The use of antibiotics to improve growth or feed utilization in broilers is undergoing considerable scrutiny. In the European Union, the use of all such antibiotics has been banned by regulatory measures, and in the United States, many major poultry buyers are placing demands on broiler producers to supply chicken grown without antibiotics. A number of alternatives to replace some or all of the functions of antibiotics have been sought, but none have been universally adopted by the industry.

From the literature

One product that has been demonstrated to be effective in promoting growth and feed utilization in broilers is fumaric acid. In 1979, researchers in Germany added this organic acid to broiler diets in three trials. The addition of fumaric acid increased bodyweight significantly in one trial and improved feed conversion in all three trials by between 1.3 and 7.3 percent. Another German scientist noted improvements in both bodyweight and feed conversion from the addition of 2 percent fumaric acid to broiler diets. Later, he and a co-worker reported that the addition of 0.9 percent fumaric acid resulted in improved feed conversion by broilers. In 2001, another group found that supplementing broiler diets with 1 percent fumaric acid resulted in better growth rate and feed efficiency. A mixture of fumaric, lactic, citric, and ascorbic acids in broiler starter diets improved performance of birds in the absence of antibiotics. As might be expected, however, not all studies have shown such positive improvements.


Arkansas experiments

Several trials conducted in our laboratory have shown positive improvements in broiler performance from the addition of fumaric acid. In the first study, published in 1988, fumaric acid was added at levels up to 1.5 percent and fed to 21 days of age to chicks in wire-floored battery pens. The results are shown in Table 1. Feeding levels of 0.5 or 1.0 percent gave a significant improvement in bodyweight. Although feed efficiency was numerically improved, the differences were not statistically significant.


In our second study published in 1991, fumaric acid was added to diets at levels up to 0.5 percent and fed to chicks from hatch to 49 days of age in litter floor pens under simulated commercial conditions. Bodyweight was significantly improved by the addition of 0.125 or 0.25 percent fumaric acid, while feed conversion was improved by all levels of fumaric acid, as shown in Table 2. Mortality was reduced in a linear manner by the addition of fumaric acid. No adverse effects on dressing percentage or abdominal fat were observed by addition of fumaric acid.


Latest results

In a recent test conducted in our laboratory, broiler chicks were fed diets supplemented with 0.125, 0.25 or 0.5 percent fumaric acid or with a popular antibiotic program consisting of 50g/ton bacitracin from 0 to 35 days followed by 15g/ton of virginiamycin from 35 to 42 days of age. The birds were grown in litter floor pens under simulated commercial conditions. Table 3 shows that the addition of the antibiotics or the fumaric acid resulted in numerical improvements in bodyweight but the differences were not statistically significant. Addition of the antibiotics also resulted in numerical improvement in feed conversion, while the addition of 0.5 percent fumaric acid significantly improved feed conversion in comparison to the negative control.


The results of studies in our laboratory and those from other researchers have consistently shown improvements in feed conversion from the addition of fumaric acid to the diet. While the effects on bodyweights have not been consistent, several studies have also shown improvements in this measurement. The mechanism by which fumaric acid improves performance in broiler chickens has yet to be determined. Various authors have suggested alterations in gut pH, activation of protease enzymes and/or modification of intestinal micro flora as possible modes of action. Results-to-date suggest that fumaric acid may be valuable as a feed additive in broiler diets to aid in overcoming reduced performance associated with the reduction or elimination of growth promoting antibiotics in broiler diets. At the present time, fumaric acid is considered as ‘Generally Recognized as Safe' (GRAS) at levels up to 0.5 percent as a pH adjuster, preservative or flavoring agent in animal feeds.

This article first appeared in Poultry International.