Effect of resinous extract from Commiphora swynnertonii (Burrt) on experimental coccidial infection in chickens

A crude resinous extract from Commiphora swynnertonii was tested against an experimental coccidial infection in local chickens. A total of 80 growing chickens were randomly assigned into five groups, which received different treatments. Chickens in G1 were not infected with coccidian oocysts and therefore served as a negative control. All chickens in G2, G3, G4 and G5 were infected through oral administration of coccidian oocysts suspension at a dosed rate of 1.5?×?10⁴ Eimeria spp. oocysts per bird. Starting from day 3 post-infection (p.i), chickens in different groups were treated for 7 consecutive days as follows: G1 and G2 (positive control) received 5 ml of normal saline as placebo, G3 and G4 were given the extract at 400 and 800 mg/kg bodyweight whereas G5 received anticoccidial drug. Clinical signs, bodyweights, oocysts counts and mortality rates were observed regularly. Results showed that oral administration of the resinous extract to chickens with coccidiosis significantly reduced mortality rate from 94 to 25 % and oocysts counts from 1.03?×?10⁵ to 6.55?×?10³ oocysts/g faeces (p?<?0.05). Also a body condition score chart indicated less severe clinical signs of the disease in the groups which received the extract. Mean daily body weights were slightly reduced by the administration of the extract but this effect disappeared by day 7 p.i. These findings clearly indicate that resinous extract from C. swynnertonii has significant anticoccidial effect against experimental Eimeria spp. infection in chickens. A larger field trial to validate the use of the extract in chickens naturally infected with Eimeria spp. is required.     

Inclusion of Bacillus amyloliquefaciens strain TOA5001 in the diet of broilers suppresses the symptoms of coccidiosis by modulating intestinal microbiota

Coccidiosis is an intestinal parasitic infection and one of the most prevalent and economically damaging diseases of chickens. Furthermore, coccidia‐induced mucogenesis promotes secondary colonization by Clostridium perfringens, a major pathogen of chickens that causes necrotic enteritis. Our previous work found that supernatant of a culture of Bacillus amyloliquefaciens strain TOA5001 (BA) inhibited the growth of C. perfringens on Gifu anaerobic broth medium. Accordingly, we evaluated the effectiveness of dietary BA administration in inhibiting C. perfringens colonization of the intestine in broilers that were experimentally infected with coccidia. Ten healthy broilers from a BA‐supplemented (2 × 10⁵ colony‐forming units/g of feed) broiler group and 10 from a non‐treated group were challenged with Eimeria tenella and E. maxima (5000 oocysts of each species/chick) at 28 days old. At 36 days old, five chicks from each group were slaughtered, whereas the remaining five in each group were killed at 49 days old. Dietary BA administration into Eimeria‐challenged birds reduced coccidial symptoms such as intestinal lesions. It also modified the cecal microbiota through suppressing C. perfringens and E. coli colonization, and inducing domination of Faecalibacterium prausnitzii, the Lactobacillus group and unknown Lachnospiraceae genera by bacterial DNA‐based metagenome analyses. B. amyloliquefaciens TOA5001 supplementation suppressed the symptoms of coccidiosis by modulating cecal microbiota in Eimeria‐challenged broilers.     

Effects of Artemisia annua and Foeniculum vulgare on chickens highly infected with Eimeria tenella (Phylum Apicomplexa)

Background

Intensive poultry production systems depend on chemoprophylaxis with anticoccidial drugs to combat infection. A floor-pen study was conducted to evaluate the anticoccidial effect of Artemisia annua and Foeniculum vulgare on Eimeria tenella infection. Five experimental groups were established: negative control (untreated, unchallenged); positive control (untreated, challenged); a group medicated with 125 ppm lasalocid and challenged; a group medicated with A. annua leaf powder at 1.5% in feed and challenged; and a group treated with the mixed oils of A. annua and Foeniculum vulgare in equal parts, 7.5% in water and challenged. The effects of A. annua and oil extract of A. annua + F. vulgare on E. tenella infection were assessed by clinical signs, mortality, fecal oocyst output, faeces, lesion score, weight gain, and feed conversion.

Results

Clinical signs were noticed only in three chickens from the lasalocid group, six from the A. annua group, and nine from the A. annua + F. vulgare group, but were present in 19 infected chickens from the positive control group. Bloody diarrhea was registered in only two chickens from A. annua group, but in 17 chickens from the positive control group. Mortality also occurred in the positive control group (7/20). Chickens treated with A. annua had a significant reduction in faecal oocysts (95.6%; P = 0.027) and in lesion score (56.3%; P = 0.005) when compared to the positive control. At the end of experiment, chickens treated with A. annua leaf powder had the highest body weight gain (68.2 g/day), after the negative control group, and the best feed conversion (1.85) among all experimental groups.

