Growing of moderate quality forages that meet and not exceed requirements of dairy replacement heifers is not commonly done; however, it would have a positive impact on the dairy industry. It is typical for heifers to gain excessive bodyweight, especially post-puberty which negatively impacts first lactation milk production when fed diets high in energy. Replacement dairy heifers are typically fed high forage diets with a combination of corn silage and alfalfa or grass silage. Corn silage is typically high energy (70 to 75% TDN, DM basis) and exceeds dairy heifer requirements (900 to 1200 lb heifers require 62% TDN, DM) causing excess gain and overconditioning. Use of lower quality forages would reduce heifer over-conditioning. Sorghum and sorghum-sudangrass have a lower nutritive quality (higher fiber, lower starch) than corn silage and would be an alternative to reduce excess heifer weight gains.
The objective of this study was to evaluate the yield of PS forage sorghum and sorghum-sudangrass compared to non-PS sorghum, sorghum-sudangrass and corn silage. We chose to conduct the study at the Hancock and Marshfield Agricultural Research Stations due to differences in soil characteristics (silt loam soil at Marshfield and sandy soil at Hancock).