Effects of urea addition on the fermentation of sorghum (Sorghum bicolor) silage

Abstract

This study was conducted to evaluate the effects of urea addition on fermentation characteristics, losses and chemical composition of silage of sorghum (Sorghum bicolor) ‘BRS Ponta Negra’. The sorghum plant was chopped and treated with different levels of urea (0.1756, 0.3512, 0.7024 and 1.4048 g per 10 kg fresh forage for the respective proportions of 0.5%, 1.0%, 2.0% and 4.0% of forage (dry matter [DM] basis), and packed into quintuplicate experimental silos to determine its effects on fermentation, losses and chemical composition of sorghum silages. Addition of urea increased lactic acid bacteria up to the level of 60 g kg⁻¹ (DM basis). Compared with control silage, the addition of urea (p < 0.05) reduced DM losses. Urea-treated silages linearly increased (p < 0.05) the ammoniacal nitrogen and crude protein contents, and linearly reduced (p < 0.05) the ethanol content. The pH in urea-treated silages indicated better preservation of substrates obtained from fermentation. The intermediate level of 2.0% urea additive can be used to improve fermentation, reducing losses in sorghum silage without compromising lactic acid production. However, the addition of 0.5% and 1.0% urea to sorghum silage is sufficient to improve aerobic stability.

Keywords: chemical additive, fermentation profile, forage preservation