Date Published: October 26, 2007
Publisher: BioMed Central
Author(s): Charlotte H Johansen, Lotte Bjerrum, Karl Pedersen.
The ionophoric coccidiostat salinomycin is widely used in chicken feed. In the near future the use of ionophore coccidiostats may be banned as has been the case for other antimicrobial growth promoters. This study was conducted to examine the effect of salinomycin on Campylobacter jejuni infection and on the composition of the caecal microflora in broiler chickens.
An experimental infection study was carried out in isolators and the intestinal microflora was analyzed using quantitative cultivation, denaturant gradient gel electrophoresis (DGGE), cloning and sequencing.
We found no effect of salinomycin on C. jejuni but salinomycin significantly affected the composition of the microflora. In addition, salinomycin significantly reduced the prevalence of Clostridium perfringens and we observed a significant increase (62%) in the mean body weight of salinomycin treated chickens compared to un-treated controls.
Termination of the use of ionophore coccidiostats will not affect food safety related to campylobacter, but will increase the risk of necrotic enteritis in the broilers.
Salinomycin is an ionophoric coccidiostat, which is widely used as a supplement in poultry feed to control infection with coccidia . In addition, it is known that salinomycin, has an inhibitory effect on Clostridium perfringens. Thus, the use of salinomycin leads to a decrease in the incidence of necrotic enteritis in broiler chickens [2-7]. It has also been reported that salinomycin can reduce the prevalence of salmonella in chickens . However, Scalzo et al.  found no reduction in the frequency or the level of salmonella shedding by the use of salinomycin. In fact, they observed an increase of one log unit on salmonella colony forming units (cfu) between control and salinomycin treated chickens.
In this study we found no effect of salinomycin on a C. jejuni infection in chickens. This is in agreement with Bolder et al  who found that salinomycin was unable to affect both the incidence and the degree of campylobacter shedding. However, by using the fingerprinting technique DGGE, we found that salinomycin had an effect on the intestinal microflora of the caecum after 5 days of treatment (Day 13) in control chickens and after 15 days of treatment (Day 23) in C. jejuni infected chickens. Knarreborg et al.  found a similar effect of antimicrobial supplementation on the composition of the microflora in the ileum of broilers. By using group specific primers these authors showed that lactobacilli and C. perfringens were most strongly affected by the antimicrobial treatment.
In conclusion, salinomycin did not affect the course of a Campylobacter infection in broiler chickens. This observation is important and indicates that cessation of the use of ionophore coccidiostats will not affect food safety related to Campylobacter. However, salinomycin caused a pronounced increase in the body-weight of the chickens. Also, an effect on C. perfringens and on the normal intestinal microflora was observed, and the numbers of C. perfringens were significantly reduced by salinomycin. C. perfringens is normally present in the intestinal microflora of 75% to 95% of broiler chickens [21,22,22]. Thus, a stop in the use of ionophore coccidiostats will most likely lead to an increase in the cases of necrotic enteritis, to a lower performance and to an increased mortality in broiler flocks unless other measures are installed to control C. perfringens.
The author(s) declare that they have no competing interests.
CJH, LOB and KPE were involved in the study design and performance of the infection experiment. CJH did the DGGE work. CJH were responsible for the data analysis and manuscript preparation. KPE and LOB participated in study design and manuscript revision. All authors have read and approved the final manuscript.