December 2015: Acids – the Swiss army knife of pig feed!

Acids are a vital component in pig diets, but do we really appreciate their crucial role, where they come from, and what they do? Possibly not, but I think it’s worthy of some explanation.

It’s fair to say that acids are responsible for much more than you would imagine. There are three chemistry definitions for acids that have developed over the years, but all are fundamentally based around the action of positively charged particles at a molecular level.

The acids we are most familiar with (as introduced to us in our school lessons) are hydrochloric, sulphuric and nitric. They are otherwise chemically described as HCl, H2SO4 and HNO3, and all have the element hydrogen (H) in common. It’s this that provides the “acid” effect in a solution, as it’s positively charged and desperately wants to be neutralised, subjecting any material it comes into contact with to attack and, in the process, it compromises its integrity.

For pigs, as well as ourselves, the most important acid is hydrochloric acid as a critical component of digestion. When food is encountered – by sight, taste and smell, the body responds automatically by producing a hormone called gastrin that is circulated in the blood. Gastrin, in association with additional chemicals secreted by the vagus nerve (that also controls such critical body functions as heart rate, passage of food through the gut, sweating and speech) signal the parietal cells in the stomach to produce hydrochloric acid. This then reacts with another secreted chemical known as pepsinogen from different stomach wall cells (chief cells) to produce the enzyme pepsin, which is critical in digesting proteins and the subsequent conversion to lean tissue, enzymes and other proteinaceous substances.

Weaned piglets have a low capacity to produce hydrochloric acid, which has an impact on their capability for protein digestion. In order to help overcome this, we look to offer additional acids in the feed or through the water to help boost the processes. However, we can’t use hydrochloric acid this way for many practical and health and safety reasons, so we use a range of organic acids to provide the necessary hydrogen atoms.

Unlike the three acids mentioned earlier, that are described as inorganic acids, the thing that all organic acids have in common is the presence of a carbon atom – which is the very definition of organic chemistry. A good example is formic acid, which is produced naturally by some ants and has the formula HCOOH.

This, among other organic acids, will commonly be found in piglet starter feed, improving protein digestion, but also has key roles in feed preservation and the control of micro-organisms. Each organic acid has different properties in its ability to control bacteria, moulds and yeasts.

With this multifactorial role in diets, a great deal of work has been put into creating the most effective blend of acids, their mode of action and exact region in the body for optimum efficacy. This work continues, and with the obvious pressure on reducing antibiotic usage, they’ll provide a vital role in supporting pig performance, either in the feed or through water lines.

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About The Author

Dr Phil Baynes has spent his career in pig welfare and nutrition. Based in Cheshire, he runs Baynes Nutrition and is a consultant nutritionist to Provimi.