22 November 1996


How do forage additive approval schemes compare across Europe?

Robert Davies reports

BY LAW all silage additives sold in France, including products made elsewhere, have to obtain provisional authorisation for sale (PAS).

This is awarded if the composition of the product "suggests, or indicates, that its application may improve the efficiency of silage fermentation". Companies applying for PAS on a product must submit a dossier providing the additives commercial name, and details of its composition and the purity of its components.

Active ingredients must be listed, accompanied by information on the manufacturing process and quality control procedures. Proof that the product will not adversely affect human or animal health, or the environment must be supplied, with comprehensive safety procedures for people handling it.

For biological additives clones of the bacteria used in the inoculum must be deposited in an official bank. The number and vitality of the micro-organisms declared by the manufacturer must be assessed and verified by two authorised French laboratories.

PAS is awarded for four years, during which time the efficacy of the product has to be tested and demonstrated. If approved the additive is granted full registration. The scheme has been operating for 10 years and 27 products are fully registered.

Experimentation required to obtain full approval is carried out by the feed evaluation unit of the National Institute for Agricultural Research (INRA). Silages made using the product are submitted for approval, together with a negative control sample made without additive, and a positive control made using formic acid at approved rate for the type of herbage involved.

Additives are approved only if application produces results that are at least similar, or close to, those obtained with the positive control. Trials on new additives are carried out on three different forages. Chemical products are assessed on one ryegrass, one cocksfoot and one lucerne variety. Biologicals are tested on three ryegrasses, but approval is only given for application on forages that are sufficiently high in water soluble carbohydrates, such as ryegrass, brome, and immature whole-crop cereals.

With biologicals only the quality of conservation is taken into consideration. During testing of chemical additives sheep are used to ensure that neither digestibility nor intake of the silage is depressed by using the product. Assessments of the effect of feeding silage made with the product to growing animals or dairy cows are not required for full approval, but manufacturers can attempt to boost sales by publishing independently verified results of such investigations.

There are 10 fully approved chemical additives on sale in France. Most are based on formic acid, and may be used on all types of silage. A total of 14 biological additives have been either fully approved for use in forages rich in sugars only, or for application to other forages if combined with molasses to achieve at least 12% water-soluble carbohydrates in the dry matter.

Another three products are approved for increasing the aerobic stability of maize silage when silos are opened. Supporters of the approval scheme admit that the tough procedures have limited the number of products on the market, but claim that silage additive quality has improved.

Efforts to get a European silage additive approval scheme underway unfortunately have a low political priority.


&#8226 All products require PAS status.

&#8226 Product efficacy monitored.

&#8226 Twenty-seven products fully registered.

&#8226 Approval trials by INRA.