|Sauer, Thomas - Tom|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2005
Publication Date: 1/3/2006
Citation: Scarbrough, D.A., Coblentz, W.K., Ogden, R.K., Turner, J.E., Humphry, J.B., Coffey, K.P., Daniel, T.C., Sauer, T.J., Jennings, J.A., Kellogg, D.W. 2006. Nitrogen partitioning and estimates of degradable intake protein in wilting orchardgrass and bermudagrass hays damaged by simulated rainfall. Agronomy Journal. 98:85-93. Interpretive Summary: In much of the Southeastern U.S., harvesting hay is complicated by weather conditions as high humidity and frequent rains occur during times when hay crops mature. Thus, producers often face a choice between baling hay before it has dried to the optimum moisture content, delaying harvest until suitable weather occurs, or subjecting their hay crop to rain damage. Baling hay that is too wet, waiting too long to harvest, and letting rain fall on mown grass all decrease the quality of the hay as animal feed. The purpose of this study was to measure the changes in protein content of orchardgrass and bermudagrass hay that was subjected to simulated rainfall at varying moisture contents. It was found that protein content of the forages changed more when the grass was dry before being rained upon and that the protein content of orchardgrass changed more than bermudagrass. These results are important to producers trying to optimize the digestive quality of forage by achieving timely harvest without rain damage.
Technical Abstract: This study investigated the effects of simulated rainfall on nitrogen (N) partitioning and concentrations of degradable (DIP) or undegradable (UIP) intake protein for wilting orchardgrass (Dactylis glomerata L.) and bermudagrass [Cynodon dactylon (L.) Pers.] hays. Orchardgrass forage was wilted to 674, 153, or 41 g kg-1 of moisture (WET-O, IDEAL-O, and DRY-O, respectively) in the field prior to applying the simulated rainfall (0, 12, 25, 38, 51, 64, or 76 mm). For WET-O, DIP (g kg-1 CP) increased cubically (P = 0.020) with simulated rainfall, but the overall range of response was small (653 to 673 g kg-1 CP). Estimates of DIP (g kg-1 CP) for both IDEAL-O and DRY-O decreased by 46 and 25 g kg-1 CP, respectively, between the 0 and 76-mm rainfall increments; for IDEAL-O, these decreases occurred in a linear (P < 0.0001) pattern, while quadratic (P = 0.009) and linear (P = 0.029) effects were observed for DRY-O. Bermudagrass forage was field wilted to 761, 400, or 130 g kg-1 of moisture (WEB-B, MID-B, and IDEAL-B, respectively) and evaluated similarly. For WET-B and MID-B, DIP (g kg-1 CP) was not affected (P > 0.05) by simulated rainfall. In contrast, quartic (P = 0.019) and linear (P = 0.002) increases were observed for IDEAL-B, but these responses were confined primarily to changes between the undamaged (0-mm) control and the initial 12-mm rainfall increment. Generally, N and/or protein fractions were more susceptible to change for dry compared to wet forages, and for orchardgrass compared to bermudagrass.