Medicated Feed Research Articles

In vivo therapeutic potentiality of red seaweed, Asparagopsis (Bonnemaisoniales, Rhodophyta) in the treatment of Vibriosis in Penaeus monodon Fabricius

The crude extract of the red seaweed, Asparagopsis sp. was evaluated for in vivo antibacterial activity against the shrimp vibrio pathogens. The algal extract was rationalized with commercial shrimp feed and orally administered for different duration of time followed by the artificial bacterial challenge experiment. In dose titration experiments, the oral administration of Asparagopsis sp. at a dosage of 850mgkg–1 of biomass was highly efficacious in the treatment of natural infestations of Vibriosis in Penaeus monodon. The results of the confirmatory dose experiment revealed that the prophylactic treatment with moderate dose of 850mgkg–1 of biomass day–1 for four weeks followed by 14 days of post infection therapy was highly effective in controlling Vibrio infection in shrimps. Moreover, results of the percent survival index and microbiological analysis clearly show that Asparagopsis extract incorporated medicated feed had broad therapeutic potential for managing shrimp Vibriosis. In addition, in vivo trials and results obtained in this work are based on the crude organic extract sourced from an unidentified Asparagopsis cryptic lineage, therefore further molecular analysis to identify the species will be required.

Detection, Accumulation, Distribution, and Depletion of Furaltadone and Nifursol Residues in Poultry Muscle, Liver, and Gizzard

Nitrofurans were broadly used as an extremely effective veterinary antibiotic especially in pig and poultry production farms. Because of fears of the carcinogenic effects on humans, the nitrofurans were banned from use in livestock production in many countries, including the European Union. The present study examines the accumulation, distribution, and depletion of furaltadone and nifursol and of their tissue-bound metabolites [3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ) and 3,5-dinitro-salicylic acid hydrazine (DNSAH), respectively, in poultry edible tissues (muscle, liver, and gizzards) following administration to chickens of therapeutic and subtherapeutic concentrations of both compounds. Nitrofurans determination was performed by high-performance liquid chromatography-diode array detection and liquid chromatography-tandem mass spectrometry, respectively, for feeds and for poultry tissues. Furaltadone and nifursol, in very low concentrations, were found in samples of muscle, liver, and chicken's gizzard collected from slaughtered animals after 5 weeks of treatment and no withdrawal time period. When a withdrawal time period of 3 weeks was respected, no detectable nitrofuran parent compounds was observed in all of the studied matrices. For AMOZ, concentrations of 270 μg/kg in meat, 80 μg/kg in liver, and 331 μg/kg in gizzard were determined after administration of a medicated feed with furaltadone (132 mg/kg), 3 weeks after withdrawal of treatment. For DNSAH, the concentration values obtained are much lower than those observed for AMOZ. For meat, liver, and gizzard, DNSAH concentrations of 2.5, 6.4, and 10.3 μg/kg, respectively, were determined, after administration of a medicated feed with nifursol (98 mg/kg), 3 weeks after withdrawal of treatment. The gizzard could be considered a selected matrix for nitrofuran residues evaluation in poultry, due to its capacity of retaining either nitrofuran parent compounds or metabolites in higher concentrations, regardless of the administered dose or of the respected withdrawal time period.

Elimination of Chloramphenicol in Rainbow Trout Receiving Medicated Feed

Chloramphenicol muscle residue levels in rainbow trout were determined after oral administration of 84 μg kg-1d-1 of chloramphenicol for four days. Samples were taken one day before treatment and for 43 days after the treatment was over. Chloramphenicol was analysed using an in-house enzyme linked immunoassay (ELISA) validated against the criteria of the Commission Decision 2002/657/EC. Validation parameters confirmed that the method was appropriate for the detection of chloramphenicol at levels below the minimum required performance limit (MRPL) of 0.3 μg kg-1. The highest chloramphenicol levels were observed on the first day after the treatment had ended (144.3 μg kg-1). Elimination was significant over the first seven days; significant differences were detected between days 1 and 3 (p<0.001), 3 and 5 (p<0.001), and 5 and 7 (p<0.05). Chloramphenicol levels dropped below MRPL to 0.17 μg kg-1 on day 9 after the end of treatment. From day 11 to 43, chloramphenicol residues were detectable in a range from 0.091 μg kg-1 (highest) to 0.011 μg kg-1 (lowest). Our results indicate that trout muscle tissue could be compliant with health requirements for consumption 10 days after withdrawal from chloramphenicol treatment.

