Research Note: Evaluation of dietary administration of sodium chlorate and sodium nitrate for Histomonas meleagridis prophylaxis in turkeys.

Histomoniasis is currently a re-emerging disease of major significance for many commercial turkey and broiler breeder production companies because of the unavailability of drugs or vaccines. The protozoa Histomonas meleagridis (HM) requires the presence of enteric microflora to promote the disease. The objectives of this research note were to evaluate the effect of dietary administration of sodium chlorate (SC) and sodium nitrate (SN) in vitro and in vivo for HM prophylaxis in poults. A total of 128 day-of-hatch female poults obtained from a commercial hatchery were wing-tagged and randomly assigned into 1 of 4 experimental groups: negative control (NC), positive control, dietary inclusion of SC (3,200 ppm) and SN (500 ppm). Poults from groups SC and SN started on their respective diets on day 12. All groups, except the NC, were challenged with 2 × 105 HM on day 19. Controls were fed a basal diet, identical to the treatment diets but not supplemented with SC or SN. Body weight gain (BWG) was determined weekly, starting on day 1 until day 28, and postchallenge morbidity and mortality were recorded. On day 28 of age, all surviving poults were lesion scored for hepatic and cecal lesions. Ceca and distal ileum were collected on day 28 for bacterial recovery on selective media for total aerobic, lactic acid bacteria, or gram-negative bacteria. The addition of SC and SN in the in vitro growth of HM greatly reduced the growth of the protozoa after 20 h of incubation when compared with the control nontreated group (P < 0.05). However, dietary supplementation of SC and SN had no effect against HM in vivo, as was demonstrated by BWG, the severity of lesions in the liver and ceca or bacterial recovery of treated poults when compared with the positive control group.

Effects of prophylactic antibiotic-treatment on post-surgical recovery following intraperitoneal bio-logger implantation in rainbow trout.

Bio-logging devices can provide unique insights on the life of freely moving animals. However, implanting these devices often requires invasive surgery that causes stress and physiological side-effects. While certain medications in connection to surgeries have therapeutic capacity, others may have aversive effects. Here, we hypothesized that the commonly prescribed prophylactic treatment with enrofloxacin would increase the physiological recovery rate and reduce the presence of systemic inflammation following the intraperitoneal implantation of a heart rate bio-logger in rainbow trout (Oncorhynchus mykiss). To assess post-surgical recovery, heart rate was recorded for 21 days in trout with or without enrofloxacin treatment. Contrary to our hypothesis, treated trout exhibited a prolonged recovery time and elevated resting heart rates during the first week of post-surgical recovery compared to untreated trout. In addition, an upregulated mRNA expression of TNFα in treated trout indicate a possible inflammatory response 21 days post-surgery. Interestingly, the experience level of the surgeon was observed to have a long-lasting impact on heart rate. In conclusion, our study showed no favorable effects of enrofloxacin treatment. Our findings highlight the importance of adequate post-surgical recovery times and surgical training with regards to improving the welfare of experimental animals and reliability of research outcomes.

Biological Approaches for Disease Control in Aquaculture: Advantages, Limitations and Challenges.

Although aquaculture activity has experienced a great development over the past three decades, infectious diseases have become a limiting factor for further intensification. Because the use of antibiotics has led to the widespread emergence of antibiotic resistance, the search for alternative environmentally friendly approaches is urgently needed. This Opinion paper offers an update on the successes and challenges of biological approaches for bacterial disease prevention and control in aquaculture. Although most of these approaches are still in research and development stages, some of them have shown promising results in field trials. Therefore, a better understanding of the mechanisms of action of these approaches will help to maximise their beneficial properties.

Nasal carriage of mecA-positive methicillin-resistant Staphylococcus aureus in pigs exhibits dose-response to zinc supplementation.

Zinc (Zn) is often supplemented at elevated concentrations in swine diets, particularly in piglets, to prevent enteric infections and promote growth. Previous studies from Denmark have suggested a genetic linkage and a phenotypic association between Zn resistance, encoded by czrC, and methicillin-resistance conferred by mecA in Staphylococcus aureus. Such an association has not been reported in the U.S. swine population. We conducted an analysis of the effects of Zn, supplemented as zinc oxide (ZnO), on the nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) in nursery (n=40) and finisher pigs (n=40) enrolled in a nutritional study. Nasal swabs, collected from nursery and finisher pigs, were inoculated onto MRSA CHROMagar and presumptive MRSA colonies were tested for the presence of mecA and czrC genes by polymerase chain reaction. Zinc susceptibility was determined by the agar dilution method. The prevalence of mecA-positive MRSA was 10% (4/40) and 20% (8/40) among nursery and finisher pigs, respectively. Of the 12 mecA-positive S. aureus isolates, 7 had the czrC gene (58.3%) compared to none among the 68 mecA-negative isolates. The presence of both mecA (p=0.002) and czrC (p=0.006) genes were positively associated with higher levels of Zn supplementation. The median minimum inhibitory concentrations of Zn for czrC-positive and czrC-negative isolates were 12 and 2 mM, respectively (p<0.0001). The link between czrC and mecA genes suggests the importance of elevated Zn supplementation in the co-selection and propagation of methicillin resistance among S. aureus in pigs.

