Organic acids or as they are sometime called short chain fatty acids, are used in animal feed for many years. They have proven to be excellent ingredients especially in the prevention of gram negative pathogenic bacteria. Controlling programs forÂ enterobacteriae, Escherichia coli and Salmonella often make use of organic acids.
When comparing the use for different species, it is noted that the use in poultry diets is less than for some other species. This article focusses on the use in poultry and why differences can occur.
Organic acids physical appearance:
Organic acids in their pure form can be present as dry powders (citric acid, fumaric acid) or as liquids (formic acid, lactic acid). Liquids are less easy to work with in general for feed processors. Therefore for the liquid organic acids, often their salts are used. Especially the calcium salts, like calcium formate, are well known in feed. Â But alternatively, the liquid organic acids can also be brought onto carriers like silicates. This creates dry powders for the application, while active ingredients stay liquid.
Organic acids and their properties:
The two most important reasons for using organic acids in feeds are most likely:
- The effect of organic acids on pH
- The effect of organic acids against pathogenic bacteria.
The first effect, lowering the pH value, can be achieved by:
- lowering the pH of the feed itself,
- lowering the buffer capacity of the feed.
A lower buffer capacity of the feed means that the animal needs less acid secretion by itself, in order to establish the low pH value in the stomach/gizzard.
The effect of organic acids on the pH value itself differ, but all acids have their influence on the pH values. The pure acids mainly have their effect directly on the pH value, while the calcium salts mainly have an effect via lowering the buffer capacity of feed. Although there are differences between different products, all products will have more / less effect on the pH.
The antibacterial properties of organic acids differ quite a bit. The calcium salts of organic acids first need transformation from the calcium salt into the pure acid, before they are really antibacterial. This happens under low pH conditions (stomach/gizzard) and means that the antibacterial effect of the salts is only present during the retention time of the feed in the stomach/gizzard.
Some other organic acids, like fumaric acid and citric acid have no direct antibacterial properties at all.
And last but not least we have a group of organic acids like formic and lactic acid, that have strong antibacterial properties on itself. When we compare the antibacterial effect of these acids, we see that formic acid for instance is extra strong against Salmonella and lactic acid against Escherichia coli. It is beyond the scope of this summary to go into the detailed antibacterial action of the different organic acids.
Organic acids in poultry:
For poultry, the effect of organic acids is mainly the effect against pathogenic bacteria as chickens in general have less problems in creating a low pH value in the stomach/gizzard compared with other species. Therefore it is important to make a correct selection of organic acid formulas before application in poultry.
The acid salts have less antibacterial power and acids like citric acid and fumaric acid have no antibacterial power at all. Chances to have a positive effect on performance for products based on these ingredients are therefore more limited.
Effective acids against pathogenic bacteria for poultry are lactic acid, formic acid and benzoic acid for instance. Formulas using these ingredients in general help the animal to withstand pathogenic pressure. By reducing the number of pathogenic bacteria a more healthy microflora is stimulated and animal performance can increase.
Dosage rate in poultry feed
Also dosage rate of organic acids in poultry feed needs carefull consideration. Poultry is more susceptible for a high dosage of free acids like formic acid and lactic acid. While other species easily accept dosage rates of 10 kg / ton and more,Â the oesophagus of poultry can more easily get irritated by such dosage rates. Irritation leads to reduced feed intake and thereby reduced performance. Therefore it is recommendable to dose free acids like formic acid and lactic acid only in limited amounts (up to 4kg/ton) to poultry feed.
Organic acids / Short Chain Fatty Acids are known in feeds mainly because of their effect on pH and against pathogenic bacterial. For poultry the effect against pathogenic bacteria is more important than the effect on pH. The main function of calcium salts of organic acids and acids like citric and fumaric acid is their effect on pH and these ingredients are less attractive for poultry acidification. Antibacterial acidsÂ like formic and lactic acid have good antibacterial spectrum against important poultry pathogens like Salmonella and Escherichia Coli. These acids are liquid, but when on silica carrier, they can become very interesting formulas to stimulate poultry performance by their action against undesired micro flora.