Efficacy of marine green alga Ulva fasciata extract on the management of shrimp bacterial diseases

Secondary metabolites of the green algae, Ulva fasciata, were tested to determine the efficacy of controlling shrimp bacterial pathogens. Exploratory experiments indicated that an intermediate dose (1 g kg -1 of shrimp) of Ulva in the diet was highly effective at controlling bacterial pathogens of shrimp, as compared to lower (500 mg kg -1 ) and higher (1.5 g kg -1 ) doses. The pilot experiments evaluated the percent of relative protection afforded shrimps treated with Ulva diet and faced with various concentrations of bacterial pathogen. The survival of shrimps treated with Ulva diet was significant (P < 0.01). The present findings indicate that the green U. fasciata may be an excellent source for developing a potent medicated feed for shrimp disease management.

Penetration of oxytetracycline into the nasal secretions and relationship between nasal secretions and plasma oxytetracycline concentrations after oral and intramuscular administration in healthy pigs

The penetration of oxytetracycline (OTC) in plasma and nasal secretions of healthy pigs was evaluated during the first study, in response to oral dose of 20 mg of OTC per kg of body weight (bwt) per day as a 400 mg/kg feed medication (n = 5) and to intramuscular (i.m.)-administered formulations at 10 mg/kg bwt (n = 5), 20 mg/kg bwt (n = 5), 40 mg/kg bwt (n = 5). Concentrations of OTC in plasma and nasal secretions were determined by a validated ultra-high performance liquid chromatography associated to tandem mass spectrometry method (UPLC/MS/MS). The objectives were to select the efficacy treatment and to evaluate the possibility to predict nasal secretions concentrations from those determined in plasma. The animals were housed together in each experiment. In each group, the treatment was administered once daily during 6 consecutive days, and nasal secretions and plasma were collected after 4 and 24 h at day 2 and day 6. For oral administration, only one medicated feed was prepared and distributed to all the animals together and was consumed in approximately 1 h. To meet recommendations of efficacy for OTC in nasal secretions, only the i.m. of 40 mg/kg bwt associated to an inter-dosing interval of 24 h provides and maintains concentrations in nasal secretions ≥1 μg/mL, appropriate to the MIC 50 and 90 of Pasteurella multocida and Bordetella bronchiseptica, respectively, the main pathological strains in nasal secretions. It has been demonstrated that, using a generalized linear mixed model (GLMM), OTC in the nasal secretions (μg/mL) can be predicted taking into account the OTC concentrations in plasma (μg/mL), according to the following equation: OTC(nasal secretions) = 0.28 OTC(plasma) -1.49. In a second study, the pharmacokinetic behaviour of OTC in plasma and nasal secretions of healthy pigs was investigated, after single-dose i.m. of 40 mg/kg bwt of the drug. Blood samples and nasal secretions were collected at predetermined times after drug administration. The data collected in 10 pigs for OTC were subjected to non-compartmental analysis. In plasma, the maximum concentration of drug (C(max) ), the time at which this maximum concentration of drug (T(max) ) was reached, the elimination half-life (t½) and the area under the concentration vs. time curve (AUC) were, respectively, 19.4 μg/mL, 4.0, 5.1 h and 150 μg·h/mL. In nasal secretions, C(max) , T(max) , t½ and AUC were, respectively, 6.29 μg/mL, 4.0, 6.6 h and 51.1 μg·h/mL.

Detection of lasalocid residues in the tissues of broiler chickens by a new screening test total antibiotics

The aim of the present study was to evaluate the microbial growth inhibition test Total antibiotics for the screening of lasalocid residues in the tissues of broiler chickens after its oral administration in medicated feed. The residues were investigated throughout the 5-day withdrawal period /WP/) and also on day 6 representing the first day following the WP. All broiler chicken tissues were positive for lasalocid. The breast muscle was positive (the presence of residues at/above the detection limit /LOD/ of method) up to day 1 of the WP, the thigh muscle, gizzard, heart, skin and fat up to day 3 of the WP and the liver and kidneys up to day 4 of the WP. When evaluating the dubious results (the presence of residues just below the LOD of method), the breast muscle was suspect positive up to day 3 of the WP and the gizzard, skin and fat up to day 4 of the WP. No positive or dubious results were detected on day 5 of the WP. The LOD of Bacillus stearothermophilus var. calidolactis for maduramycin was 500 µg.l-1.

