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Scott Faul, director Asia Pacific for Anitox corp— Controlling Salmonella in pigs will require a legislative and economic push on feed-manufacturers, pig producers and meat processors to implement the increased surveillance and multiple interventions required.
The Asia-Pacific pig industry is feeling the pressure as Western-style feed and food standards are impacting and pushing producers and feed manufacturers to improve performance.
Despite increasing standards, there is still much that Asia-Pacific pig producers and others involved in the food sector can learn from what has been happening in highly-developed markets like Europe where, despite stringent regulations, food safety is still a major issue.
Feed-related incidents During the past three years, a number of entirely preventable feed-related incidents throughout the world have highlighted the direct impact contaminated feed can have on meat production. Such incidents ultimately lead to greater intervention by the regulatory authorities in the form of increased feed and food safety policies to regulate, control and implement regulations to prevent food-borne diseases such as Salmonellosis, Shigellosis, Campylobacteriosis, Listeriosis and Vibrio parahaemolyticus.
Untreated feed is one of the key ways to introduce Salmonella and other pathogens onto pig farms, and subsequently into the food chain. Clearly a key element in effective control measures is to ensure that feed is pathogen-free up to the point of consumption.
Many feed-related incidents can easily be prevented by implementing well-proven technologies, for example, treating all feed materials and finished feeds with an effective, approved biocide to eliminate pathogens.
Feed safety awarenessAlthough awareness of feed safety issues by consumers and government is increasing in the Asia Pacific, there is a lack of strong policy solutions to control bacterial zoonotics in primary production. This is partly because responsibility for feed and food safety policy falls to different governmental bodies in different countries.
In Singapore, for example, the manufacture, import and sale of food products are governed by the Sale of Food Act 2002, while the Food Regulations 2006 are administered by the Agri-Food and Veterinary Authority of Singapore, the country’s national food safety authority. In Taiwan, the Department of Health is the statutory body responsible for the management of food safety and the Thailand FDA is the principal department of the Ministry of Public Health in charge of consumer safety in the consumption of food.
The consequence of relative insufficiency in policy solutions for controlling bacterial zoonotics in primary production across Asia Pacific is that much of the responsibility for eliminating bacterial contaminants in meat still rests with consumers by ensuring that food is thoroughly cooked. Significantly, however, this approach fails to take into account any cross-contamination issues during food storage and preparation.
The inevitable result of neglecting to implement available food safety technologies to eliminate pathogenic microorganisms at sites of primary production will be instances of unsafe food products being produced. It is important to stress that food hygiene and safety can only be assured if all the precautionary and preventative measures are taken throughout the entire production and distribution process. This extends from the early stage of proper handling of feed raw materials and food ingredients throughout the various stages of production.
European feed, food safetyEurope has been the driving force behind feed and food safety legislation for many years, and given the large, increasing pig populations which now exist throughout Asia Pacific, including significant numbers in China, Korea, Taiwan and Vietnam, the region can learn from that region’s experiences.
The European Union regulatory authority, the European Food Standards Agency (EFSA), already has a rigorous program to monitor and eliminate zoonotic pathogens, specifically Salmonella Enteritidis and Salmonella Typhimurium, in meat, starting at source on primary production units.
Zoonoses-focused legislation, such as the Control of Salmonella and Other Specified Food Borne Zoonotic Agents Regulation (2160/2003), is well-established and requires all pig farmers to implement procedures to ensure that feed is free from Salmonella.
Salmonella, pig feed And the EFSA is increasingly turning its attention to pigs, as it estimates that 10 percent to 20 percent of human cases of Salmonellosis that occur within the EU can be attributed to the consumption of pig meat.
Salmonella infections in pigs are largely asymptomatic, with a high proportion of infected pigs becoming carriers and intermittent execrators of Salmonella in their feces. Preventing the contamination of farms with viable and persistent Salmonella exposures from outwardly “healthy” carrier pigs is difficult to achieve.
