|Remick, Elizabeth - University Of Wisconsin|
|Akins, Matthew - University Of Wisconsin|
|Su, Huawei - University Of Wisconsin|
Submitted to: Popular Publication
Publication Type: Popular Publication
Publication Acceptance Date: 6/1/2016
Publication Date: 6/6/2016
Citation: Remick, E., Akins, M., Su, H., Coblentz, W.K. 2016. Evaluation of yield and nutritive value of photoperiod-sensitive sorghum and sorghum-sudangrass. Popular Publication. Midwest Forage Assn. Project Reports 2015.
Technical Abstract: Moderate quality forages that meet the nutrient requirements of dairy heifers are not grown commonly; however, this forage management option could have a positive impact on the dairy industry. Heifers gain excessive bodyweight when they consume diets high in energy; this is especially true post-puberty, and may negatively impact first lactation production. Replacement dairy heifers are typically offered forage-based diets comprised of corn, alfalfa, or grass silages. Corn silage is energy dense (70-75% TDN, DM basis) and exceeds the requirements for 900-1200 lb heifers (62% TDN). Sorghum and sorghum-sudangrass have moderate nutritive quality (higher fiber, lower starch), and could be a forage alternative with potential to limit weight gains to acceptable targets (1.8 to 1.9 lbs/day). New types of sorghum (photoperiod sensitive; PS) are marketed currently as forage or biofuel crops. Some PS varieties stay vegetative until total daylight reaches 12 hours and 20 minutes (mid-September), thereby allowing the plant to accumulate greater forage mass. The objective of this study was to evaluate the yield and nutritive value of PS forage sorghum and sorghum-sudangrass compared to non-PS sorghum, non-PS sorghum-sudangrass, or corn silage following establishment on 2 dates with single or multi-cut harvest strategies. Results of this trial suggest that some sorghum varieties are able to produce similar forage yields to corn throughout central Wisconsin. These varieties may provide a significant yield of moderate quality forage for heifers or other livestock with moderate nutritive needs. For high tonnage, our results clearly indicate that a single-cut system is preferred over a multi-cut strategy. The alternative forages evaluated in this experiment can be useful in synchronizing the energy needs of pregnant dairy heifers (58-62% TDN) with the energy density of blended forage-based diets. In many cases, TDN concentrations were similar to those required by pregnant dairy heifers, and in some cases, could dilute the excess energy of corn silage that many producers desire to use. In all cases, forage sorghums, sorghum-sudangrasses, or corn silages had insufficient protein to meet the requirements of dairy heifers, and would require supplementation, or blending with other high-protein forages.