Acidification and fermentation of pig diets

Changing the chemistry of feed and water offers a range of potential benefits which can increase the performance and gut health of pigs. Find out how this can reduce your reliance on zinc oxide, decrease the need for antimicrobials and improve feed conversion ratios (FCR).

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Acidification of feed and water 

Bacteria, especially those that cause disease, are sensitive to changes in the overall acidity of the environment in which they live. The scale of acidity is measured in pH and is referred to as the pH scale.  

A low pH value has higher acidity, a pH value of 7 is considered neutral, and a higher pH value is considered alkaline.

Cleaning a water system and choosing organic acids

Adding acids to drinking water as an element of biosecurity has been well documented and is usually achieved using automated dosing machines. These machines can be integrated into existing waterlines and are often referred to as in-line dosers.

Like all of the solutions described as an approach to reducing reliance on zinc oxide, acidification is only one element of the solution, and it is essential that high standards of overall management, biosecurity and health are maintained.

Even with acidification of the waterlines, biofilms (layers of bacteria on the inside of pipes) can develop. These can restrict water flow and lead to health issues in the pigs. Routine sampling and cleaning of water systems is essential to avoid having to add too much acid (increasing overall costs) or adding too little (false economies as there is little impact).

We have produced a range of supporting materials on the appropriate cleaning and maintenance of water systems in pig buildings: 

Fermentation of feed 

Those using a liquid feed system have the opportunity to explore the fermentation of feed. There are two key reasons to ferment feed: 

  1. To destroy harmful disease-causing bacteria and promote friendly bacteria. 
  1. To partially break down complex feed ingredients (often cheaper by-products/coproducts) to allow efficient digestion and absorption of key nutrients. 

The principle of fermentation is like the fermentation of bread and alcohol, and there are some key principles that must be adhered to. 

Cleanliness: sterile working conditions in feed preparation, routine cleaning and flushing of feed lines, and deep cleans of the feed hoppers are essential to avoid introducing harmful bacteria into the process. 

Temperature: the fermentation process has an optimum temperature, typically around 37C. This must be maintained throughout the fermentation process. 

Fermentation of pig feed

Fermentation of feed – case study 

Zinc oxide has historically been included in pig diets to prevent post-weaning diarrhoea. However, high levels can have adverse effects on pig performance and the environment.  

Therefore, the EU has banned the use of medical zinc oxide from 2022. This, combined with the increased demand for a reduction in antibiotic use, drastically increases the need for the pig industry to find alternatives to help prevent intestinal disorders. 

The Van Asten Group in the Netherlands set out to improve the gut health of sows, piglets and fattening pigs and reduce antibiotic and zinc oxide use. Across a period of three years, they introduced fermented liquid feeding and, initially, saw a 50% reduction in antibiotic use. 

Equipment and feed lines are cleaned with 70°C water for sterilisation. Feed raw material is also mixed in 70°C water to kill all bacteria present. After mixing, cooler water and liquid active bacteria are added to reduce the temperature and secure fast growth. Temperature and cleanliness are important to obtain good lactic acid values and low acetic acid. The lactic acid metabolises anti-nutritional factors (ANF) and difficult digestible starch; this acts as a probiotic and lowers the pH to reduce the risk of bacteria.  

Fermented liquid feed helps to stabilise the environment in the pig’s intestines and improves growth rates. For maximum effect, it is fed together with a wheat-barley mixture and plant-based proteins. 

Sows and pre-weaned piglets should also be fed fermented liquid feed to achieve optimal results in weaned piglets. This system can be easily adapted and used by a person who has experience with liquid feeding systems. Enough capacity is needed to produce the fermented product – once produced, the feed can be stored in tanks for 24 hours.  

The use of fermented liquid feed appears to be a cost-effective alternative to the use of antibiotic growth promoters, as well as making use of local protein. 


  • The energy for heating and managing the feed will increase by 3% for sows and 5% for finishing pigs 
  • Investment costs are approximately €16 per pig space 


  • Sow mortality was reduced by 33%, pre-weaning mortality by 15%, rearing mortality by 24% and finishing pig mortality by 17% 
  • A reduction in production costs of 3.3% 
  • A 5% reduction in the average cost of feed 
  • A 3050% decrease in veterinary and medicine costs 
  • Production costs reduced by up to €2.70 per pig space 
  • Up to 80% antibiotic reduction 
  • A 25% reduction in phosphorus and nitrogen in the diet 
  • Sows wean half a piglet more per litter 
  • Litter weight at 24 days is 0.5 kg heavier 
  • Feed is more palatable and consistent in quality 

Read the full technical reports and find supporting materials on the EUPiG website