Conclusions

Our results suggest that A. annua leaf powder (Aa-p), at 1.5% of the daily diet post-infection, can be a valuable alternative for synthetic coccidiostats, such as lasalocid.     

Comparative analysis of evaluation parameters in E. acervulina,E. maxima and E. tenella-infected broilers

Three parameters, body weight gain (BWG), intestinal lesion score (LS) and fecal oocyst shedding, were compared in broilers infected with major parasitic species; Eimeria acervulina, E. maxima, and E. tenella. First, two- and three-week-old chickens with Eimeria infection showed LS of approximately 3, but two-week-old chickens were more correlated with BWG. Second, significant differences in BWG were observed between male and female broilers challenged with Eimeria. Finally, E. maxima-infected broilers among three Eimeria species showed a higher relationship between BWG and LS, suggesting three considerations such as genders, age and Eimeria species for Eimeria experiments.     

Direct effects of Moringa oleifera Lam (Moringaceae) acetone leaf extract on broiler chickens naturally infected with Eimeria species

Avian coccidiosis is one of the most important diseases of poultry and it is responsible for a large number of all broiler mortalities worldwide. The control of this disease relies mainly on the use of anticoccidial drugs. However, herbal preparations could be an alternative for the treatment against coccidiosis in chickens. The direct effects of Moringa oleifera acetone extracts on broiler chickens naturally infected with mixed Eimeria species was investigated to determine the relative efficacy of the extracts against coccidiosis in birds. The investigations were carried out in seven groups (ten chickens per group). The birds were given various doses (1.0, 2.0, 3.0, 4.0 and 5.0 g/kg body weight) of acetone extract of leaves of M. toltrazuril® (positive control) and untreated (negative control). The extract was evaluated for anticoccidial activity by means of inhibition of oocyst output in faeces, faecal score, weight gain and mortality. Haematological indices were evaluated by standard methods. The group treated with 1.0 g/ kg body weight Moringa oleifera extract produced the least inhibitory effect on oocyst shed in the faeces (96.4 %), while the groups treated with 2.0 g/kg, 3.0 g/kg, 4.0 g/kg and 5.0 g/kg body weight of the extract produced 97.4, 98.7, 99.1 and 99.8 %, respectively. Body weight gains of infected chickens treated with the extract significantly improved (p?<?0.05), and faecal scores were milder. Packed cell volume, haemoglobin concentration and red blood count of the treated birds were significantly (p?<?0.05) higher than those of the infected untreated group. Moringa oleifera leaves could find application in the treatment of avian coccidiosis in veterinary practice.     

Effect of Bacillus-based direct-fed microbials on Eimeria maxima infection in broiler chickens

The effect of dietary Bacillus-based direct-fed microbials (DFMs; eight single strains designated as Bs2084, LSSAO1, 3AP4, Bs18, 15AP4, 22CP1, Bs27, and Bs278, and one multiple-strain DFM product [AVICORR™]) on growth performance, intestinal lesions, and innate and acquired immunities were evaluated in broiler chickens following Eimeria maxima (EM) infection. EM-induced reduction of body weight gain and intestinal lesions were significantly decreased by addition of 15AP4 or Bs27 into broiler diets compared with EM-infected control birds. Serum nitric oxide levels were increased in infected chickens fed with Bs27, but lowered in those given Bs2084, LSSAO1, 3AP4 or 15AP4 compared with the infected controls. Recombinant coccidial antigen (3-1E)-stimulated spleen cell proliferation was increased in chickens given Bs27, 15AP4, LSSAO1, 3AP4, or Bs18, compared with the infected controls. Finally, all experimental diets increased concanavalin A-induced splenocyte mitogenesis in infected broilers compared with the nonsupplemented and infected controls. In summary, dietary Bacillus subtilis-based DFMs reduced the clinical signs of experimental avian coccidiosis and increased various parameters of immunity in broiler chickens in a strain-dependent manner.     

