2. What is bacterial/microbial inhibition?
First, we will look at what makes bacteria, moulds and yeast grow. Other microorganisms like parasites, protozoa and viruses are also present in the food and feed industry but will often have more complex mechanisms and are not covered here.
There are several factors affecting microbial growth:
- The matrix of the feed (a source of nutrients for the bacteria to grow on),
- The acidity of the feed material - depending on the pH, the bacteria, mould and yeasts will have favourable/non-favourable conditions to grow on
- Temperature- and moisture levels will also influence the magnitude of growth.
- Microbial growth can occur either under aerobic or anaerobic conditions; i.e., with or without oxygen. Depending on the microorganism, this will impact growth either positively or negatively.
- Time is also relevant and will impact potential colonisation of bacterial cells and, hence, the magnitude of growth.
Microbial growth can be controlled either by prevention or inhibition – using an antimicrobial agent.
8. How do acidifiers work?
Organic acids have two functions as antimicrobial agents. Their primary antimicrobial action is through pH depression. In addition, the ability of the organic acids to change from undissociated to dissociated form, depending on the environmental pH, makes them effective antimicrobial agents. An acid in the undissociated form can freely diffuse through the semipermeable cell wall of the microorganism into their cell cytoplasm (Figure 2).
Once inside the cell, where the pH is maintained near 7, the acid will dissociate: The H+ ion releases and as a result the pH will decrease. A change in pH will suppress cell enzymes and nutrient transport systems (Lueck, 1980).
9. What are the costs and benefits of using an acidifier?
Fefana has highlighted several aspects of using organic acids in the animal feed sector:
“Between 50 and 80% of the total cost of poultry and pig production in Europe relate to feed. Therefore, it makes sense to improve the efficiency of turning feed into animal growth.
In Germany, the largest economy in the EU, more than 70 kg of pork and poultry are consumed per capita per year, showing the scale of the need to improve feed efficiency, cost of production and environmental impact. Controlling the balance of the intestinal microbiota is the foundation of a profitable modern livestock operation. The maintenance of a stable microflora within the digestive tract is a key aspect in achieving optimal feed efficiency; it also impacts food safety and animal welfare. A holo-analysis of organic acids’ use in pig nutrition has revealed that feed efficiency (Feed Conversion Ratio, FCR) can be improved by an average of 3.7%. Assuming an overall FCR of 2.2 from the piglet to the fattener and a slaughter weight of 100 kg, this average improvement of feed efficiency of 3.7% would result in a saving of 8 kg feed per pig.
Comparable calculations could be applied to poultry production, which is expected to become the largest source of meat worldwide in the next few years. In a trial with broilers using a granulated premixture including benzoic acid, an improvement in FCR from 1.89 to 1.81 resulted in a feed saving of 180 g/bird.
Similar results with protected acids are expected in aqua culture, which is currently the fastest growing meat production sector worldwide. The use of organic acids for sanitizing feed or water can reduce mortality on the farm and thereby improve the overall efficiency of feed use and production cost.“
Between 50 and 80% of the total cost of poultry and pig production in Europe relate to feed.
Acidifiers are very useful when there is a microbial imbalance and conditions are challenging. In some cases, their use is even critical.
There is a diversity of needs and, hence, a corresponding variety of microbial inhibitors available. Animal welfare, sustainability and cost versus performance for microbial inhibition are some of the decisive factors to consider when choosing an acidifier.