Chemical fractionation of carbohydrate and protein composition of corn silages fertilized with increasing doses of nitrogen

Composição química fracional de carboidratos e de proteínas de silagens de milho fertilizadas com doses crescentes de nitrogênio

ABSTRACT:

The use of nitrogen fertilizers in corn crops for silage can improve both production and, theoretically, nutritional quality, especially carbohydrate and protein fractions, thereby optimizing animal production. Thus, the aim of this study was to evaluate the effect of increasing levels of nitrogen fertilization in carbohydrate and protein fractionation on the resulting corn silage (Zea mays L.). Nitrogen fertilization was carried out in the urea form (45-00-00) in V5 stage, at the following doses: T₁: 0kg N ha^-1; T₂: 45kg N ha^-1; T₃: 90kg N ha^-1; and T₄: 135kg N ha^-1. Crops were harvested at R4 stage and submitted to ensiling in experimental PVC silos. The chemical composition of the resulting silage was evaluated after silo opening. There was no statistical difference (P<0.05) in the average contents of gross protein (GP), as well as its C fraction, showing that increasing nitrogen doses in coverage linearly increased GP and linearly decreased its C fraction. For total carbohydrates, there was a linear decreasing behavior due to such consumption with the highest levels of nitrogen applied. Increased nitrogen fertilization dose in corn also linearly enhanced pH in the resulting silage. Therefore, nitrogen increases in coverage can alter carbohydrates and GP fractionation of corn silage, with increases in soluble fiber, GP, and pH, and reduction in the protein indigestible fraction.

Key words: starch; organic acids; C fraction; pH; solubility