High prevalence of <Emphasis Type="Italic">Eimeria</Emphasis> infection in dairy goats in Shaanxi province,northwestern China

A survey of dairy goats for infection with Eimeria species of coccidia was conducted in the Shaanxi province, northwestern China between December and November 2010, including Saanen and Guanzhong breeds. A total of 584 fecal samples (250 and 334 from Saanen and Guanzhong dairy goats, respectively) in six farms were collected. Eimeria oocysts were seen in 568 (97.3%) fecal samples, with six species, namely Eimeria jolchijevi, Eimeria arloingi, Eimeria alijevi, Eimeria caprina, Eimeria hirci, and Eimeria christenseni. The most prevalent were E. arloingi in Saanen and Guanzhong dairy goats, with an overall prevalence of 83.3% and 84.4%, and the lowest prevalence were E. christenseni (26.9%) and E. hirci (20.7%) for Saanen and Guanzhong Dairy goats, respectively. Two or more Eimeria species were commonly presented in all the age groups; 80.0% and 81.4% of positive Saanen and Guanzhong dairy goats carried more than two species, and 1.6% and 6.5% of two breeds had six species. The results of the present survey suggested that Eimeria infection is wide and severe in the Saanen and Guanzhong dairy goats, which suggested that integrated strategies should be implemented to prevent and control coccidial infection in dairy goats in this province.     

Differences between the anticoccidial potencies of monensin in maize-based or wheat-based chicken diets

Experiments were carried out to investigate why the anticoccidial ionophore monensin is more potent against the coccidiumEimeria tenella in chickens fed on a maize-based diet (as in the USA) than in chickens fed on a wheat-based diet (as in the UK). The explanation seems to be that the pathogenicity ofE. tenella is lower in maize-fed chickens than in wheat-fed chickens, whether monensin is present in the diet or not. Possible reasons for this are suggested. The better survival of maize-fed birds may be partly due to protective effects of the higher concentrations of vitamins A and E derived from their diet. Furthermore, the higher concentrations of niacin and riboflavin in wheat than in maize may enhance coccidial pathogenicity. These opposing factors might combine to cause equivalent infection levels to produce more severe coccidiosis in chickens fed on a wheat-based diet than on a maize-based diet.     

Effects of dietary supplementation with a herbal extract on the performance of broilers infected with a mixture of Eimeria species

1. A herbal extract containing a blend of three essential oils, derived from oregano, laurel leaf and lavender, was investigated as a feed additive alternative to the conventional anticoccidial sodium monensin.

2. Broilers were infected with a mixture of Eimeria species or left uninfected.

Both infected and uninfected broilers were provided with diets containing either herbal extract (HEX), monensin (MON) or without these supplements (CON). The HEX group had 50?mg herbal extract/kg diet and the MON group 100?mg monensin/kg diet.

3. All of the uninfected broilers exhibited higher body weight gain and better feed conversion when compared with their infected counterparts at d 28 and 42 of age. Both HEX and MON supplements caused significant improvements in performance in the infected broilers, but failed to have any effect on uninfected broilers.

4. Faecal oocyst output measured daily by sampling excreta, and expressed on a per bird basis, was lower in the HEX and MON groups than in the CON group. However, the herbal extract was not as effective as monensin in reducing oocyst excretion. Coccidial infection caused a significant increase in total intestinal length and caecal weight, but the dietary treatments did not influence these measurements.

5. These results indicate that providing a herbal extract in the diet was not as effective as monensin in protecting broilers exposed to a coccidial challenge.     

Prevalence of subclinical coccidiosis in broiler farms in Turkey

The presence of Eimeria spp. oocysts in fecal samples collected from 1,108 broiler houses in six regions, representing about 12% of all broiler farms in Turkey, was studied using the modified McMaster method. The age of the chickens in the 1,108 pens varied from 1 to 50 days. Oocysts were found in 602 (54.3%) of these broiler houses, and the mean OPG (oocysts per gram of feces) in those samples was 36,498.7 (50–952,000). No indication of clinical coccidiosis or other clinically evident infection or wide mortality was encountered in any of the pens studied. Further study showed that the age of the chickens, the occurrence of diarrhea on the houses and the density of broiler breeding in the area correlated with subclinical coccidiosis prevalence.     

