May 2016: Acid test for gut health

Organic acids have won their place in the armoury as an alternative in pig diets to antibiotic growth promoters (AGPs). In fact, they’re at the forefront of the range of alternatives for AGPs, and they’ll help to combat gut health issues and improve the overall efficiency of feed use on farm. They’re equally effective in weaned piglet diets, and diets for the rest of the herd.

In fact, I can go as far as saying that an organic acid blend is a must in piglet starter feeds to promote a healthy and thriving digestive system.

At weaning, piglets are exposed to heavy stress, and the better their digestive system is developed, the better they’ll cope with changes like diet, that so often can result in a fall in intakes.

A post-weaning dip is linked to little, if any, weight gain – it’s literally a dip in performance. There’s insufficient hydrochloric acid and pancreatic enzyme production in the gut, and this affects its digestive and absorptive capacity.

Lowering the dietary pH by using organic acids helps to overcome these problems. It lowers the gut pH, allowing an increase in activity of the enzyme pepsin that improves protein digestion. This benefits both feed efficiency and the environment, with, for example, lower ammonia emissions.

A diet with a lower pH – one that includes organic acids – will encourage dietary changes in the villus height and depth in the small intestines in young piglets, and this increases the digestibility of nutrients.

Despite many starter feeds – and other pig feeds – now including organic acids, the combination or make-up of the blend is important and linked to its performance. Different dietary proteins need different pHs for maximum digestibility.

Casein, the protein in milk, needs a gut pH of 4.0 to coagulate, precipitate and reach a maximum digestibility. Pepsin activity on vegetable and fish proteins, which appear in most starter diets, is most efficient at a pH of 2.0 to 3.5, and this can only be achieved by using organic acids. This calls for a carefully formulated organic acid blend that can provide a broad range of activity in the gut.

Here are a few more examples that demonstrate the intricacies of organic acids. Citric acid is highly soluble and reduces gut pH immediately after a meal. Fumaric acid is less soluble and will maintain the pH decrease for longer, even when the citric acid has dissolved. Other organic acids, meanwhile, such as formic acid, have a direct microbial effect by reducing the buffering capacity of the diet and killing pathogenic bacteria such as E coli.
Acids may also stimulate the production of positive bacteria such as lactobacillus. It’s also worth noting that it’s very important to include an acid that protects feeds from spoilage by yeasts and moulds in acid combinations used in liquid-feeding systems.

A large bank of research has been put together on the use of organic acids in pig diets, although there’s still a lot more to learn. But, for now, the key message is to be discerning and make sure there’s some good science behind the organic acids in the diet so maximum gain is up for grabs.

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About The Author

Barry Hoare is Cargill's pig nutritionist for the UK and Ireland. Based in southern Ireland, he graduated from University College Dublin with a masters degree in pig nutrition in 2001