Why make stink silage?

On many farms the familiar smell of silage is the sickly cloying smell of butyric acid.

This smell gets you ordered to take a shower when you come in for breakfast after feeding out. It’s the smell that makes most townies hold their noses. 

Many farmers naturally associate this smell with silage. It is prevalent on most farms when silage is being fed. Yet good silage shouldn’t smell at all. The smell signals secondary fermentation is causing butyric acid to form within the silage, and it means the silage has lost some of its nutritional value. 

Good quality fermentation should be purely based on lactic acid – which has very little smell.

What’s going on in the silage?

As mentioned, butyric acid forms during secondary fermentation produced by aerobic clostridial bacteria. This fermentation is indicative of decomposition of the naturally formed (anaerobic) lactic acid.

Aerobic fermentation degrades much of the original protein in the grass. Some farmers are naturally confused because butyric acid fermented silage is so common here in New Zealand they inherently associate the butyric acid smell with silage.

Added to this dilemma, butyric acid fermented silage, while still being nutritionally degraded, can be very stable. Its high acidity levels can make it largely immune to moulds and further degradation.

But at this point the cost has already been paid: this butyric acid fermented silage has lost much of its protein -- used up during fermentation.

Good silage making is a fine art.

Achieving good silage depends on many factors, most notably good timing and good technique. The other factor at play is technology. This one can sometimes turn a sub-standard crop, or one harvested in less-than-perfect weather conditions, into silage that retains good feed quality. 

Provided the silage making technique is robust, a combination of high technology harvesting machinery and the use of a quality inoculant can make the difference between good quality silage, ordinary silage or at worst a real disaster. 

Of course, when everything comes together perfectly, using good technology in the form of a silage inoculant will insure an even better quality end product. New Zealand farmers have the ability to make silage that is as good as anything made on European farms, despite many European farmers treating silage making as a true art form.

In a perfect world, silage would be made when a crop was harvested at its nutritional peak, the grass would be dried down to the perfect drymatter level, it would then be harvested with the best technology equipment available and then compressed into a concrete pit designed to exclude all air with an airtight cover seal.

But challenges happen.

New Zealand weather conditions make it particularly hard during the harvesting season. Add to this problem the fact that grass grows very fast here and at that time of the year there is often a shortage of available harvesting capacity. The result can be silage that is harvested at a less-than-optimal time. Weather conditions dictate this and the drymatter level of the ensiled grass may not always be adequate due to crops having to be harvested within very tight weather windows.

This is where a high technology inoculant can make all the difference.

Bonsilage is a silage inoculant due for launch in New Zealand this year. Developed and made in Germany by Provita GmbH, it has been successfully used in Europe since 2000. Bonsilage uses specifically selected living bacteria strains formulated to produce superior forage quality under varying conditions.

• Chris Balemi is managing director of Agvance Nutrition.