21 November 1997



Laboratory trials several years ago triggered doubts about the viability of biological silage

additives. Manufacturers and distributors have sharpened up their act since then, but care

is still needed in buying and storing such products. Peter Grimshaw reports

BACK in the 1980s, silage experts suspected that all was not what it should be with certain biological silage additives.

This was borne out by trials four years ago at Llysfasi College, Ruthin.

ADAS started a mini-survey, taking random samples of biological additives and testing them for the number of living bacteria, and then comparing them with declared levels.

Samples were taken on farms, just at the time when they were about to be used.

"We found that a significant number of the bugs had died in an alarmingly high proportion of the additives. Some were completely dead," says Tony Moore, manager of the ADAS Microbiology Laboratory, Wolverhampton. "These products are living organisms, and they will die if they are not treated nicely."

It was obvious to ADAS that this was a concern, and probably helped to account for some of the cases where biological additives had not given the expected improvement in silage quality.

"They had started off at the manufacturers as a heaving mass of living bacteria, but by the time the farmer got round to using them, they were nothing like what they should be," says Dr Moore.

"There was no intentional wrong. It was basically a question of ignorance. People at all stages, whether distributors, salesmen, farmers, and even advisers and consultants, hadnt appreciated that these products had to be treated as living organisms and not just like ordinary chemicals."

ADAS investigated further, and found that in nearly every case where there had been obvious die-off, products had either been allowed to become too warm, or had been exposed to the atmosphere.

Storage in direct sunshine, a warm office, or transport in a hot car boot is enough to do the damage. When packaging is broken and air gets in, often many more bacteria will die.

A campaign to inform manufacturers, distributors and farmers has since resulted in far fewer cases of failure.

The basic message to manufacturers was that they needed to be very clear about how their products should be stored, with guidance on temperature wherever possible, and with a use-by date. Dr Moore believes these data should be backed by credible research. Distributors and farmers were advised to check the use-by date and read and follow the instructions for handling and storage.

More recently, monitoring by ADAS has become part of the additive monitoring scheme, FAAS, run by the merchants organisation, UKASTA, to ensure that additives match their specification (see panel).

Dr Moore stresses the importance of buying FAAS approved biological additives from a reputable source that protects its distribution chain, and to avoid buying from an unknown dealer.

All this appears to have born fruit. "The standard of FAAS approved biological additives, as used by the farmer, has increased dramatically in recent years as a result of the extra attention given to storage," says Dr Moore. "The message is getting through. Products we are now sampling are bang on."

AS a sales organisation that claims to work only for its customers, ACT was among the first to take steps to ensure the biological silage additives it supplied were fully effective when they came to be used.

The firm commissioned ADAS to carry out random checks of its additives sampled from farms.

After trials, ACT invested in new packing methods intended to protect its products from heat and air. "We wont despatch additives on a Friday, for example, because we cant be sure how carriers will keep it over the weekend," says the companys product manager, Michelle Turnbull.

ACT is also looking for products that withstand storage well, and has found that those containing a cryoprotectant maintain viability better than those that do not.

Ms Turnbull emphasises the part that farmers have to play in avoiding loss of viability. She advises that some additives should be refrigerated while waiting to be used, or even put in a freezer. "Where long-term storage is envisaged, deep freezing will ensure the product is kept in prime condition.

"Farmers must appreciate that biological additives are living organisms, similar to vaccines, and they should be treated accordingly. Keeping them in a cool, dark shed out of sunlight is the minimum requirement."

Worcester-based Microferm, was among the first to make biological additives in the UK, and its product is freeze dried to maintain the organisms viability, using a crypoprotectant. Sales director, Ian Wright, says more attention to viability would benefit everyone concerned. He expects to see the FAAS scheme extended to on-farm sampling. "Storage has been a neglected issue," he says. "These products certainly do age faster, the warmer they are kept." He condemns companies that guarantee bacterial viability, because he says it is impossible to account for storage and handling conditions after manufacture.

There is one golden rule to maintain maximum viability, he says: "The cooler it is stored, the better." Microferms general advice is to store in a cold, dry place and to refrigerate if storage is to be for extended periods, such as carrying over to the next year.

Genus Live System Inoculant was launched in 1990 as a revolutionary additive intended to get round the problem of viability at the time of use by growing the culture of Lactobacillus plantarum on the farm, just before it is required for use.

The kit includes an on-farm pH test intended to show the bacteria are alive at the time of use. Live System must still be stored with care, just like other additives.

Andy Beardsmore, managing director of Ecosyl Products, says there will always be difficulties with on-farm storage. But he reckons the onus is on the manufacturer in particular to make a product that will be able to work under farm conditions. Manufacturer and distributor have a joint responsibility, he says, to make sure the farmer looks after the product when he receives it.

Ecosyl policy is to produce and distribute in such a way as to be confident that even if a farmer stores it until the following season, it will still do a good job.

But it is preferable not to carry product over. Most manufacturers do not deliver to distributors before early spring, and farmers should ask pertinent questions about the date of manufacture when ordering, if they want to be certain that they are not getting old stock.

Some companies will take product back and "rejuvenate" it, if it has been on the farm for a long time.n

Care is needed when storing inoculants to ensure bacteria numbers are maintained from manufacture to field.

Biological additives are living organisms, similar to vaccines, and should be treated accordingly.


Active ingredient monitoring under the Forage Additives Scheme is proving successful, with only two inoculant failures late in the season this year.

So reports ADAS microbiology manager Tony Moore, who runs the monitoring scheme for UKASTA. This ensures every product on the market has been tested to guarantee consistency of products delivered to producers.

Both batches of inoculants which failed this year have been taken off the market and the reasons for failure are being addressed.

Last year, the first year of testing, five out of about 100 products technically failed. But this was due to difficulties with enzymes, which are complicated to test for, and some of the testing procedures companies were using needed to be clarified. "These issues have been resolved."

The producer should be getting what was tested to give the approval scheme rating, says Dr Moore. There are no minimum standards set but the active ingredient levels are checked against manufacturers claims for the approved products. "But this is no guarantee that the product works, just that producers are receiving the product that the company initially tested."

Samples are collected twice a year from the manufacturing site or distribution depot; the first sampling is very early in the season and the second later. Of the three samples collected one is tested. If that fails the other two are tested. "Then if all three packs fail, three more samples are collected and tested. If those fail the company is reported to UKASTA.

"Ideally we would like to collect more samples, but this level is a good balance that is affordable, practical and effective," says Dr Moore.

But he points out that the independent testing of samples at ADAS is only part of the scheme. Each additive manufacturer has submitted details of product quality control procedures and testing during additive manufacture. When necessary additive companies were told to improve their in-house quality control and testing.

"Every batch of additive is checked in-house."


&#8226 Keep inoculants in a cool, dark shed, away from sunlight.

&#8226 Refrigerate if storing for extended periods.

&#8226 Check the use-by date.

&#8226 Follow handling instructions.

The onus is on the manufacturer, to make a product which will work under farm conditions and to ensure sufficient advice is available on storage.

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