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

Silage intake and utilization by ruminants can be affected by several factors including forage type and fertilization. The objective of this study was to evaluate intake, digestion, and N balance by sheep offered three different ensiled grasses following fertilization 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 allo-cated randomly to one of the 6 treatment combinations to provide 3 lambs per treatment within each of 3 periods for a total of 9 replications per treatment. Each period consisted of a 10-d adap-tation and 7-d total fecal and urine collection. Data were analyzed as a 2 x 3 factorial arrange-ment using PROC MIXED of SAS. Post-ensiled crude protein (CP) concentrations were greatest from MFS and lowest from OGS (P < 0.05), and aNDF, ADF and lignin were greater (P < 0.05) from OG vs TF and MF, regardless of fertilization. Lactic acid concentrations (g/kg DM) in baled silages were greatest from TFC and lowest from MFC and OGS (P < 0.05). Dry matter (DM) and organic matter (OM) intakes (g/kg BW and BW0.75), digestibility and digestible DM and OM in-takes (g/kg BW and BW0.75) were greater (P < 0.05) from MF than from TF and OG across fertilization type and digestible OM intake was greater (P < 0.05) from C vs. S across forages. Digestibility of NDF (g/kg NDF) was greater (P < 0.05) from MF and OG vs. TF across fertilization treatments. 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 across fertilization treatments. 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 and reduced organic matter intake but did not impact digestibility when applied 35 d prior to a subsequent harvest.

Automated summary

This study evaluated the intake, digestion, and nitrogen balance of sheep offered different ensiled grasses following fertilization with either urea or dairy slurry. Meadow fescue was found to have higher-quality forage that increased intake and digestibility compared to orchardgrass and tall fescue. Fertilization with dairy slurry affected certain forage chemical components but did not impact digestibility when applied 35 days prior to a subsequent harvest.