Sodium nitrite-based additives improve the conservation and the nutritive value of guinea grass silage

Abstract

As producing tropical grass silage with high feeding value is still a challenge, we examined the effectiveness of sodium nitrite-based additives on guinea grass (Megathyrsus maximum cv. Mombaça) silage quality. The forage was mechanically harvested from four 3-ha fields and divided into 5 piles per field to receive one of the following treatments (fresh matter basis): no additive (control), soybean hulls (100 g/kg; SH), sodium nitrite (1 g/kg; NIT), sodium nitrite (1 g/kg) + hexamine (0.65 g/kg; NIT+HEX), and formic acid (85%) (4 mL/kg; FA). Sodium nitrite-based additives (sodium nitrite applied alone or in combination with hexamine) and FA were capable of curtailing clostridial development, resulting in lower concentrations of NH3-N and n-butyric acid and reduced dry matter (DM) loss during fermentation, whereas protein quality and hygienic quality (reflected by lower Clostridium counts) were improved. A strong linear relationship was detected between the concentrations of butyric and valeric acids and DM losses during fermentation (R2 = 0.87, P < 0.01). Addition of SH improved DM degradability and slightly decreased fermentation losses, but it did not lead to butyric acid-free silages. The use of FA and sodium nitrite-based additives was effective in improving the fermentation quality of tropical grass silage, and the combination with hexamine was superior to the sole use of sodium nitrite. All treatments improved in vitro DM degradability over untreated silage. Only NIT, NIT+HEX and FA increased the concentration of rumen-undegradable protein, with NIT+HEX and FA outperforming NIT. Sodium nitrite-based additives have the potential to improve the fermentation and the nutritive value of guinea grass silage.