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Functional Additives
Thursday, May 12, 2016 10:01:10 PM
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Feed preservation with organic acids - a way to achieve safe feed sustainably

 

Christian Lückstädt, ADDCON GmbH, Bonn, Germany

          

  

Supplying the world population with sufficient food is more important challenge today than it has ever been. Economic development brings with it different demands for food producers, increasing the pressure on livestock producers to produce sufficient, safe protein sources for human consumption efficiently and sustainably (Kochannek, 2011). On a global scale, reducing food and feed waste, which represents up to 50% of the 4 billion tonnes of food production every year, according to the IMECHE-report (2013), may be one way to help us rise to the challenge.

 

Feed or raw material wastage during storage happens world-wide, but differs in its nature and development due to climate conditions. In a developed country such as Australia, wastage of up to 0.75% in grain is the maximum which may still be tolerated, whereas in Ghana up to 50% may be experienced. India and Pakistan on the other hand will lose annually 21 and 3.2 million tonnes of feed raw materials, respectively (IMECHE, 2013).

 

The potential applications of organic acids in livestock nutrition and feed preservation have been known for decades and are documented by many scientific studies. Acids make a fundamental contribution to feed hygiene, since they suppress the growth of mould and thus restrict the potential production and detrimental effects of mycotoxins. Furthermore, bacterial degradation of the feed is inhibited. Consequently, the feed's safety is guaranteed by adding organic acids and can secure healthy animals, good animal performance and safeguard overall economic animal production.

 

The efficacy of different organic acids for microorganism growth inhibition can be compared using their minimum inhibitory concentration (MIC, Table 1).

 

Table 1: Minimum inhibition concentration of different acids against various microorganisms (%) - modified after Sava, 2011

 
 

Formic Acid

Propionic Acid

Sorbic Acid

Benzoic Acid

 

Aspergillus flavus

0.50

0.25

0.45

0.50

 

Cladosporium sp.

0.50

0.25

0.50

0.50

 

Staphylococcus aureus

0.13

0.25

0.75

0.85

 

Escherichia coli

0.10

0.50

0.75

0.70

 

Candida albicans

0.25

0.50

0.20

0.50

 

Propionic acid has a broad efficacy and is the most efficacious of the organic acids against fungi. On the other hand, formic acid is more efficacious against bacteria (Coelho, 1990), while Lück and Jager (1995) described benzoic acid to be highly effective against yeast. The antimicrobial effects of organic acids in feed and their minimum inhibition concentrations are reviewed in detail elsewhere (Singh-Verma, 1973; Strauss and Hayler, 2001).

 

Even in a hygienic environment, feed can be infected to a certain degree with fungi, bacteria or yeast. Peisker (2011) demonstrated that there is a typical recontamination pattern during the journey from the feed plant after pelleting to the farm silo (Figure 1), especially when no chemical stabilizer, such as an organic acid, is added.

 


 

Figure 1: Recontamination pattern from feed mill to farm silo with bacteria without acidifier – modified after Peisker 2011

 

Successful preservative products need to guarantee the preservation and stabilisation of feed, while offering easy, user-friendly handling to the customer. This need formed the impetus behind feed preservation trials in Germany, which were carried out with a non-corrosive premixture of propionic acid and its salt with benzoic acid (Kofa® Feed).

 

A series of preservation trials were carried out under standardized conditions at the Chamber of Agriculture in Lower-Saxony, Germany. Different commercially available compound feeds, obtained from pig and poultry farms, were used for the trials. In order to mimic natural microbial infection, the feed samples were blended with 10% cereal waste. The moisture content of the feed was kept at 15%. Prepared feed was treated with different concentrations (1, 3, 5 and 10 kg/t) of Kofa® Feed (premixture of propionic acid, sodium propionate, benzoic acid) and stored for 28 days under aerobic conditions in an incubator at ambient temperature (25°C). Relative humidity was kept stable at 80%. The storage length of 4 weeks was chosen because compound feed is usually not stored longer than this. The microbial tests after the trial were done at LUFA in Oldenburg and followed the procedures described by Bucher and Thalmann – EFMO (2006). All determinations were done in triplicate. Data were subjected to statistical analysis and a significance level of 0.05 was used in all tests. The data displayed in the figures are mean values.

 

Results under challenge conditions (constantly high relative humidity, high moisture content of feed) as well as a high initial microbial contamination revealed that a non-corrosive combination of propionic acid, its sodium salt and benzoic acid (Kofa® Feed; afterwards referred to as "NC preservative" is able to inhibit the growth of spoilage indicating bacteria and moulds highly significantly (P<0.001), as well as that of yeast in poultry and pig feed.

 


 

Figure 2: Reduction of yeast (log CFU/g) in layer feed stored with or without NC-preservative for 28 days (P<0.001)

 

Figure 2 shows the highly significant impact of the NC-preservative against yeast. Inclusion of 1 kg/t of the product resulted in a significant reduction of yeast by 98%, while the higher doses achieved a significant >7 log reduction (or a reduction by 100%) of yeast in the layer feed.

 


 

Figure 3: Reduction in spoilage indicating moulds (log CFU/g) in pig feed stored with or without NC-preservative for 28 days (P<0.001)

 

The use of 1 kg/t NC-preservative resulted in a significant >3 log reduction (or a reduction by 99.95%) of moulds in the stored feed for fatteners (Figure 3).

 


 

Figure 4: Reduction in spoilage indicating bacteria (log CFU/g) in layer feed stored with or without NC-preservative for 28 days (P<0.001)

 

Finally, as shown in Figure 4, the use of 1 kg/t of Kofa® Feed resulted in a reduction of spoilage-indicating bacteria by 85%, while the use of 3 kg/t of the product showed a significant 3 log reduction (or a reduction by 99.9%) of bacteria in the stored layer feed.

 

Many experts consider mould counts of 106 CFU/g as high, and expect a negative impact on the animal fed with such a feed (e.g. Manitoba Agriculture, Food and Rural Development). Furthermore, it is generally accepted that spoilage becomes organoleptically detectable at bacterial levels of 108 CFU/g (Doyle et al., 1997). However, the impact on the animal begins at significantly lower counts. Most often, intoxication requires that the toxin producing bacteria have grown to high numbers (105 - 108 CFU/g) in the feed before it is eaten, however the minimal infective dosage, MID, varies considerably between species (FAO). Therefore, it is widely recommended that Salmonella should be absent in 25 g of sampled material. Because of this variation, general guidelines for a bacterial load limit in animal feed are missing. According to Smith (2007) the amount of processed feed ingredients with an Enterobacter count of 105 CFU/g make up a majority of tested samples – thus it can be assumed that the overall bacterial level will be a magnitude higher. Any reduction in such high numbers with the aid of organic acids will therefore further lead to improved safety - for the animal as well as for the human consumer.

 

It has been shown in a wide range of trials that the combination of ingredients in Kofa® Feed is able to have a significant impact at dosage levels between 1 and 3 kg/t against bacteria, moulds and yeast in compound feed for various species. As such, Kofa® Feed can play a vital role in achieving a state of biosecurity.

   

 

For more of the article, please click here.

 

Article made possible through the contribution of Christian Lückstädt and ADDCON GmbH

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