Coccidiosis control with toltrazuril in conjunction with anticoccidial medicated or nonmedicated feed

A 42-day broiler floor pen study was conducted comparing the anticoccidial efficacy of toltrazuril (Baycox) as a stand alone treatment and as an additional treatment to in-feed anticoccidial programs. Toltrazuril was administered on days 18 and 19 in the drinking water at 7 mg/kg of body weight. The treatments were 125 ppm nicarbazin (days 0-14) to 66 ppm salinomycin (SAL) (days 15-35) with and without toltrazuril, SAL (days 0-35) with and without toltrazuril, nonmedicated (NM) to SAL with toltrazuril, and NM with and without toltrazuril. The controls were NM noninfected and infected. The treatments were replicated in five blocks of eight pens each in a randomized complete block design. All withdrawal feed was nonmedicated. On day 14, birds, except noninfected, were exposed to coccidial oocysts (Eimeria acervulina, Eimeria maxima, and Eimeria tenella) seeded litter. On days 21, 28, 35, and 42, birds and feed were weighed, four birds per pen were coccidial lesion scored, and litter oocyst counts were performed. The coccidial infection in the NM infected treatment caused a significant (P < 0.05) coccidiosis infection. Coccidiosis was moderately controlled in the anticoccidial treatment birds without toltrazuril. Performance in the NM with toltrazuril was equal to or better (P < 0.05) than the anticoccidial programs without toltrazuril. Toltrazuril was equal to the noninfected birds in performance. Toltrazuril most completely eliminated all coccidial lesions and dramatically reduced oocyst shedding. The performance data, lesion scores, and oocyst counts showed that a 2-day treatment with toltrazuril successfully controlled the coccidiosis with no relapse of infection. Toltrazuril can thus be used for supplemental control with in-feed anticoccidials or as a primary anticoccidial with nonmedicated feed.     

Effects of salinomycin and Bacillus subtilis on growth performance and immune responses in broiler chickens

The present study was undertaken to compare the effect of salinomycin and Bacillus subtilis on growth performance, serum antibody levels against Clostridium spp. and Eimeria spp., and cytokine mRNA expression levels in broiler chickens raised in the used litter. Broiler chickens fed a diet containing salinomycin showed lower (P < 0.05) body weights compared with the control diet-fed counterparts. Serum nitric oxide levels were significantly (P < 0.05) elevated in chickens fed the B. subtilis-enriched diet compared with those on either the salinomycin-fed or control diet-fed chickens. None of the dietary treatments affected (P > 0.05) serum antibody levels against Clostridium perfringens toxins. Both salinomycin and B. subtilis significantly lowered (P < 0.05) the serum levels of Eimeria-specific antibodies compared with the control group. Salinomycin, but not B. subtilis, significantly modulated (P < 0.05) the expression of cytokines encoding interferon-γ (IFN-γ), interleukin10 (IL-10) and tumor necrosis factor superfamily 15 (TNFSF15) compared with the control group. In conclusion, dietary salinomycin and B. subtilis affected serum anticoccidial antibody and intestinal cytokine expression, but failed to improve growth performance in broiler chickens. Further study is warranted to investigate the mode of action of salinomycin on host immune response and growth performance in broiler chickens.     

Epidemiological Studies on Gastrointestinal Parasitic Infections of Lambs in the Coastal Savanna Regions of Ghana

The types of gastrointestinal parasites (Eimeria and helminths) encountered by 70 lambs and the seasonal pattern of both Eimeria and strongylate infections in these lambs in the derived Coastal Savanna were followed for three years. Eimeria oocysts and helminth eggs were detected in the faeces of lambs at the same time, indicating the concurrence of both Eimeria and helminth infections. Eimeria oocysts were first seen in the lambs 20 days after birth (DAB) and the level of oocyst output increased by the fourth week. Eimeria species identified in the lambs were E. parva, E. pallida, E. faurei, E. ahsata, E. bakuensis, E. intricata, E. granulosa, E. ovinoidalis and, occasionally, E. marsica. E. ovinoidalis, the most pathogenic species, dominated the oocyst output during the early part of the life of the lambs. Strongyloides papillosus eggs appeared at 46 DAB, preceding strongylate nematode eggs, which were seen at 57 DAB and those of Moniezia at 69 DAB. The pattern of Eimeria oocyst output paralleled that of the worm egg output, and high oocyst and strongylate worm egg counts corresponded with the period of high rainfall during the study period. Although oocyst and worm egg output fluctuated, high Eimeria oocyst counts were seen again in the lambs when they were 1 and 2 years old. Haemonchus species formed 71% of the infective larvae revealed by larval culture.     

