Making the best quality silage from autumn-cut grass

Making silage from autumn-cut grass can be a challenge. But getting it right can provide a highly nutritious forage. Silage consultant, Dr Horst Auerbach, offers some tips for getting the best from the last cut of the season.

Low sugar and contamination risks

Among others, adverse wilting conditions is the most critical factor. Generally lower temperatures during day and night combined with frequent dew formation in the mornings make it very difficult to increase dry matter rapidly, or at all, without extending wilting time.

The challenging conditions for autumn-cut grass silage production leave no option but to use the strongest additives we have. In combination with an unavoidably low DM content, there is a risk of high clostridia contamination due to wet soil, which is more likely to stick to the wet forage. So, the question arises as to what type of additive should be used. Clearly, inoculants cannot be an option due to their mode of action. Lactic acid bacteria work in an indirect way by producing lactic acid from available sugars which, in turn, reduces pH, and inhibits clostridia. But what if the sugar concentration is not high enough? What if ash concentration (soil contamination!) is high, which limits the effect of lactic acid on pH so that the critical pH to inhibit clostridia will not be attained? What if clostridia numbers are high? What if all three aforementioned factors are present simultaneously?

Sodium nitrite

As we do not know any of the answers to these questions at the time of chopping/baling, we cannot but rely only on the most potent clostridial inhibitor: sodium nitrite!  The action of sodium nitrite is different from that of inoculants. It directly knocks out clostridia (and their spores), thereby saving sugars for the lactic acid bacteria on the forage to facilitate a natural lactic acid fermentation process in the clamp.

Nitrite-containing additives, including MultiMax, have been widely used for decades in many European countries when ensiling conditions are challenging, such as silage production in the autumn. They are strong, they are proven, they are safe, they are not corrosive!

The data presented in the table below highlight the effectiveness of nitrite-containing additives on the fermentation quality of low DM grasses (Trial 1 and 2), even when contaminated with soil to increase clostridia numbers (Trial 2). Sodium nitrite inhibited butyric acid-forming clostridia, stimulated lactic acid production, or prevented its degradation by clostridia, and reduced protein degradation as reflected by largely reduced ammonia-nitrogen concentrations. In turn, an efficient fermentation process with lower DM losses was ensured.