Development and pharmacokinetic evaluation of erythromycin lipidic formulations for oral administration in rainbow trout ( Oncorhynchus mykiss)

The aim of this work was to enhance the bioavailability of erythromycin base when administered orally in rainbow trout ( Oncorhynchus mykiss). Since erythromycin is normally given in the form of medicated feed, in this study three new types of feed formulation were developed. A self-emulsifying system and two types of double microemulsions (O/W/O) were prepared, characterized and adsorbed on a commercial extruded diet for fish. The emulsified systems were based on saturated polyglycolized glycerides and mono- and diglycerides of medium-chain fatty acids (as oily phase), Tween® 80 (as surfactant) and, in the case of double microemulsions, distilled water. The systems differed in percentage composition and for the amount and position of erythromycin in different phases. The three medicated feed were then administered orally by means of a gastric probe to rainbow trout and their relative bioavailability was estimated in comparison with that obtained after oral administration of feed with erythromycin powder. For each medicated feed, 80 fish were tested. Finally, plasma profiles of erythromycin after single administration of medicated feeds were used to predict profiles obtainable by administering once-daily medicated feeds for 7 consecutive days. The results proved that the feeds containing microemulsified erythromycin provided largely superior oral bioavailability and the advantage of obtaining the same efficacy against bacterial infections with a much lower dose of drug.

Oleuropein using as an Additive for Feed and Products used for Humans

Olive tree has been accepted as a symbol of holiness, abundance, wisdom and health, for centuries. Although its fruit is mainly used as a food after processing for table olive and olive oil, it is used for preparing medical products, cosmetic and animal feed. Olive trees have been cultivated for thousands of years, but the immune and circulatory benefits of olive leaf have only recently become fully realized. Olive leaf was first used medicinally in Ancient Egypt and was a symbol of heavenly power. There are many in vivo and in vitro researhes has been done on the effects of Oleuropein, one of the most important phenolic compound extracted from olive leaves, on health. The effects of the olive tree, accepted as an elixir of health and especially its product Oleuropein on human health and as an additive for animal feeds.

Preparation of Ormetoprim–Sulfadimethoxine‐Medicated Discs for Disc Diffusion Assay

AbstractRomet (a blend of ormetoprim and sulfadimethoxine) is a type A medicated article for the manufacture of medicated feed in the catfish industry. Recently, the commercial manufacture of ormetoprim–sulfadimethoxine susceptibility discs was discontinued. Ormetoprim–sulfadimethoxine discs were prepared at the Mississippi State University College of Veterinary Medicine Aquatic Diagnostic Laboratory according to Clinical and Laboratory Standards Institute guidelines. The performance of the laboratory‐prepared discs was compared with that of commercially prepared discs in disc diffusion assays with 23 field isolates of Edwardsiella ictaluri. The a priori limits of agreement for the laboratory‐prepared ormetoprim–sulfadimethoxine discs were ±5 mm of the zones for the commercial discs. The resulting zones of inhibition ranged from 33 to 50 mm and from 35 to 52 mm for the laboratory‐prepared and commercially prepared discs, respectively. The data comparing the two sets of discs were analyzed to determine the level of agreement. The analysis demonstrated that the laboratory‐prepared discs produced a slightly smaller zone of inhibition than the commercially prepared ones. The observed limits of agreement were within the a priori established limits of agreement, indicating that the laboratory‐prepared ormetoprim–sulfadimethoxine discs were acceptable replacements for the commercially prepared discs.Received April 21, 2010; accepted June 29, 2010

Effectiveness of Aquaflor (50% Florfenicol) to Control Mortality Associated with Streptococcus iniae in Freshwater‐Reared Subadult Sunshine Bass