Prophylactic administration of a combined prebiotic and probiotic, or therapeutic administration of enrofloxacin, to reduce the incidence of bacterial chondronecrosis with osteomyelitis in broilers.

Bacteria entering the bloodstream via translocation from the gastrointestinal tract spread hematogenously and can trigger bacterial chondronecrosis with osteomyelitis (BCO) by infecting osteochondrotic microfractures in the epiphyseal-physeal cartilage of the proximal femora and tibiae. In experiment 1, broilers were fed control feed or the same feed containing BacPack 2X, which includes the prebiotic IMW50 (a mannan oligosaccharide beta-glucan yeast cell wall product) plus the probiotic Calsporin (Bacillus subtilis C-3102). Broilers reared on wire flooring consistently developed higher incidences of BCO than hatchmates reared on wood shavings litter (≥24 vs. ≤4%, respectively; P=0.001). Adding BacPack 2X to the feed on d 1 through 56 delayed the age of onset and reduced the cumulative incidence of BCO on wire flooring when compared with broilers fed the control feed (24.0 vs. 40.7%, respectively; P=0.003). In experiment 2, broilers reared on wire flooring received tap water on d 1 through 62 (control group) or therapeutic levels of the potent fluoroquinolone antimicrobial enrofloxacin in the water on d 35 through 54 (enrofloxacin group). During enrofloxacin administration, half as many birds developed BCO in the enrofloxacin group when compared with the control group (8.1 vs. 19.5%, respectively, on d 35 through 54; P=0.001), whereas both groups had similar BCO incidences subsequent to withdrawing enrofloxacin on d 55 through 62 (14.8 vs. 18.2% for the enrofloxacin vs. control groups; P=0.386). Cumulative lameness incidences for d 1 through 62 were higher for the control group than for the enrofloxacin group (39.0 vs. 25.8%, respectively; P=0.003). These results demonstrate that wire flooring imposes a rigorous challenge that leads to high incidences of BCO that can be difficult to suppress, even with therapeutic doses of enrofloxacin. Prophylactically adding BacPack 2X to the feed reduced the incidence of BCO lameness by a proportion similar to that achieved with enrofloxacin, indicating that probiotics potentially can provide effective alternatives to antibiotics for reducing BCO lameness attributable to bacterial translocation and hematogenous distribution.

Decreased mortality of weaned pigs with Streptococcus suis with the use of in-water potassium penicillin G.

This study evaluated the efficacy of potassium penicillin G in drinking water of weaned pigs to reduce mortality and spread of infection caused by Streptococcus suis. A total of 896 18-day-old weaned pigs were randomly assigned to either treatment with potassium penicillin G in-water (Treated), or no treatment (Control). The outcomes analyzed were total mortality, mortality due to S. suis, and overall counts of S. suis colonies. The risk of mortality due to S. suis and total mortality were significantly increased in the Control group compared with Treated pigs (P < 0.05). Bacterial culture of posterior pharyngeal swabs indicated that Control pigs were significantly more likely to have ≥ 1000 colonies of S. suis per plate than were Treated pigs (P < 0.05). This study demonstrates that potassium penicillin G administered in drinking water is effective in reducing mortality associated with S. suis infection and reducing tonsillar carriage of S. suis.

Chemoprophylactic effects of azithromycin against Rhodococcus equi-induced pneumonia among foals at equine breeding farms with endemic infections.

