15 January 1999

Liquid feed diet goes on trial as AGP alternative

Young pigs could drink their

way to good health using

fermented liquid feed to

replace feed treated with

antibiotic growth promoters.

Simon Wragg reports

THE recent ban on four major antibiotic growth promoters (AGPs) on the grounds of potential risks to human health is causing concern among pig producers, many of whom believe a total ban on AGPs will follow.

Should this happen, researchers in Devon believe fermented liquid feed could replace AGPs in pig diets and have just been awarded a £400,000 grant to help produce inoculants. They may also develop a feeding blueprint for this system.

Peter Brooks, who heads the animal production research team at University of Plymouths Seale Hayne faculty of agriculture, is adamant that an alternative to AGPs must be found quickly. Bacterias ability to mutate and develop resistance to anti-microbials, the cost and lengthy procedure of product licensing, and banning of some AGPs are key concerns.

So why does he believe fermented liquid feed could replace AGPs? "If you look at sows milk it is fermented naturally with lactic acid bacteria, delivered at regular intervals and contains the right nutrients and bacteria for healthy development of suckling pigs. Fermented liquid feed can replicate these properties."

Performance dip

In doing so, fermented liquid feed could remove the post-weaning performance dip associated with a sudden change in diet – switching from sows milk at 20% DM to dry pelleted feed at 85% DM – and eating behaviour when moving from restricted to ad-lib feeding. "It can take a fortnight to recover the fall in growth rate. Even after recovery, piglets rarely overcome the lapse in days to finishing."

Research has also shown that fermenting liquid feed can boost piglet performance to a greater extent than AGPs. Typically, AGPs contribute a 2-3% increase in performance – although some studies have found increases of 10% plus – while fermented liquid feed could improve performance by 15-20%, says Prof Brooks.

The fundamental drawback to fermented liquid feed is the exclusion of in-feed therapeutic antibiotics. "Clearly, these are anti-microbials and so would kill off beneficial bacteria, although effects differ by product. They can also sig- nificantly affect pH of the liquid"

This means alternative medication strategies must be considered, including water-soluble medication.

So how does fermented liquid feeding work? The system incorporates a large tank of warm liquid feed in which useful bacteria – introduced by the inoculant – are cultured. Typically, fermenting liquid must be kept above 15 degrees C if bacteria are to multiply. Below this temperature yeasts form, which can be detrimental to fermentation. "This requires the feed delivery system to be insulated," Prof Brooks says.

As some of the feed is piped into troughs the remaining liquid is topped up. Left to allow bacteria to multiply in the new liquid, the whole system takes on the guise of a living organism. "Thats the problem: Producers must be capable of managing a living feed system," he says.

Already a small number of specialist producers use it, he says. But the relatively small pool of expertise to develop and manage these systems to give consistent results and cost of equipment has limited its use.

He can list a catalogue of disasters which have happened with these systems. "Its not unknown for producers to top up tanks with cold water which kills off the bacteria. Another problem is keeping the feed too long," he says.

The Seale Hayne research – funded by MAFF, MLC and a consortium of liquid feeders – should overcome these difficulties. Work on developing about 50 inoculants to be used commercially in fermented liquid diets using various ingredients, and possibly also creating a management blueprint, is expected to be completed in two years.

Although some inoculants are already available, Prof Brooks believes that refining these and developing more will allow producers to choose products which suit the feed ingredients used and will produce consistent results. Acids, which also make liquid feed more acceptable to the piglets gut, have been considered as an alternative but cost £70/t of feed treated compared with £7/t of feed treated for inoculants.

Producing consistent feed at minimum cost means systems must be designed to reduce the volume and hence the length of time liquid is left fermenting to repopulate bacteria. "Drawing off liquid frequently in small volumes could be a solution," he says.

So who will benefit from fermenting liquid feed? "Large scale weaner producers stand to gain most from fermenting liquid feed, especially where all-in/all-out systems operate, minimising the level of equipment.

"But theres no reason why smaller producers shouldnt adopt the system. If capital cost of an automated system is prohibitive, theres no reason why basic equipment cannot be used," he suggests.

But he says that finishers may find costs prohibitive given the practicalities of having tanks large enough for high volumes of feed – typically two days worth at a time.

Steve Stokes, of Hampshire Feeding Systems, says the costs for installing systems for fermented liquid feed range from £9.50/pig space for single diet and up to £15.40/pig space for multi-diet systems. These costs are based on a unit producing 200 pigs/week with accommodation for 1000 weaners and do not include installation costs.

Prof Brooks says that there is no reason why more producers cannot begin adopting this system, but being relatively new, there are few nutritionists and advisers who have sufficient knowledge of fermented liquid feed to provide support, he warns.

"It could take 12 months to get to grips with fermenting liquid feed – but were in the same position as we were with silage inoculants 20 years ago."

As a serious suggestion he advises producers considering fermented liquid feed to try home wine-making first. "It requires the same principles and need for disciplined management," he says. &#42

FERMENTEDLIQUIDFEED

&#8226 Could replace AGPs.

&#8226 No dip in weaner growth.

&#8226 High capital cost.

&#8226 Strict management vital.