We conducted a field trial to evaluate the effectiveness of Aquaflor (50% florfenicol) for controlling mortality associated with Streptococcus iniae in freshwater-reared subadult sunshine bass (female white bass Morone chrysops X male striped bass M. saxatilis). Bacterial samples collected from moribund fish representing a reference population were presumptively identified microbiologically and were later confirmed to be S. iniae by biochemical characterization and polymerase chain reaction. The trial comprised a 1-d acclimation period, 10-d treatment period, and 14-d posttreatment period. During the treatment period, Aquaflor-medicated feed was administered to treated tanks (N = 3) at a target dose of 10 mg of florfenicol x kg of fish(-1) x d(-1), and nonmedicated feed was administered to control tanks (N = 3). At the end of the posttreatment period, mean (+/- SD) cumulative mortality in treated tanks (9 +/- 11%) was significantly (P = 0.040) less than that in control tanks (52 +/- 13%). Analysis of medicated feed samples revealed that treated tanks had received an actual dose of 8.3 mg florfenicol x kg fish(-1) x d(-1) (83% of target). No florfenicol was detected in control feed samples. Although the actual florfenicol dose administered to treated tanks was less than the target dose, the trial was accepted by the U.S. Food and Drug Administration Center for Veterinary Medicine as demonstrating the efficacy of Aquaflor to control mortality associated with S. iniae in cultured sunshine bass populations.

Feed intake and tissue distribution of florfenicol in cod (Gadus morhua) administered feed with different fat contents

Summary This study was performed to examine the appetite and the corresponding plasma and tissue distribution of florfenicol when administered to healthy groups of cod using medicated and non-medicated salmonid and marine feeds. Marine feed contains approximately 18% fat whereas salmonid feed contains approx. 30% fat. Two groups of fish were medicated with florfenicol at a dosage of 10 mg kg−1 day−1 for 10 consecutive days when the drug was administered either via marine or salmonid pellets. Two groups of fish also received either non-medicated marine or salmonid pellets. Twenty-four hours after giving the medicated marine feed, 14 out of 20 fish contained detectable concentrations of florfenicol with mean values (n = 14) of 4.67 ± 4.02 μg ml−1 in plasma, 2.29 ± 2.11 μg g−1 in muscle and 0.79 ± 0.69 μg g−1 in the liver. In the fish given medicated salmonid feed, 18 of 20 fish contained detectable concentrations of florfenicol with mean values (n = 18) of 1.77 ± 1.84 μg ml−1 in plasma, 0.75 ± 0.66 μg g−1 in muscle and 0.30 ± 0.25 μg g−1 in the liver. Decreased feed intake of the salmonid feed, both medicated and non-medicated, was noted when compared to medicated and non-medicated marine feed. No difference in feed consumption was registered between medicated and non-medicated marine feed, however a difference was noted between the medicated and non-medicated salmonid feed.

Effectiveness of Early Intervention with Florfenicol on a Streptococcus iniae Infection in Blue Tilapia

AbstractA study was performed to assess the efficacy of feeding a florfenicol (FFC)‐medicated diet to control experimental Streptococcus iniae infection in blue tilapia Oreochromis aureus. Tested doses of FFC were 0, 5, 10, 15, and 30 mg of active ingredient per kilogram of fish body weight (BW) per day. Fish were subjected to waterborne S. iniae exposure after skin scraping, and administration of medicated feed started at 6 h postchallenge and continued for 10 consecutive days, followed by a 12‐d posttreatment observation period. Administration of FFC‐medicated feed for 10 d significantly increased (P &lt; 0.05) the survival of S. iniae‐infected blue tilapia from 19% in the challenged, nonmedicated positive control group to 94, 96, 99, and 98% in the 5‐, 10‐, 15‐, and 30‐mg/kg FFC treatment groups, respectively. The survival rates of the different FFC‐medicated treatment groups were not significantly different. At the conclusion of the experiment, no S. iniae carriers were detected in any challenged group receiving the FFC‐medicated diet, while the bacterium was recovered from the S. iniae‐challenged, nonmedicated survivors of the infection. This study suggests that using FFC at 10 mg/kg BW daily for 10 d is an effective treatment against S. iniae infection in blue tilapia.

Depletion of veterinary drugs used in aquaculture after administration in feed to gilthead seabream (Sparus aurata).

This study was conducted to evaluate the depletion of residues of the antibiotics flumequine, oxytetracycline, sulfadiazine, trimethoprim, and oxolinic acid after in-feed administration to gilthead seabream. Fish were treated with the target antibiotics at doses of 30 mg/kg of body weight per day for 10 days at two seawater temperatures. Fish in each of five tanks were fed with a different medicated feed. After in-feed administration, five fish were randomly selected at different times, and antibiotic presence was analyzed in a mixture of muscle and skin. Antibiotic concentrations were determined through a validated analytical method based on liquid chromatography separation and mass spectrometry detection. Two trials were carried out with fish at different temperatures (14.0 and 19.5°C). Depletion of antibiotics occurred more rapidly at the higher temperature. Elimination rates for all antibiotics assayed were high, which indicates that the withdrawal period for these antibiotics could be reduced. The results suggest that in gilthead seabream maintained at these two temperatures no detectable concentrations of the antibiotics used in this study will remain in edible tissues 35 days after treatment. For flumequine and oxolinic acid, the elimination time is shorter (4 and 20 days, respectively).