OBJECTIVE: To determine the effect of azithromycin chemoprophylaxis on the cumulative incidence of pneumonia caused by Rhodococcus equi, age at onset of pneumonia, and minimum inhibitory concentration (MIC) of azithromycin for R equi isolates cultured from fecal and clinical samples. DESIGN: Controlled, randomized clinical trial. ANIMALS: 338 foals born and raised at 10 equine breeding farms; each farm had a history of endemic R equi infections. PROCEDURES: Group 1 foals were control foals, and group 2 foals were treated with azithromycin (10 mg/kg [4.5 mg/lb], PO, q 48 h) during the first 2 weeks after birth. Foals were monitored for development of pneumonia attributable to R equi infection and for adverse effects of azithromycin. Isolates of R equi were tested for susceptibility to azithromycin. RESULTS: The proportion of R equi-affected foals was significantly higher for control foals (20.8%) than for azithromycin-treated foals (5.3%). Adverse effects of azithromycin treatment were not detected, and there were no significant differences between groups for the MICs of azithromycin for R equi isolates cultured from fecal or clinical samples. CONCLUSIONS AND CLINICAL RELEVANCE: Azithromycin chemoprophylaxis effectively reduced the cumulative incidence of pneumonia attributable to R equi among foals at breeding farms with endemic R equi infections. There was no evidence of resistance to azithromycin. Nonetheless, caution must be used because it is possible that resistance could develop with widespread use of azithromycin as a preventative treatment. Further investigation is needed before azithromycin chemoprophylaxis can be recommended for control of R equi infections.

A clinical trial evaluating prophylactic and therapeutic antibiotic use on health and performance of preweaned calves.

The objective of this clinical trial was to evaluate the influence of prophylactic and therapeutic antibiotics on health and performance in preweaned dairy calves on a calf ranch. One hundred twenty 1-d-old calves were enrolled into 3 management systems for antibiotic use and raised until 4 wk of age. Sixty calves were not eligible to receive prophylactic or therapeutic antibiotics. Thirty calves were eligible to receive individual antibiotic treatment for disease, but no prophylactic antibiotics in milk replacer. The remaining 30 calves received milk replacer medicated with neomycin and tetracycline HCl, and could be treated with antibiotics. Health status and treatments were monitored and recorded daily. The primary study outcomes were weight gain, morbidity, and mortality. The most important factor associated with morbidity and mortality was passive immune transfer through colostrum. In-feed antibiotics delayed onset of morbidity, decreased overall morbidity, and increased weight gain. Nonantibiotic therapies for clinical disease were associated with increased mortality and morbidity compared with antibiotic treatments. The study has shown that minimizing or eliminating the use of antibiotics in the feed requires measures to ensure adequate passive transfer of immunity, but that in the face of inadequate passive transfer of immunity, animal welfare may be endangered by replacing medicated milk replacer with nonmedicated milk replacer, and therapeutic antibiotics with nonantibiotic alternatives.

Differences in antibiotic resistance in Escherichia coli, isolated from East-European swine herds with or without prophylactic use of antibiotics.

The aim of the study was to compare the resistance patterns of Escherichia coli isolates from pig herds with or without prophylactic use of anti-microbial substances. The presented pig units received either antibiotics or oregano as preventive feed additives. The trial was performed from April to October 2001, in the large 'country-corner', Hungary-Rumania-Serbia. Thirty of 39 evaluated herds suffered E. coli O139 K88 ac or ad LT STb caused losses, the remaining were negative for E. coli O139. Thirteen of the selected 30 herds produced with oregano feed supplementation (Oregpig Pecs, Hungary) antibiotic-free pigs. These units had no history of prophylactic antibiotic use since 1995. The remaining 17 herds routinely used prophylactic antibiotic feed supplementation. In each herd, pigs of four different age groups (suckling piglets, weaners. fattening swine and breeding sows), showing the clinical symptoms of wasting, were investigated. E. coli O139 K88 ac or ad LT STb were tested for their resistance to antibiotics, available in this region. Oregano-fed herds demonstrated high significantly (P < 0.001) lower MICs (microg/ml) for ampicillin, doxycyclin, enrofloxacin, gentamycin, oxytetracyclin and sulfamethacin compared to herds with prophylactic use of antibiotics. Resistance to ceftiofur revealed significant (P < 0.05) differences between the antibiotic- or oregano-treated units. The present results confirm literature data, that prophylactic use of antibiotics likely plays a role in inducing resistance of E. coli and other intestinal bacteria. Thus, imposing greater restrictions on antibiotic use in animal agriculture is likely to reduce but not eliminate the occurrence of resistant isolates.

Comparison of the supplemental effects of Saccharomyces cerevisiae and antibiotics in low-protein and high-fibre diets fed to broiler chickens.

