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Benefi ts of Organic Acids on Piglet Gut Health

By Heidi Hall, Technical Manager Swine, Anpario

The piglet digestive system is immature at weaning and it is also further negatively affected through intake depression, dietary changes, novel ingredients and the stress of new litter mates and environment. Therefore, maximising piglet health prior to weaning and ensuring the feed pre and post weaning is of high quality and consistency is a necessity. Organic acids (OA) have been used for a number of years in animal

production, historically in liquid form as water conditioners and more recently, as feed additives in either protected or buffered forms. The antimicrobial action of organic acids, such as propionic and formic acid, is well known (Partanen and Mroz (1999), Canibe and Jensen (2003), Mroz (2005), Koyuncu et al. (2013)). Recently, the EU has categorised formic acid as a feed decontaminating agent against Salmonella and other pathogens (EU 2017/940). OA have long since been suggested as alternatives for antibiotics

and have shown piglet growth benefits (Roth and Kirchgessner, 1989). The mode of action in this paper was suggested as helping to reduce the stomach pH of piglets and reducing the pathogenic load in the gut associated with weaning. However, it is not easy to alter the pH of the feed directly: Figure 1 shows the buffering capacity of raw materials and a compound feed (adapted from Bolduan 1988). It is more likely that OA help reduce the buffering capacity of the feed so that native hydrochloric acid in the stomach is more effective. This can help to improve the action of endogenous and in-feed enzymes, improving protein and fat digestibility but also playing a role in enhancing phytase efficacy (Jongbloed et al. (2000), Omogbenigun et al. (2003)).

Figure 1: Buffering capacity of various feed materials

Mode of Action of Organic Acids Theacidpenetratesthecellwall

Gramnegativebacteria e.g. Salmonellaspp.

Organic acid (AH)

Figure 2: Mode of antibacterial action of organic acids Stage 1

Lacticacidproducingbacteriae.g. Lactobacilli

Theacidpenetratesthecellwall Positively charged hydrogen ions (H+)

Negatively charged anions (A-)

AH move into the cell & dissociate acidifying the internal cell environment.

Mode of Action of Organic Acids Removalofprotons

Stage 2 Enterobacteria e.g.Salmonellaspp.

Lacticacidproducingbacteriae.g. Lactobacilli


The cell is acid tolerant, so is able to cope with a greater pH drop

The cell uses energy to power the proton pumps which move H+ out of the cell.

Mode of Action of Organic Acids Celldies

Stage 3

Gramnegativebacteria e.g. Salmonellaspp.

Lacticacidproducingbacteriae.g. Lactobacilli


Less energy used in moving H+ out of the cell.

AsthecellisusingallofitsavailableenergymovingH+ outofthecellnormalcellfunctionisimpaired. InhibitionofDNAreplacementoccursleadingtocell death.

Theenergyexpendedislowmeaningmoreenergyis availablefornormalcellfunctionandviability.

Mode of action OA can also exert a prebiotic function as they drive localised pH reduction in the gut through modulation of the gut microflora and promotion of acidophilic bacteria, such as bacteria from the genus Lactobacillus. This more acidic environment selects against Gram- negative bacteria such as Salmonella and E. coli which prefer a more alkaline environment, as Gram-negative bacteria expend more energy to excrete H+ ions out of the cell. Like Salmonella and E. coli, Coliforms and Listeria are also challenged in this scenario (Suiryanrayna and


Ramana 2015). Figure 2 gives an example schematic of the acid dissociation and effect on Gram-negative bacteria. This results in the modification of the gut bacterial population. Generally, an increase in the population of putrefactive bacteria such as Salmonella spp. and E. coli is seen at the time of weaning. This is because the overall diet digestibility is reduced compared to milk protein and more undigested feed makes its way to the lower gut, resulting in a loss of nutrients to the piglet, as it is utilised by undesirable bacteria. OA can help to stop this by maintaining a healthy gut environment which favours beneficial bacteria.

Modifi cation of the gut microfl ora Lactobacillus spp. are associated with high performing, healthy animals and are the focus of many prebiotics and probiotics (De Angelis et al.,

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