16 April 1999

What to use after AGPs

What can producers use to

protect pig growth when

antimicrobial growth

promoter use is restricted?

Former MLC Stotfold

manager Paul Blanchard

looks at the options.

Simon Wragg reports

ONLY 70% of the genetic potential of UK pigs is achieved on-farm from current management practices including use of antimicrobial growth promoters (AGPs) and that could fall if effective alternatives to AGPs are not found.

Use of tylosin, zinc bacitracin and virginiamycin will be suspended from July this year. Olaquindox will follow from September, leaving avilamycin, salinomycin and flavomycin to an uncertain future. But the producers armoury to support production is still well stocked, albeit with a number of unfamiliar products.

According to former MLC Stotfold pig unit manager Paul Blanchard – now working for Derbyshire feed supplement supplier Frank Wright – producers have come to rely on AGPs to offset the impact of unit health and management on output.

There are two reasons behind the reliance, says Dr Blanchard. "The UK herd health status has deteriorated over time, particularly since the arrival of Blue Ear – PRRS – and swine influenza. Combined with a lack of investment in buildings and greater extensification we now see more pigs kept in conditions far removed from the ideal controlled environment once achieved on-farm."

To compensate for the lack of control, AGP use has risen, giving significant saving in production costs. Their use is suggested to increase daily liveweight gain by 4%, feed conversion by 3.2% and feed intake by almost 1%. The increased margin achieved from better feed conversion is worth on average 60p a pig on its own at todays prices, says Dr Blanchard.

With further restrictions on AGP use likely, should producers quickly select one of the many alternative products on the market? Dr Blanchard says a review of unit management should be a higher priority, finding ways of improving pig health. This could include vaccination programmes and change of management practices, for example a move from continuous flow to all-in, all-out systems.

"Once we have considered how pigs will be managed we can decide how to feed them," explains Dr Blanchard. "Use of digestive enhancers – as alternatives to AGPs – should be seen as the icing on the cake, not as a basic raw material."

There are several options to consider, including continued use of one of the AGPs still in circulation. These have been shown in trials to improve growth and feed efficiency particularly in starter and grower diets. The cost of each option is evaluated regularly and current figures are available (see table).

But these cannot always be compared with the value of growth benefit they provide as many newer alternative products lack independent assessment, he adds.

Despite this, a review of the main AGP alternative products is possible. Where health status is not a limiting factor, and high levels of cereals are used, consider using a feed enzyme. This will improve digestibility of cereal-based feed by breaking down cereal cell walls, and can increase feed use efficiency, particularly in home mixed mash rations. Feed enzymes are not resistant to high temperatures, and can be less effective in pelleted rations, he warns.

Organic acids form another group and can be used to improve output by supporting pig health. Acid products help preserve feed, reducing levels of mould, toxins and bacteria. The lower the level of these anti-nutrient factors, the healthier a pigs gut remains. This can improve feed intake and lead to faster growth. While organic acids are stable when heated, they take up space within feeds, typically up to 10kg/t in creep and 3kg/t in grower diets, reducing inclusion of other ingredients in the ration make-up, he suggests.

Probiotics – often referred to as microbial feed additives – are seen as an environmental alternative to AGPs. These are used to generate the correct bacteria in a pigs gut to break down feed. The bacteria multiply rapidly, fermenting carbohydrates to produce lactic acid. Increased acidity in the gut inhibits growth of potentially harmful bacteria.

"Benefits from these are dependant on what bugs are already on-farm, and they cannot be used with AGPs or products with antimicrobial action which will destroy them," says Dr Blanchard.

Digestive yeasts form a new group of products which encourage secretion of digestive enzymes in the gut and lactic acid production. Like probiotics they improve the ratio of beneficial bacteria compared with pathogenic bacteria. "Some can be susceptible to heat, so products must be matched to likely heat treatment of feed."

Essential oils are another new group of alternatives. Used alone or in a mix, these oils are thought to increase digestive enzyme production and regulate gut microflora to provide a healthier gut environment.

"This list is not exhaustive. There are a number of alternatives appearing on the market including protected sugars, plant extracts and spices. Producers should not ignore these, but they lack the independent research required for AGP approval. Independent research would increase our understanding and confidence when deciding where to use these products," says Dr Blanchard. &#42

Typical cost of options

for 7-90kg (p/pig)

Tylosin* 40

Avilamycin 50

Enzymes 25-50

Organic acids 40

Probiotics 60

Yeast (young pigs only) 10

Essential oils 50

*Tylosin banned from July 1, 1999