Determination of Florfenicol Dose Rate in Feed for Control of Mortality in Nile Tilapia Infected with Streptococcus iniae

A dose titration study was conducted to determine the dosage of florfenicol (FFC) in feed to control Streptococcus iniae-associated mortality in Nile tilapia Oreochromis niloticus. Six tanks were assigned to each of five treatments: (1) not challenged with S. iniae and fed unmedicated feed; (2) challenged with S. iniae by injection and fed unmedicated feed; (3) challenged with S. iniae and given FFC at 5 mg/kg of body weight (bw) in medicated feed; (4) challenged with S. iniae and given 10 mg FFC/kg bw; and (5) challenged with S. iniae and given 15 mg FFC/kg bw. Treatment was initiated the day after inoculation, and feed was administered for 10 d. Cumulative mortality was 0% in the unchallenged, untreated group; 35.8 +/- 4.4% (mean +/- SE) in the challenged, unmedicated group; 19.2 +/- 2.7% in the 5-mg/kg treated group, 12.5 +/- 3.8% in the 10-mg/kg group, and 2.5 +/- 1.1% in the 15-mg/kg group. The cumulative mortality was significantly less in each challenged, FFC-treated group than in the challenged, unmedicated controls (5 mg/ kg: P = 0.0156; 10 mg/kg: P = 0.0007; 15 mg/kg: P < 0.0001). The efficacy of the 10- and 15-mg/kg FFC dosages was studied in a separate dose confirmation study. Fish in all tanks were injected with S. iniae. At 4 h postinoculation, 10 tanks were assigned to each of three feed treatments: (1) unmedicated feed; (2) 10 mg FFC/kg bw; and (3) 15 mg FFC/kg bw. Cumulative mortality was 20.5 +/- 2.0% in the challenged, unmedicated group; 11.0 +/- 2.1% in the 10-mg/kg group; and 5.5 +/- 2.4% in the 15-mg/kg group. Mortality was significantly less in the medicated groups than in the challenged, unmedicated control group (10 mg/kg: P = 0.0270; 15 mg/kg: P = 0.0007). Fish in both studies were necropsied, cultured for bacteria, and examined for gross lesions. The minimum inhibitory concentration of FFC against S. iniae in both studies ranged from 0.5 to 1.0 microg/mL. Florfenicol was palatable, safe, and efficacious for control of Nile tilapia mortality due to S. iniae infection.

Influence of a pig respiratory disease on the pharmacokinetic behaviour of amoxicillin after oral ad libitum administration in medicated feed

The pharmacokinetic properties of amoxicillin in healthy and respiratory-diseased pigs were studied, after ad libitum administration of medicated feed. In addition, amoxicillin dose linearity and drug penetration into respiratory tract tissues were evaluated in diseased animals. The respiratory disease involves porcine reproductive and respiratory syndrome virus and bacterial agents such as Pasteurella multocida, Bordetella bronchiseptica and Streptococcus suis. Typical clinical signs and gross lesions of respiratory disease were observed. The plasma pharmacokinetic analysis was performed by means of a noncompartmental approach. After single intravenous bolus administration of amoxicillin to healthy pigs, the steady-state volume of distribution was 0.61 L/kg, the total plasma clearance was 0.83 L/h/kg and the mean residence time was 0.81 h. After oral bolus administration, the mean absorption time was 1.6 h and the peak plasma concentration (3.09 μg/mL) reached at 1.1 h postadministration. The oral bioavailability was 34%. For oral ad libitum administration, plasma concentration-time profiles were related to the feeding behaviour. Plasma concentrations at steady-state were established between 12 and 120 h. The pharmacokinetic parameters calculated (C(maxss) , C(minss) , C(avss) and AUC(24ss) ) showed significantly lower values in healthy pigs compared to diseased animals. This was in accordance with the significantly higher amoxicillin bioavailability (44.7% vs. 14.1%) and longer absorption period observed in diseased pigs. Amoxicillin dose linearity in diseased animals was established in a dose range of 4-18 mg/kg. On the other hand, tissue distribution ratio in diseased animals was 0.65 for bronchial mucosa, 0.48 for lung tissue and 0.38 for lymph nodes. Our results suggest that the pharmacokinetic properties and disposition of amoxicillin can be influenced by the disease state or by related factors such as changes in the gastrointestinal transit.

