Cinética de degradación ruminal in situ de ensilado de rastrojo de maíz (Zea mays) con niveles crecientes de urea

Abstract

The urea inclusion effect on the nutritional composition and kinetics of in situ ruminal digestion on maize stubble silage was studied. Four treatments were started by adding 0, 1, 2 and 3% urea to a mixture of maize stubble with 10% molasses. 128 microsilos (3 kg/unit and 4 repetitions per treatment) were made. Experimental silages were opened at 7, 14, 21, 28, 35, 42, 49 and 56 days. The content of dry matter (MS), organic matter (OM), crude protein (PB), FND and FAD were determined. In situ degradability was obtained by Mehrez and Orskov method and the degradability of MS and PB by residue analysis with Kjeldhal method. A general linear model was used for data manipulation, using the statistical package SAS (2004), as well as Contrast option and Solver function of Microsoft EXCEL®. 35-days conservation silage (p <0.05) was observed as best treatment. Significant differences for all the variables except OM was evidenced. Urea addition was related to increase in MS and PB and decrease in FND and FAD values (p <0.01). In situ ruminal degradability of DM increased as urea level increased, except in the case of factor c, while for PB differences between treatments were not reflected. Urea addition was related to increase in MS and PB and decrease in FND and FAD values (p <0.01). In situ ruminal degradability of DM increased as urea level increased, except in case of factor c, while differences between treatments for PB were not reflected. Effective degradability was higher in MS, and with greater variability between treatments than in PB, where a more homogeneous behavior was observed. Addition of 3% urea improves the nutritional composition and degradability of maize stubble silage with molasses, making it possible for smallhorders to have an efficient and environmentally acceptable alternative animal feed supplement with this technique.