16 January 1998

Some silage bugs dont meet claims

INOCULANT silage additives sourced at retail outlets in September did not all deliver the live bacteria numbers claimed by manufacturers, according to a new trial. But ADAS casts doubts on the testing methods used.

Researchers Gerry Lane and Stephen Harrison, who completed the study at the Royal Agricult-ural College, Cirencester, said that of the 15 products that were tested, six failed to deliver the bacteria declared. All but two of the products tested were approved under the Forage Additive Approval Scheme (FAAS).

When products were tested for bacteria number after mixing with water in an applicator barrel, five of seven liquid-applied products failed to maintain bacteria number for the declared length of time. One was below specification six hours after dilution, despite claiming a two-day tank life.

Dry-applied products also supplied a very low number of bacteria in three of the eight samples tested.

From local suppliers

All products were bought as farmers would from local suppliers and were used and tested within two weeks, says Mr Lane. "Where storage was needed, this was according to the manufacturers recommendations, and products were mixed exactly according to their instructions supplied."

The only difference between the RAC test and FAAS assessments is that products were bought as farmers do, rather than directly from the manufacturer, he adds.

ADAS microbiology lab manager Tony Moore told FW that he was concerned about the method of testing bacteria used by RAC.

"It has taken many years of inoculant testing by ADAS to understand the differences bet-ween products. A standard test method cannot be used for all products which have different carriers. Some products actually need the bacteria removed from the carrier before testing," he says.

Dr Moore explains that there is also a wide error factor for inoculant testing, and that products must be tested up to four times before failing.

The FAAS has improved the quality of inoculants sold, he adds. However, he acknowledges that products are not tested after mixing as the RAC has done.