Effects of Conservation Methods and Anhydrous Ammonia or Urea Treatments on Composition and Digestion of Tall Fescue

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Abstract
Tall fescue was preserved as hay (FH), hay reconstituted and ensiled (FHR) or silage (FS) and treated with no alkali (control, C), anhydrous NH3 (AA) or urea (U) in a 3 × 3 factorial design. Concentrations of NDF and hemicelluloses were reduced (P < .001) in FHR and FS vs. FH. Among forages not treated with alkali, concentrations of p-coumaric acid (PCA), but not of ferulic acid (FA), were higher (P < .05) in FS than in FH or FHR, indicating a difference in solubilization of PCA and FA relative to NDF. Rate and extent of in situ digestion of NDF and ADF were greater (P < .05) for FHR and FS than for FH and also greater for AA and U than for C. Extent of NDF and ADF digestion and concentrations of PCA and FA were not different between FHR-U and FHR-AA, but extent of NDF and ADF digestion was greater (P < .05) and concentrations of PCA and FA lower (P < .05) for FS-AA than for FS-U. Urea was more effective in reducing phenolic concentrations and improving extent of digestion when added to FHR than FS, possibly due to lower (P < .05) organic acid concentrations in FHR. Disappearance of harvested NDF due to solubilization plus digestion was similar (P > .10) for AA vs U treatment of FHR or FS but not FH. Urea added to FH was not hydrolyzed. Correlations of rate and extent of NDF digestion with FA concentration were −.66 and −.91, respectively; correlations with PCA concentration were −.40 and −.73, respectively. Cell wall xylose:glucose and arabinose:xylose ratios were not correlated with NDF digestion. Regardless of conservation method, application of AA altered forage composition and increased NDF digestion, but efficacy of U to alter forage composition and improve digestion depended on method of forage conservation. Copyright © 1988. American Society of Animal Science . Copyright 1988 by American Society of Animal Science

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