20 November 1998

Right product? List holds the answer

IN recent years, a number of surveys of silage analyses from commercial farms have shown the benefits of promoting better silage fermentation through the use of effective silage additives.

Other additive types have proved their potential for restricting or delaying aerobic deterioration during the feedout phase and for reducing effluent outflow.

The Forage Additive Approval Scheme (FAAS), now in its sixth year, has brought independent unbiased assessment of product efficacy and this, together with the monitoring of product quality and content, means that todays farmer has more reliable information on additives than ever before.

Despite this, the large number of products in the scheme – 92 this year – means that choosing the right additive for your own situation remains difficult. The first stage in narrowing choice is to select the right product type. Here, consider why you are using an additive and what you expect of it. In most cases you will be looking either to influence fermentation, enhance aerobic stability or reduce effluent.

Traditionally, many viewed additives as an insurance against a poor fermentation. This was especially true for difficult ensiling conditions – grass low in dry matter and/or sugar, often with bad weather thrown in.

Twenty-five years ago the answer was an acid additive, with or without formalin. Nowadays formic acid additives are still at the forefront for effectiveness in these conditions, directly acidifying the crop to bring down the pH to about 4. But acids are not user-friendly and must be handled carefully.

Where conditions are less demanding, an effective inoculant may bring even greater benefit in increasing speed of fermentation and enhancing animal performance. Inoculants contain bacteria primarily selected for their ability to convert sugar to acid, mainly lactic acid, thus maximising use of the grass sugar to bring pH down. Many also contain enzymes, designed to increase the sugar substrate for the bacteria.

A glance at the list of acid or inoculant products – and molasses – shows that nearly all have proven efficacy in fermentation benefit. The next stage is to look at the products in which fermentation enhances animal performance, those with approvals in Categories A1 (Liveweight gain) and A2 (Milk Production).

Consider too, C4, the category indicating approval for reducing ensiling losses. While good pit management is the key to maintaining losses at an acceptable level, any assistance the additive can provide is most welcome.

A number of additives have been developed to help control aerobic spoilage. Some of the inoculants have added bacterial species which produce propionic or acetic acid while other products are based on various acid salts. Aerobic stability problems are greatest with high dry matter grass silage and with maize silage.

One other special category is that of effluent reduction. While some inoculants have demonstrated benefits in this, a sugar beet pulp-type product is more likely to be effective over a wider range of dry matters.

There is no single additive which is best in every situation.

Last, but certainly not least, should you always use an additive? Of course not – simple economics tell you that the return has to exceed the cost. Unfortunately, it is not easy to guess the outcome of not using an additive. &#42