In Vitro and In Vivo Efficacy of Florfenicol for Treatment of Francisella asiatica Infection in Tilapia

Francisella asiatica is a recently described, Gram-negative, facultative intracellular fish pathogen, known to be the causative agent of francisellosis in warm-water fish. Francisellosis outbreaks have increased in frequency among commercial aquaculture operations and have caused severe economic losses in every case reported. The lack of effective treatments for piscine francisellosis led us to investigate the potential efficacy of florfenicol for inhibition of F. asiatica in vitro and as an oral therapeutic agent in vivo. The MIC of florfenicol for F. asiatica, as determined by the broth dilution method, was 2 μg/ml, which indicates its potential efficacy as a therapeutic agent for treatment of francisellosis. The intracellular susceptibility of the bacterium to florfenicol in tilapia head kidney-derived macrophages (THKDM) was also investigated. Addition of florfenicol to the medium at 10 μg/ml was sufficient to significantly reduce bacterial loads in the THKDM in vitro. Cytotoxicity assays done in infected THKDM also demonstrated drug efficacy in vivo, as determined by lactate dehydrogenase (LDH) release. Levels of LDH released from infected THKDM were significantly lower in macrophages treated with florfenicol (P < 0.001) than in untreated cells. In medicated-feed trials, fish were fed 15 mg of florfenicol/kg of fish body weight for 10 days, and the feeding was initiated at either 1, 3, or 6 days postchallenge. Immersion challenges resulted in 30% mean percent survival in nontreated fish, and fish receiving medicated feed administered at 1 and 3 days postinfection showed higher mean percent survival (100% and 86.7%, respectively). A significant decrease (P < 0.001) in bacterial numbers (number of CFU/g of spleen tissue) was observed in treated groups compared to nontreated infected fish at both 1 and 3 days postchallenge. There were no differences in bacterial burden in the spleens between fish treated 6 days postchallenge and untreated controls. In conclusion, if florfenicol is administered during early stages of infection, it has the potential for effectively treating piscine francisellosis, including the capacity for intracellular penetration and bacterial clearance.

In-feed macrolide Leucomycin (Leucomag 30% PR) for prevention of proliferative enteropathy in experimentally infected pigs

The aim of this study was to evaluate the efficacy of orally administered leucomycin at 90 and 180ppm for the prevention of porcine proliferative enteropathy (PPE) in experimentally infected pigs. A total of 90 commercial five-week-old pigs were randomly assigned to receive leucomycin in feeding at 90 (T2), 180ppm (T3), or untreated (T1). All animals in the treated groups received medicated feed for 14 days starting one day before inoculation. Each pig was inoculated intragastrically with approximately 4.5x10(9) Lawsonia intracellularis in the form of porcine intestinal mucosal homogenate. Body weight, feed consumption and clinic signs were evaluated throughout the study. Necropsies and gross evaluation of intestines were performed in all animals on day 23 post-inoculation (pi) or at death, and ileum samples were collected for immunohistochemistry (IHC) for L. intracellularis. Clinical presentation of the disease was more evident in the non-medicated group (T1) than in the medicated ones (T2, T3) between days 16 and 21pi. Average daily gain, average daily feed consumption and feed conversion efficiency were better in groups treated with either dose of leucomycin. The total intestine lesion length per group (T1, T2 and T3) was 869, 473 and 331cm, respectively. The majority of the animals (84.4%) were positive for L. intracellularis antigen in ileum sections stained by IHC. Under the conditions of this study, leucomycin administered in feed at 90 and 180ppm for 14 days was effective in improving performance of pigs inoculated with intestinal homogenate containing L. intracellularis.