Use of live oocyst vaccine in the control of turkey coccidiosis: Effect on performance and intestinal morphology

An experiment was conducted to determine the effects of different coccidiosis-preventing programs on performance and intestinal morphology of commercial turkeys. Three hundred fifteen1-d-old female commercial cross turkey poults (British United Turkeys, BUT Big 9) were distributed into 3 treatments with 5 replicates of 21 birds each. Three programs were evaluated from 1 to 70 d of age, where program 1 had no anticoccidial drug and no vaccination against coccidiosis; program 2 had an anticoccidial drug (maduramycin 1%, 5 ppm); and program 3 had a vaccination (commercial vaccine, 4 species of Eimeria). All the groups were challenged with a dose of oocysts sporulated (20,000/bird) of 2 species of Eimeria at 21 d of age. In the growing phase (d 0–28), BW, BW gain, and FCR were significantly greater in treated groups compared with control group. In the fattening phase, the performance was not affected by treatments. Treatments and coccidiosis challenge had no significant effects on intestinal villus height. These observations support other reports that confirm live oocyst vaccination can be used effectively as a preventive against avian coccidiosis in commercially reared turkeys.     

Anticoccidial activity of the methanolic extract of Musa paradisiaca root in chickens

The study was designed to evaluate the anticoccidial activity of the methanolic extract of Musa paradisiaca root in chickens. The chickens were divided into six groups of 12 chickens each. Each chicken in five groups was infected with 8,000 infective coccidia (Eimeria tenella) oocysts at day 28 of age while one group served as uninfected control. At day 7 post-infection, two chickens remaining in each group were sacrificed for postmortem examination to confirm coccidiosis. Also at day 7 post-infection, each chicken in four infected groups was given graded doses (250, 500 and 1,000 mg/kg b.w.) of the extract or amprolium (conventional drug). Two groups (an infected and uninfected group) did not receive treatment. Parameters used to assess progress of infection and response to treatment included clinical signs typical of coccidiosis, oocyst count per gramme of faeces (OPG) and packed cell volume (PCV). Treatment of previously infected chickens with M. paradisiaca root extract resulted in a progressive decrease in severity of observed clinical signs, marked reductions in OPG and a gradual increase in PCV. In each case, the changes were dose dependent. There was no significant difference in mean OPG and mean PCV of the extract (at 1,000 mg/kg b.w.) and amprolium-treated groups at termination of the study (at day 50 of age). In the acute toxicity study, the extract was found to be non-toxic to the chickens even at the highest dose of 4,000 mg/kg b.w. The results of this study demonstrated that the extract has anticoccidial activity in a dose-dependent manner and at a dosage of 1,000 mg/kg b.w. had similar efficacy with amprolium in the treatment of chicken coccidiosis.     

The Prevalence and Intensity of Helminth and Coccidial Infections in Dairy Cattle in Central Kenya

A survey of gastrointestinal parasite infections of young (<6 months old), immature (6–12 months old) and adult (>12 months old) dairy cattle on 16 farms in Kiambu District, Kenya was conducted during a dry season (September 1991 to January 1992) and during a wet season (March to July 1992). The survey was based on monthly coproparasitological examination of cohorts and worm counts in tracer calves. The effects of age, sex, farm and season on the prevalence and intensity of helminth and coccidial infections were determined. Faecal egg and oocyst counts revealed that the overall prevalences were: strongyles (including trichostrongyles) (85.5%), liver flukes (Fasciola gigantica) (34.0%), coccidia (30.9%) and tapeworms (9.6%). Eight species of the protozoan Eimeria were identified, the most prevalent species being E. bovis and E. zuernii. The most prevalent nematode genera were Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus. Season, farm and age of the animals had a significant (p<0.05) influence on the intensity of infection with strongyles, liver flukes and coccidia, whereas the sex of the animals had no significant (p>0.05) effect on the prevalence or intensity of infections. A higher intensity of infection with strongyles and coccidia was found in the wet season than in the dry season (p<0.05). The age-specific intensity was in the following order: for strongyles, immature animals of 6–12 months of age had the highest egg counts, followed by young calves and adults. Calves had significantly (p<0.05) higher oocyst counts than immatures or adults. Liver fluke egg counts did not differ significant (p>0.05) between immatures and adult cattle.     

