22 November 1996


Farmers are beginning to make a better use of the UKASTA Forage Additives Approval Scheme. Stuart Jones, a midlands-based independent nutrition consultant, reports

AFTER initial concern about the way some consultants and salesmen were misrepresenting the objectives and findings of the scheme to farmers, there now seems to be a better understanding that no additive is ideal for all situations.

In recognition of this, the approval is split into nine separate categories (see table opposite), so farmers must select with care.

When selecting an additive, first answer the question: "In preserving this crop as silage what are my most important objectives?"

In almost all circumstances it will be important to cut losses by achieving good control of fermentation, so the additive of choice should certainly have category C1 approval. Again, most farmers will be concerned to reduce the risk of losses associated with either effluent during storage and/or rapid aerobic spoilage after the clamp has been opened. Additives with category C3 and C2 approvals, respectively, should help achieve that.

Other factors such as improving animal performance (category A) may be of less practical use because many farmers will not have enough extra silage to let their livestock achieve more production from forage. Since grass silage is not necessarily the cheapest option, and since cows eat more dry matter when the diet contains a mixture of forages, Mr Jones suggests that alternatives such as forage maize and whole- crop wheat should also be considered.

Having decided which factors are most important – and hence which category approvals are most relevant – producers will still need to choose from a list of additives. Understandably, there is a tendency to be conservative and choose one that is well known and which may have been used before. There is nothing wrong with that, assuming it was successful, but a more recently introduced additive may be even better.

It makes sense to check the full list when it is published, taking particular note of any new products and the approvals they have received.

The discussion regarding the comparative merits of acids and inoculants continues. Strong acids are dangerous. They should be handled only by experienced workers. Their main disadvantage is that they can increase effluent. But formic and sulphuric acids, in particular, have a proven track record of improving control of fermentation, especially when conditions are poor. At least one manufacturer has developed an improved system for handling acid additives.

Modern effective inoculant additives have been shown to enhance fermentation and animal performance, especially in crops of moderate dry matter content (22-24%). Some have the added advantage of reducing effluent. The choice will not always be clear cut, so it could pay to take advice from an independent consultant – recognising that the decision should also take account of the crop to be ensiled, the weather and the results of any analyses of samples taken before cutting.

The FAAS is entirely voluntary, so it is possible that some companies may choose not to join. That probably means that no independent assessment of their products has been made in Britain. With so much choice available from additives on the approved register, those not included may represent less certain value for money.

That said some products will not be shown on the register published in this supplement. Although they were entered initially, the companies have not provided enough evidence for approval in even one category. It would help if this rule was modified slightly.

While the exclusion of a product makes sense if no attempt has been made to demonstrate its effectiveness, the small company working within a limited research budget deserves sympathy. It can cost over £100,000 to carry out all the studies needed at independent research institutes, considerably more than is often available especially to the smaller companies.

Where results of one or two trials have been submitted to the assessment panel and shown significant advantages over untreated crops, these products might be included on the register with a P rating (provisional) for at least another two years. That would separate them from fully approved products but at the same time reward those innovative companies which have achieved at least some independent assessment.

First aim of the FAAS, to demonstrate which factors an additive improves compared with an untreated crop under tightly controlled experimental conditions, has now been achieved for a substantial number of products. The next stage, that of monitoring the products being sold on to farms, is also in place.

Each manufacturer now has to complete a detailed questionnaire describing the active principle of the product, the quality control procedures in place during manufacture, storage and distribution and any safety aspects that may be necessary.

UKASTA has arranged for independent scientists from the official advisory services to make spot checks of storage conditions and to analyse representative samples of the commercially available additive so as to ensure the product reaching the farmer is at least as effective as the additive used in the trials.

So used correctly and as part of the overall planning of a forage conservation programme the FAAS makes a valuable contribution to improving the efficiency of livestock farms in Britain. But it is vital to use it properly to justify the substantial investment.n

Modern effective inoculants have been shown to improve silage fermentation and animal milk production performance.

Feed consultant Stuart Jones: "In preparing this crop of silage what are my most important objectives?"

Feed consultant Stuart Jones: "In preparing this crop of silage what are my most important objectives?"

Categories of the Forage Additive Approval Scheme

CategoryEffective in

Category A

A1Improving animal gains

A2Improving milkproduction

Category B

B1Improving voluntary


B2Improving digestibility

in vivo

B3Improving the efficiency

in energy utilisation

Category C

C1Improving fermentation

C2Improving aerobicstability

C3Reducing effluent

C4Reducing ensilinglosses