Development and validation of a rapid multi-class method for the confirmation of fourteen prohibited medicinal additives in pig and poultry compound feed by liquid chromatography–tandem mass spectrometry

A confirmatory method has been developed to allow for the analysis of fourteen prohibited medicinal additives in pig and poultry compound feed. These compounds are prohibited for use as feed additives although some are still authorised for use in medicated feed. Feed samples are extracted by acetonitrile with addition of sodium sulfate. The extracts undergo a hexane wash to aid with sample purification. The extracts are then evaporated to dryness and reconstituted in initial mobile phase. The samples undergo an ultracentrifugation step prior to injection onto the LC–MS/MS system and are analysed in a run time of 26 min. The LC–MS/MS system is run in MRM mode with both positive and negative electrospray ionisation. The method was validated over three days and is capable of quantitatively analysing for metronidazole, dimetridazole, ronidazole, ipronidazole, chloramphenicol, sulfamethazine, dinitolimide, ethopabate, carbadox and clopidol. The method is also capable of qualitatively analysing for sulfadiazine, tylosin, virginiamycin and avilamycin. A level of 100 μg kg −1 was used for validation purposes and the method is capable of analysing to this level for all the compounds. Validation criteria of trueness, precision, repeatability and reproducibility along with measurement uncertainty are calculated for all analytes.

Evaluation of two liquid chromatography/tandem mass spectrometry platforms for quantification of monensin in animal feed and milk

Monensin is an anticoccidial drug that has been used as an additive in medicated feed. The United States Food and Drug Administration (USFDA) has included monensin in the national surveillance schemes for residues in foodstuff. In this study, two simple, selective and rapid methods were developed to determine monensin content in animal feed and milk. The methods enabled the detection of monensin residues as low as 1 ppb. Moreover, the two methods were used as models to compare two common liquid chromatography/tandem mass spectrometry (LC/MS/MS) platforms; an LC linear ion trap (LC/LIT) and an LC triple quadrupole (LC/QqQ). The two instrument platforms were evaluated for their matrix effect dependence, precision and accuracy. The LC/QqQ presented a lower limit of detection and limit of quantitation (LOD and LOQ) and showed less matrix dependence as compared to the LC/LIT. The LC/QqQ instrument also demonstrated a better intermediate precision. For example, the intermediate precision standard deviation calculated for 27 analyses across three days was 4% and 11% for LC/QqQ and LC/LIT, respectively. Overall, the LC/QqQ represents a better choice for analysis of monensin with respect to LOD, LOQ, matrix interference and precision.

Depletion of florfenicol amine, marker residue of florfenicol, from the edible fillet of tilapia ( Oreochromis niloticus x O. niloticus and O. niloticus x O. aureus) following florfenicol administration in feed

Aquaflor ®, a 50% feed premix containing the broad spectrum antibacterial agent florfenicol is available globally to control mortality associated with economically significant systemic bacterial diseases of fish. Florfenicol (FFC) is effective in controlling mortality associated with Streptococcus iniae in tilapia Oreochromis sp. when administered in medicated feed at a dose of 15 mg/kg bodyweight (BW)/d for 10 consecutive days. Our objective was to characterize the depletion of the FFC marker residue, florfenicol amine (FFA), from the edible tissue of market-weight Nile tilapia O. niloticus x O. niloticus and hybrid tilapia O. niloticus x O. aureus offered feed medicated with FFC at a nominal dose rate of 15 mg/kg BW/d for 12 days. Near market-weight tilapia were obtained from a commercial tilapia farm, distributed to 2 single pass (one for Nile tilapia and one for hybrid tilapia), flow-through systems and maintained at 27 °C under a 15 h light:9 h dark photoperiod over a 41-d pre-dosing period. During the dosing period, tilapia were offered feed medicated with FFC at a concentration of 1.479 g/kg at 1% BW daily divided in three equal offerings. The initial 10-d dosing period was extended to 12 d because one tank did not consume > 75% of the feed offered during the first two dosing days. The total dose consumed by fish in each of the 2 tanks ranged from 147 to 167 mg/kg. Once during the pre-dose period and on days 1, 2, 4, 7, 14, 21, and 28 of the post-dose period, groups of fish were indiscriminately removed from each tank, measured for weight and length, scaled, filleted, and the skin-on fillets stored at <−70 °C. Frozen fillets were individually homogenized, extracted, and FFA concentration was determined by high-performance liquid chromatography with UV detection. Florfenicol amine is rapidly eliminated from tilapia fillet after withdrawal from medication and depletion followed first-order kinetics with an estimated half-life of 2.32 d. The FFA tolerance limit, calculated as the 99th percentile of the potential residue level at 95% confidence, had depleted to less than the 1 µg/g maximum residue level by 6.14 d after the dosing period.