Up-regulation of Endothelin-1 and Endothelin type A receptor genes expression in the heart of broiler chickens versus layer chickens

To compare Endothelin (ET) production and genes expression of ET-1 and ET_A receptor (ET_AR) between broiler and layer chickens during rearing, semi-quantitative RT-PCR and enzyme immunometric assay were performed in the heart ventricles and serum. There were gradual elevations of ET-1 and ET_AR mRNAs in the left ventricle of broiler and layer chicken groups that were mainly significant (P < 0.05) at 28, 35 and 42 days of age with compared to previous days whereas were not significant between two groups.These gradual elevations of ET-1 and ET_AR mRNAs were also observed in the right ventricle that were significant (P < 0.05) at 28, 35 and 42 days of age in broilers and 42 days of age in layers with compared to previous days. Increasing of these mRNAs in the right ventricle of broiler chickens were significantly (P < 0.05) more than layer chickens at 28, 35 and 42 days. Serum ET in broilers was significantly (P < 0.05) higher than layer chickens at 28 and 42 days of age. It is concluded that circulating ET and cardiac ET-1, ET_AR genes expression is higher in broiler chickens than in layer chickens particularly after 21 days of age. It is probably that these breed differences make broiler chickens to be more susceptible to Endothelin related-cardiomyopathies such as congestive heart failure and ascites.     

常山散效力试验用虫株的敏感性

为进一步验证常山散的抗球虫效果以及效力试验用虫株的敏感性,在百球清为对照的基础上,对效力试验用虫株再次以三字球虫粉为对照进行试验.试验分为常山散组、三字球虫粉组、攻虫不给药组和不攻虫不给药组,分别从攻虫后24 h(球虫入侵)和72 h(裂殖发育)开始给药,攻虫后168 h停止给药,观察药物对鸡临床症状、血便排出、盲肠病...     

Effect of infection with mixed Eimeria species on T cells and T regulatory cell properties

An experiment was conducted to study the effect of a mixed Eimeria infection on chicken regulatory T cell (Treg) percentages, T-cell percentages, cell proliferation, and cytokine mRNA amounts. Specific-pathogen-free white leghorn birds were raised in battery cages and were challenged with and without coccidial oocysts at 21 d of age. At 6 d post challenge, birds inoculated with coccidial oocysts shed an average of 1.5 × 10⁴ oocysts/gram of feces. At d 6 post challenge, both CD4⁺ and CD8⁺ cell percentages in the cecal tonsil were significantly (P < 0.01) increased in challenged birds compared to the control. At d 11, CD4⁺ cell percentages in the cecal tonsil were higher in the control birds. At 6 d post challenge there was a 6-fold increase (P = 0.18) in IL-10 mRNA content in the cecal tonsils of infected birds compared to the control. At 11 d post challenge there was a 4-fold increase (P = 0.09) in IL-10 mRNA content in the infected birds’ cecal tonsils. At 11 d post challenge there was half as much (P = 0.10) IFN-γ mRNA content in the spleen of infected birds compared to the control. At 6 d post challenge, the CD25 depleted cecal tonsils of infected birds had increased proliferation (P < 0.05) compared to the control. It could be concluded that a mixed Eimeria infection causes an up-regulation of IL-10, Tregs, and CD4⁺ cells in the cecal tonsils during the late stages of infection.     

Emerging Technologies in Microbial Ecology Aid in Understanding the Effect of Monensin in the Diets of Broilers in Regard to the Complex Disease Necrotic Enteritis

Necrotic enteritis is a complex disease condition of broiler chickens, commercial layer pullets, and turkeys and requires the presence of a toxigenic strain of Clostridium perfringens, alteration of bird diets, and damage to the intestinal epithelium. All of these alone, but especially in combination, result in significant alterations of the intestinal microflora. The intestinal microflora is part of a complex ecosystem that is involved in augmenting intestinal development, immune surveillance, and competitive exclusion against pathogenic organisms. However, when the microflora fails to protect the mucosa from pathogens, antimicrobials are used to reduce the numbers of pathogenic organisms or to prevent their colonization of the intestine. We were interested in studying the effects of monensin on the bacterial community within the ileum of chickens because ionophore antimicrobials are commonly used to prevent Eimeria infections in broilers. We used two 16S ribosomal DNA community analysis protocols, terminal restriction fragment length polymorphism analysis combined with 16S rDNA clone libraries. These methods showed that monensin caused significant alterations in the microbial community structure of the ileum. Whereas the ileal bacterial community of control birds primarily consisted of lactobacilli, monensin-treated birds had communities rich in clostridia. None of the birds exhibited signs of intestinal disease or mucosal lesions, which suggested that the clostridia were avirulent. Although the therapeutic benefits of monensin may largely result from its anticoccidial effects, its ability to foster a competitively exclusive bacterial community may contribute to the intestinal health of birds, thus preventing the development of necrotic enteritis.