The link between feed, farm and food is well recognized and separate studies in a variety of domestic animals have clearly demonstrated that Salmonella isolated from the feed mill or the finished feed can be later isolated from the farm, meat processing plant, eggs or meat (Shirota et al., 2001, Liebana et al., 2002, Österberg et al., 2006, Molla et al., 2010).
In countries with a low on-farm prevalence of Salmonella, human infections linked to pork consumption have been traced back to Salmonella-contaminated feedstuffs (Hald et al., 2006, Wierup et al., 2010). As other countries, including those in Asia Pacific, reduce their Salmonella incidence, they too will have to become ever more vigilant in terms of producing ‘Salmonella-free’ feedstuffs for their pigs.
Heat treatment has traditionally been used to contain the problem. However, this process adds significantly to the cost of feed, is energy-intensive, has a high ‘carbon footprint’, can damage vitamins/nutrients, may not kill all pathogens and has no residual effect. To be confident of eliminating 100 percent of Salmonella in feed (including heat-tolerant strains), the meal must be heated to >85°C for at least four minutes and contain 14.5 percent to 15 percent moisture. Unfortunately, the majority of mills are unable to achieving anything like these conditions and even when using feed hygenizers, finished “clean” feed must still be cooled, stored and distributed, thus, exposing it to the risk of re-contamination.
Salmonella contamination can all too easily occur at these stages and pigs are then exposed to Salmonella-contaminated feed. Therefore, unless other measures are implemented, re-contamination can occur in the mill, during transport or on farm, so it is critical to ensure the feed is treated effectively to prevent this.
Organic acids and their salts are also popular Salmonella-control products in pig feed. There are, however, significant limitations to their effectiveness in-feed. To kill Salmonella they need to penetrate the bacteria and this requires the molecule to be un-dissociated; generally requiring low pH, conditions typically not found in feed but in pigs’ stomach acid. It is within the pig that organic acids exert their greatest anti-Salmonella effects; arguably too little, too late for some pigs.
A recent independent study has demonstrated that organic acid-treated samples often show-up as Salmonella-negative, despite actually containing viable Salmonella (Carrique-Mas et al., 2006). Such masking of Salmonella (in effect, false-negatives) is potentially catastrophic for both feed-manufacturer and pig producer – the feed-manufacturer risks contaminating the mill and the feed, while the pig producer risks infecting their pigs with Salmonella.
For many organic acids and blends, high inclusion levels are required to provide effective in-feed Salmonella control.
Clean pig feed Looking at the poultry industry, where Salmonella control has largely been a success; we find that the most popular in-feed Salmonella control products are products such as Termin-8. Containing a synergistic combination of anti-microbial substances, surfactant and propionic acid; it provides rapid, persistent and non-pH-dependant anti-Salmonella activity.
Research by the EFSA found that a formaldehyde-based feed treatment provides a more effective, cost-efficient alternative to heat treatment and, crucially, has a residual protective effect. This was confirmed by Britain’s Defra-funded research at the Veterinary Laboratories Agency which investigated the efficacy of organic acids and formaldehyde treatments on animal feeds. Its investigations showed that the treatment which achieved by far the best kill of Salmonella in feed, rather than just ‘masking’ the problem, was a liquid antimicrobial bactericide product containing 33 percent formaldehyde, propionic acid and natural terpenes, a formula identical to Termin-8, which Anitox developed to reduce mould and bacteria in feed and feed ingredients.
Controlling Salmonella in pigs will require a legislative and economic push on feed-manufacturers, pig producers and meat processors to implement the increased surveillance and multiple interventions required. As these interventions take effect, the need to ensure that pigs are fed ‘Salmonella-free’ feed will become ever more important. As feed-manufacturers and pig producers seek the most effective ways to produce Salmonella-free feed they might be wise to look to the successes achieved by the poultry industry and the methods it used.
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