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Using organic acids to promote growth and reduce cellulitis rejects

Nathan Hiom BVSc MRCVS

Rejects across the broiler industry have been increasing year-on-year and are often down to cellulitis. The reasons for the cellulitis can include disease challenge such as gumboro, water sanitation and high bacterial loading.

The benefits of promoting a healthy gut bacterial population is well documented. However, trials into the use of organic acids specifically to reduce cellulitis rejects, as well as to promote growth have been limited.

This trial looked specifically at the use of organic acids to reduce the number of rejected birds in the abattoir as well as to promote growth rates.

The digestion process – a reminder

When looking at a bird’s digestion, this obviously starts at the beak where salivary glands begin the digestion process. Feed then descends into the crop via the esophagus, with the crop acting as an expandable storage component. Feed then passes into the proventriculus where digestive enzymes are released and then into the gizzard which is effectively a muscular stomach for mechanical breakdown.

The small intestine consists of the duodenum, jejunum and ileum where nutrients are absorbed. The lower intestine absorbs water and uses bacteria to help digestion, with the caeca helping with fermentation of undigested feed.

Any remaining products pass through the cloaca and are excreted.

The microbiome of the gut

The digestion and absorption process involves a whole network of different mechanisms and components that require specific conditions in the gut to work effectively. In addition, the bird uses microorganisms to help with digestion.

For scale, it’s predicted that over 50% of cells in the chicken at any one time are bacteria. Multiply that by 100 and that will be the number of viruses present.

This population of bacteria, viruses and other microorganisms is referred to as the microbiome of the gut.

The microorganisms that make up the microbiome of the gut are initially transferred from the hen and subsequently the environment in the first few days of life. In the hatchery the birds will receive probiotics – good live bacteria – to help with colonisation in the gut.

The difference to a good or bad crop

The beneficial gut microbiome, consisting of a complex mixture of good bacteria including lactobacilli and peptidococcus species, will promote digestion and growth rates and develop the immune system.

An increase in bad bacteria like salmonellas, E coli and some clostridium species, will decrease growth rates, cause disease, and impede bird welfare.

In summary, a good microbiome can be the difference between a very poor and a very good crop. When the microbiome on site shift in the poor direction, either due to a potential pathogenic cause or environmental issue, it can be difficult to reverse, often resulting in a number of consecutive poor crops.

The important role of acidity in the gut

Acidity plays an important role in the gut. A pH of 7 is neutral, 1 very acidic and 14 very alkaline however that scale isn’t proportional. For example, a pH of 4 will be 10 times as acidic as a pH of 5.

The top part of the gut in the proventriculus and the gizzard is naturally acidic. The lower part is naturally neutral, if not slightly alkaline. Most bacteria can be found in the lower part of the gut in the alkaline conditions. And this is where organic acids have an impact.

A normal acid will not reach the lower part of the gut as it will lose its acidic properties in the face of a weak alkaline environment. By using a buffered acid, the acidic properties remain unaffected and will reach the bacteria in the lower part of the gut.

The bad bacteria will actively try to remove this acidity, until it runs out of energy. When this happens, the bad bacteria will die or at least have reduced viability. Conversely, the good bacteria prefer the acidic environment and will thrive.

Cellulitis and gut health

For cellulitis to develop, birds need a scratch or some type of wound damage that is infiltrated by bacteria – usually E coli.  

Using acids reduces the E coli levels in the gut which in turn reduces the E coli levels that are shed through the droppings. The reduced E coli burden in the environment consequently reduces the risk of contamination into the wounds.

Another benefit of good gut health is that birds tend to become less flighty and therefore less prone to scratches generally.

Background to the trial

The trial site, that consisted of eight houses with 40,000 birds in each that were all identical and managed in the same way, had consistently underperformed and struggled with poor gut health. Growth weights were average however there were a high number of cellulitis rejects regularly.

After a review of the brooding and the environment that included extensive sampling, including water hygiene, the only issue identified was consistently high cocci and enteritis across the site.

The trial

At the start of the crop, four houses were placed on the organic acid program and four houses were not.

The organic acid program consisted of ABC Start for the first 13 days, followed by ABC pH from day 18 to 38. ABC Start contains lactic acids, copper and organic acids to encourage the development of the microflora, and ABC pH is a buffered solution with propionic acid, lactic acid and acetic acids, that together with other components create an environment that benefits the good bacteria. Water sanitation was also important intermittently to prevent biofilm build up.  

The entire crop progressed well with no particular issues in any of the houses. Faeces were firm and of the appropriate coloration and consistency throughout.

The results

The following are the first crop’s results into the factory.

In addition, postmortems were carried out at 22 days, with no awareness of which birds came from an acid, or non-acid house.  

The cocci scores from the acid houses were half that of the non-acid houses and the gut health was significantly better, with minimal signs of enteritis. To add to that, no medication was using in the organic acid houses.

For the first crop, the cost per bird of the acids was 1.3p. The benefit per bird equated to 8.8p.

Future trials

The organic acid program has since been trialled on additional sites – the results of which will be shared shortly.

A focus area for future trial crops will be the effect using organic acids has on cocci, as the decreased total mean lesion score was unexpected in the phase 1 trial. As a secondary effect, it’s possible that the improvement in gut health has reduced the cycling of cocci.

If you’d like to know more about the using of organic acid, please contact your local vet, or call the team: 01392 872932.

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