvest weeks. Generally, the dwarf or shorter-growing cultivars, as well as PM cultivars, that were evaluated under the conditions of this trial displayed characteristics more suitable for a grazing application, but selection on that basis would require a compromise with yield.