Food quality - Organic Agriculture: A Global Perspective - page 311

composting materials at a temperature of between 131°F (55°C) and 170°F (77°C)
for 3 days. Producers using a windrow system must maintain the composting
materials at a temperature between 131°F (55°C) and 170°F (77°C) for 15 days,
during which time, the materials must be turned a minimum of five times.
Organic farmers tend to think that their production methods keep the animals and soils so
healthy that any zoonotic pathogens introduced from other farms or wild animals are quickly
eliminated through natural protection mechanisms. Surveys and comparisons reviewed by
Korba (2003), BMVEL (2003) and Bourn and Prescott (2003) concluded that the microbiologi-
cal risk from organic foods is smaller or similar to corresponding conventional foods, even
though pathogens are able to survive for extended periods in stored manure. The information
tends to be based on surprisingly few studies often of rather low information value. For
example, a report is cited in Korba et al . (2003) to 'show that, compared to conventional agri-
culture, organic production leads to a higher Salmonella contamination in eggs, poultry meat
and pork meat'. In the report, which was not peer-reviewed (European Union 2001), this con-
clusion refers to the statement 'in comparison with conventional farming, more cases of sal-
monella in eggs, poultry and pig meat have been registered', without any figures, author
identification or other information that allows tracking of the source in order to define the
year and geographical area to which it referred. A recent initiative by a Dutch research group
aims to understand and control the factors that determine the pathogen transmission risk in
the entire organic vegetable production chain, from the feeding regime of the cows to the post-
harvest treatment of the vegetables (Franz et al . 2003).
A few studies hint at some of the reasons for the absence of predicted risks, and indicate
that organic food may be safer than estimated. Hald et al . (1999) suggested that if organic farm
animals tend to be exposed to zoonotic pathogens like Salmonella at an early age and then
become so resistant that the infections are eliminated before slaughter, the pathogen load will
be systematically overestimated if testing is done by measuring antibodies in the animal tissues
rather than actual presence of the pathogen in faeces. An ongoing study in the EU-project
QualityLowInputFood (QLIF 2006), is testing this hypothesis by comparing antibodies in
meat samples and bacteria in faeces in organic and conventional pigs from defined outdoor
and indoor farming systems (M.K. Bonde pers. comm.). Some studies indicate that the more
extensive use of grass and other roughage in organic animal production improves the ability of
the animals to eliminate zoonotic pathogens (Couzin 1998, Diez-Gonzalez et al . 1998).
Another aspect of the issue of zoonotic pathogens in organic animals is that out of necessity,
organic farmers have to give high preference to good health characteristics when selecting
breeding stock, since it is more difficult or impossible to control health problems by antibiot-
ics. In the USA, where a total ban on the use of antibiotics for organic cattle has forced milk
farmers to select heavily for highly resistant stock, some organic farmers have now started
selling their surplus heifers to conventional farmers at a premium price, since even in a con-
ventional system, genetic resistance is more effective than antibiotic treatment in keeping
animals healthy (J. Riddle pers. comm., 2005). Although no studies on the impact of animal
genetic resistance on food safety have been reported, this is an aspect that should be investi-
gated in future research. It is also an example of how organic production system developments
can directly benefit conventional producers.
Regarding pathogen transfer from manure to vegetables, several studies have failed to show
measurable contamination of the final product when Salmonella or Escherichia coli O157:H7
were deliberately introduced into lettuce growing systems (Johannessen et al . 2004, U. Köpke
pers. comm., 2005). Studies in the Netherlands (Franz et al . 2005) highlight two important
components of this elimination: first, the numbers of pathogens (added by inoculation) fell