Intake, digestibility, and nitrogen balance by sheep offered ensiled tall fescue, meadow fescue or orchardgrass that was fertilized with dairy slurry or urea

Authors: DIAZ, JOSE - University Of Arkansas; COFFEY, KENNETH - University Of Arkansas; Coblentz, Wayne; PHILIPP, DIRK - University Of Arkansas; NIYIGENA, VALENS - University Of Arkansas

Submitted to: Animal Feed Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2022
Publication Date: 9/17/2022
Citation: Diaz, J.M., Coffey, K.P., Coblentz, W.K., Philipp, D., Niyigena, V. 2022. Intake, digestibility, and nitrogen balance by sheep offered ensiled tall fescue, meadow fescue or orchardgrass that was fertilized with dairy slurry or urea. Animal Feed Science and Technology. 292(2022):115447. https://doi.org/10.1016/j.anifeedsci.2022.115447.
DOI: https://doi.org/10.1016/j.anifeedsci.2022.115447

Interpretive Summary: Silage intake and utilization by ruminants can be affected by several factors including fertilization and forage type. The objective of this study was to evaluate intake, digestion, and N balance by sheep offered three different grasses fertilized with either urea or dairy slurry. Plots (0.23 ha) of meadow fescue, tall fescue, or orchardgrass were fertilized with urea (52 kg N/ha) or dairy slurry (71,150 L/ha; 48 kg N/ha) on 2 July 2018 following an initial harvest on 29 June 2018. A second harvest was subsequently baled 6 August at approximately 57% moisture and wrapped in 7 layers of plastic film. In this study, applications of dairy slurry tended to yield greater concentrations of butyric acid in resultant silages, but overall had inconsistent effects on silage fermentation that were not clearly associated with subsequent intake or digestibility by sheep. Consistent with other reports, meadow fescue exhibited generally better characteristics of dry matter, organic matter, and fiber digestibility than the other perennial grasses. Meadow fescue appears to be a viable cool-season forage option as an alternative to the more prevalent tall fescue and orchardgrass forages based on chemical composition, along with greater intakes and digestibility. However, based on previous reports, producers should exercise greater management to enhance its persistence and be willing to accept lower yields compared with other, more prevalent cool-season forages.

Technical Abstract: Silage intake and utilization by ruminants can be affected by several factors including fertilization and forage type. The objective of this study was to evaluate intake, digestion, and N balance by sheep offered three different grasses fertilized with either urea (C) or dairy slurry (S). Plots of meadow fescue (MF), tall fescue (TF) or orchardgrass (OG) were fertilized with urea (52 kg N/ha; MFC, TFC and OGC) or slurry (71,150 L/ha; MFS, TFS, and OGS) on 2 July 2018 following an initial harvest on 29 June 2018. A second harvest was baled 6 August at approximately 57% moisture and wrapped in plastic. Eighteen lambs (59 ± 1.5 kg) were allocated randomly to one of the 6 treatment combinations to provide 3 lambs per treatment within each of 3 periods consisting of a 10-d adaptation and 7-d total fecal and urine collection. Data were analyzed as a 2 × 3 factorial arrangement using PROC MIXED of SAS. Crude protein (CP) concentrations were greatest from MFS and lowest with OGS (P < 0.05) and aNDF, ADF and lignin were greater (P < 0.05) from OG vs TF and MF. Lactic acid concentrations (g/kg DM) in baled silages were greatest from TFC and lowest from MFC and OGC (P < 0.05). Dry matter (DM) and organic matter (OM) intakes (g/kg BW), digestibility and digestible DM and OM intakes (g/kg BW) were greater (P < 0.05) from MF than from TF and OG and digestible OM intake was greater (P < 0.05) from C vs. S. Digestibility of NDF (g/kg NDF) was greater (P < 0.05) from MF and OG vs. TF. Nitrogen retention (g/kg N intake) tended (P = 0.08) to be greater from MF vs. OG and urine N (g/kg N intake and g/kg N excreted) was greater from TF and OG compared with MF. Therefore, meadow fescue has the potential to provide a higher-quality forage that will increase intake and digestibility over more conventional orchardgrass and tall fescue. Fertilization with dairy slurry affected certain forage chemical components but did not impact forage intake or digestibility when applied 35 d prior to a subsequent harvest.