Two experiments were completed to compare the supplemental effects of yeast Saccharomyces cerevisiae and sub-therapeutic antibiotics in high-fibre and low-protein diets for broiler chicks. In experiment 1, yeast was added at 1.5, 3.0 and 6.0 g kg-1 while penicillin, tylosin or neoterramycin were added at 150 mg kg-1 into different batches of a high-fibre diet containing 250 g kg-1 palm kernel meal. Saccharomyces cerevisiae and antibiotics increased BW, BWG, FCR, feed intake, carcass and breast weights above the control. Small intestine weight was reduced by antibiotics, while yeast caused a lower deposition of abdominal fat. Liver weights of different treated broilers were similar. The performance indices were superior on penicillin and 3.0 g kg-1 yeast compared to other supplements evaluated. In the second experiment, 1.5 and 3.0 g kg-1 of yeast, and 0.75 mg kg-1 of procaine penicillin, zinc bacitracin and tylosin were separately added to a 180 g kg-1 crude protein diet. Performance of the chicks with additives was compared with unsupplemented negative and positive controls containing 180 and 210 g kg-1 crude protein respectively. Broilers fed with supplements had superior BW, BWG, FCR and feed intake compared to the negative control, but carcass data were similar. Dietary penicillin increased BW, BWG, feed intake more than other supplements, but yeast stimulated higher FCR. Data from both studies indicated that Saccharomyces cerevisiae comparatively increased growth and carcass weight and reduce abdominal fat, therefore, it can serve as a natural substitute for antibiotics in broiler diet.

Surgical treatment of gastric leiomyoma in a dog.

A 12-year-old entire male Maltese terrier was presented with a 1 month history of vomiting and haematemesis. Microcytic hypochromic anaemia was detected. Abdominal radiography, ultrasonography and gastric endoscopy identified a discrete intramural mass in the pyloric antrum. An ulcerated leiomyoma was removed by a partial-thickness intraluminal resection of the gastric wall. The dog recovered well and is free from clinical signs 20 months after surgery.

Control of proliferative enteropathy in growing/fattening pigs using growth promoters.

The aim of this study was to evaluate the effect of different antibiotics used as growth promoters on the control of porcine intestinal adenomatosis when administered in weaning, growing and fattening pig diets, according to Annex I of the European Union directive (70/524/EEC and its subsequent amendments to date) for the use of feed additives. On a farm with a previous history of proliferative enteropathy outbreaks, 648 weaned piglets (23 days old) were divided into nine experimental groups according to bodyweight and sex ratio, each group comprising four pens with 18 pigs in each pen. One group served the trial as a negative (unmedicated) control: another (the positive control) received monensin via feed at 100 p.p.m. up to the end of the growing phase (107 days old) and 50 p.p.m. up to slaughter age (156 days old). The remaining seven groups were offered feed with the addition of the following antibiotics: virginia-mycin (50-20 p.p.m.), avilamycin (40-20 p.p.m.), spiramycin (50-20 p.p.m.), zinc bacitracin (50-10 p.p.m.), avoparcin (40-20 p.p.m.), tylosin (40-20 p.p.m.) and salinomycin (60-30 p.p.m.), respectively. The performance of the pigs in the positive control group was very satisfying and among the highest in the trial, verifying earlier field studies. As a general conclusion it seems that all tested growth promoters had a beneficial effect compared with the untreated control, indicated by the decrease of mortality rate, the elimination of diarrhoeal incidence and the enhancement of growth performance, although the proliferative enteropathy control achieved by each substance was not always satisfactory. More specifically, the antibiotic growth promoters tested can be scaled according to their total efficacy as follows: 1. Salinomycin, tylosin, spiramycin; 2. Virginiamycin, zinc bacitracin, avilamycin; and 3. Avoparcin. Finally, it is considered that part of the growth promotion efficacy of the tested substances is due to their potential capacity to control porcine intestinal adenomatosis; thus, in future growth performance trials, the disease background of the trial farms must be examined, especially for porcine enteropathy challenges.

Effect of feeding diets containing an antibiotic, a probiotic, or yucca extract on growth and intestinal urease activity in broiler chicks.

A 6-wk study was conducted to determine the effect of feeding diets containing an antibiotic, a probiotic, or yucca extract on daily gain, feed conversion ratio, and urease activity and ammonia production in intestinal contents of broiler chicks. Four replicates of 10 broiler chicks (average body weight, 48 g) each were assigned to a control or diets containing 0.1% chloroxytetracycline (antibiotic), 0.1% Lactobacillus casei (probiotic), or 0.2% yucca extract. Feeding a diet containing the probiotic significantly (P < 0.05) increased average daily gain during the first 3-wk period compared to the control (30.7 vs 28.7 g). This increase was partly accounted for by increased feed intake. During the first 3 wk, feeding the diet containing probiotic significantly (P < 0.05) decreased urease activity (per gram of collected contents) in small intestinal contents but not in large intestinal contents, compared with the control. Urease activity determined at 6 wk of age was not significantly affected by diet. Our studies indicate that dietary probiotic decreases urease activity in the small intestinal contents of young chicks and thus may be beneficial for improving animal health and growth, especially during early life.