Retention of H<sub>3</sub>PO<sub>4</sub> and NH<sub>4</sub>OH by the fibrous components of oat (<i>Avena sativa L.</i>) forage.

Because of its importance as fodder, the treatment of oat straw with phosphoric acid (H3PO4) and ammonium hydroxide (NH4OH) was studied. Five hundred g of oat straw were sprayed separately with 1 molar aqueous solutions of these chemical compounds and after 0, 8, 16, 24, 24, 32, 40 and 48 hours, without washing, samples were taken for analysis. The response variables determined were neutral detergent fiber (NDF), acid detergent fiber (ADF), cellulose, lignin (LDA), silica and hemicellulose. The effects of chemical compounds (analysis of variance, p<0.05) and time (Tukey, p<0.05) were evaluated. Using all data, Hem was higher with H3PO4, while FDA, ADL, cellulose and silica were higher with NH4OH. Overall, most response variables with H3PO4 and only NDF, FDA and cellulose with NH4OH were greater (retention effect) at 8 hours than at 0 hours of treatment. From 16 to 48 hours with H3PO4, FDN, FDA and cellulose decreased (hydrolytic effect) and no variable did so with NH4OH. During 8 hours of treatment, FDN, FDA, LDA, cellulose and silica retained 9.98, 8.84, 1.87, 7.65 and 2.00% of H3PO4, respectively, while FDN, FDA and cellulose retained 4.01, 4.84 and 4.11% of NH4OH, respectively. Additionally, at 48 hours of treatment, a hydrolytic effect was observed with H3PO4. In conclusion, NDF retained more H3PO4 than NH4OH and in turn was more hydrolyzed by the former than by the latter.