Improve intestinal flora with benzoic acid

25-09-2013 | |
Improve intestinal flora with benzoic acid

Broiler performance can be enhanced by improving their intestinal flora with benzoic acid. However, due to ?differences in metabolism of poultry compared to pigs, just feeding them benzoic acid has little results. Getting it to the lower intestines is key.

The gastrointestinal tract with its complex micro flora plays a key role in growth performance and health in modern broiler production. A variety of factors such as diet, stress, disease and management can have a negative effect on the balance of the intestinal micro flora resulting in poor growth and feed efficiency. In the past, antibiotics at sub-therapeutic levels have been used to control the gut flora indirectly obtaining an improvement in broiler growth. However this option is now no longer available to the broiler producer and a number of feed additives and nutritional strategies have been developed, with greater or lesser success, to stabilise or manipulate the intestinal micro flora.

Organic acids, mainly formic acid based blends, are widely accepted/used in poultry production systems to prevent the growth of potential pathogenic bacteria in the feed and to maintain a balanced flora in the intestines. With good intestinal flora the birds need less energy to fight harmful bacteria, leaving more energy for growth. Similarly, benzoic acid is being used in piglet diets at levels of up to 1% resulting in an improved growth performance. In poultry, however, the pathway for benzoic acid metabolism is different from that in pigs. Benzoic acid in a free form in chicken starts to disintegrate in the crop and is rendered almost useless before it reaches the lower intestines. This may explain why trials in which the acid has been incorporated into broiler feed at between 0.25 and 0.75%, have resulted in less optimal performance.


Research has shown that benzoic acid can survive the upper stages of the broilers intestinal tract by encapsulating it in vegetable fat. However, covering the large flakes of benzoic acid by fat, didn’t have the desired targeted release. Milling the potential explosive benzoic acid down was a big problem, until recently. The opening of an state of the art processing plant by Novus, paved the way for a new product, which incorporated all the wishes concerning benzoic acid. Small particle size, encapsulation by vegetable fat and thus targeted release in small amounts throughout the lower intestines to allow the active anti-bacterial ingredients to be delivered in the lower parts of the gut. The product, called Avimatrix, is based on a vegetable fat embedding matrix, calcium formate and a mixture of flavouring compounds with benzoic acid being the major ingredient. Compared to a standard/ normal encapsulation technology, this offers the advantage of a slow and continuous release of the active ingredients along the entire intestinal tract of the bird.


This new concept was tested in a number of scientific studies in coordination with various research institutes around the EU. Rather than using single bacterial species in an in vitro model, Novus has developed an in-feed intestinal model to simulate conditions in the intestinal tract. This provides a more rigorous evaluation of the impact of different blends of active substances on the complex micro flora of the gut.

One of the first performance trials was done in 2009 (Roslin Nutrition, UK) to study the effect of increasing dosages of Avimatrix in pelleted diets formulated to meet the nutritional needs of growing broilers. In addition the performance was compared to the effect of a negative control, a positive control using free benzoic acid and three dosages of Avimatrix, 250, 500 and 1.000 grams per ton.

Birds receiving the diets containing Avimatrix had a significantly higher body weight at 42 days (Figure 1) when compared to the negative control diet as well as the positive control diet containing the free benzoic acid (p<0.05). Even the low inclusion levels of 250g/t Avimatrix improved the final weight by 175g when compared to the control or 96g vs. the free benzoic acid group. The response to Avimatrix appeared to be curvilinear (Figure 2) with the optimum inclusion rate at 500g/t, equivalent to 250g/t of benzoic acid. Calculation of FCR for the entire growth period showed all Avimatrix treatments to be significantly better than the control group (p<0.05).

EFSA guidelines

Similar results were obtained over a three year research programme in which Avimatrix has been tested at four independent European research facilities. A method, known as “Meta Analysis” which evaluates pooled data from a number of studies, was used to evaluate the overall effect. This method is required when submitting a dossier to the EFSA expert committees for new product registration. Novus is in the process of getting a registration for their product for zoological application as growth enhancer. Most other products are only registered as aromatic compound.

Encouraged by the scientifically 
proven support on bird performance, the product has been tested recently under commercial conditions in an European broiler integration. About 160,000 one day old Cobb 500 pullets were divided into two groups. Both groups originated from the same hatchery. The birds were fed pelleted diets (4 phase feeding) supplemented with 500g/t Avimatrix or without (control group). Correcting the feed conversion ratio to the same weight the birds receiving Avimatrix had a lower FCR of 0.085 points (Figure 3) which is equivalent to an improvement of 4.5%. As a result the feeding cost per kg of body weight was reduced with 4.4%. These savings resulted in a 3.5% higher financial outcome with a return on investment of 1:6.7.

Important ‘side-effect’

A recent study at the University of Bologna (2012) analysed the effect of using Avimatrix in diets for broilers on the litter quality and foot pad health. The usage of the product resulted in reduced litter moisture content with an additional clear difference in the incidence of foot pad lesions. Birds receiving the control diet only had 37.5% of healthy foot pads whereas 45% of the birds fed with Avimatrix had no lesions. At the same time the number of mild lesions (Score 1) was reduced with almost 10% by using the product.

A higher incidence of FPD often occurs when the moisture content in litter increases and both conditions can be linked to a breakdown in the balance of the gut micro flora. FPD is also used as a key indicator for animal welfare. Therefore any reduction in the incidence of footpad damage will have an impact on this production parameter and also on carcass quality.

Co authors:
Dr Sven Keller & 
Dr David Parker

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Fabian Brockotter Editor in chief Poultry World