• In the feedmill, formic acid is now classified as a bacterial decontaminating agent (including, but not limited to Salmonella) to improve feed hygiene (Feed Additive Register 2017/940).
  • pHorce helps control levels of potentially harmful bacteria that may be present in fish meal which can impair animal performance.
  • pHorce is part of Anpario’s Acid Based Eubiotics (ABE) range and is a concentrated blend of pure liquid formic and propionic acids on a unique mineral carrier delivery system; chosen to ensure maximum efficacy during feed manufacture and throughout the gastrointestinal tract (GIT).
  • This trial was conducted to assess the level of Salmonella inhibition in fish meal.

The moisture content of a sample of fishmeal was determined and the sample was then sterilised by the addition of steam to ensure that there were no indigenous bacteria in the sample, and allowed to cool. The moisture content was again determined and readjusted to its original level (by oven drying). The fishmeal was mixed thoroughly using a laboratory roller. 50 replicates of 400g aliquots of fishmeal were allocated to 7 treatment groups in a 7x7x6 experimental design (table 1). Each of sample were inoculated with a diluted sample of a specific Salmonella serotype culture isolated from naturally contaminated feed with the exception of S. cerro, which was purchased from external sources. Three 10g samples from each treatment were analysed for Salmonella colony forming units (cfu) on day 1, 2, 3, 7, 14, 21 and 28.

Treatment 1 (NC) 2 3 4 5 6 7
pHorce (kg/t) 0 5 10 15 20 25 30

Table 1. Sample number and pHorce content in each sample.

To study the effect of moisture content on the survival of Salmonella in treated meal 2 aliquots of 400g were given additional moisture contents of approximately 2% and 5% above the initial level. These samples were mixed in the same way as described above to ensure even distribution and the moisture contents of the samples were measured. The samples were allocated to 7 treatment groups in a 7×7 experimental design (table 1). S. seftenberg was chosen as the test organism for this trial as it showed more resistance to pHorce treatments in previous tests. Three 10g samples from each treatment were analysed for S. seftenberg colony forming units (cfu) on day 1, 2, 3, 7, 14, 21 and 28.

  • During the experiment Salmonella numbers in the control samples increased by between 50 and 100%.
  • The kill rate of Salmonella at normal moisture content is slow. This is because the water activity of the medium is too low to support active microbial metabolism and it is the excretion of hydrogen ions that leads to cell death. However a low level of Salmonella multiplication was seen to occur at these low water activities.
  • Naturally occurring fish oils have a protective effect on the bacterial cells helping to prevent the monomeric vapours from crossing the cell membrane.
  • pHorce does provide a very rapid reduction in Salmonellae numbers with a 24 hour kill of Salmonellae in Fishmeal as follows:
    • Group B Salmonellae 1% at 5kg/t (Fig. 1)
    • Group C Salmonellae 4% at 5kg/t (Fig. 2 and 3)
    • Group E Salmonellae 4% at 5kg/t (Fig. 4 and 5)
    • Group K Salmonellae 8% at 5kg/t (Fig. 6)
  • Under normal conditions (using 25kg/t pHorce) effective decontamination (represented as 95% kill rate) can be achieved at
    • 14 days for Group B Salmonella (Fig. 1)
    • 21 days for Group C (Fig. 2 and 3) and E Salmonella (Fig. 4 and 5)
    • Group K Salmonellae show a higher acid tolerance and require 30kg/t for 28 days (Fig. 6)
  • With additional moisture, the kill rate is accelerated and Group E Salmonellae achieved a 95% kill rate (less than 5% surviving cfu) 7 days earlier/or at the same time but at 5kg/t (Fig 7 and 8). The addition of moisture to fishmeal may accelerate kill rate if rapid decontamination is required.
  • pHorce is also as a preservative at low concentrations so adding pHorce to fishmeal prior to shipment or storage can help to prevent colonisation and multiplication of Salmonellae. pHorce can help protect the fishmeal in areas where condensation elevates moisture levels and allows Salmonella numbers to increase.
  • pHorce is a feed additive that may enhance feed conversion in both pigs and poultry, the addition of pHorce to fishmeal has both decontamination and potential animal performance benefits.