Tylosin Concentration Research Articles

Bioconversion of cow manure through vermicomposting: effects of tylosin concentration on the weight of worms and manure quality

This study investigated batch-fed vermicomposting of cow manure, with a specific focus on assessing the effects of tylosin on the weight of earthworms and the overall quality of the resulting manure. Five reactors, including three concentrations of tylosin (50, 100, and 150 mg/kg) and two control reactors, were employed. Residual tylosin concentrations were measured using high-performance liquid chromatography (HPLC). Quality parameters such as pH, temperature, volatile solids (VS), organic carbon content (OCC), electrical conductivity (EC), ash content, C/N ratio, total Kjeldahl nitrogen (TKN), and microbial content were evaluated. The toxicity and maturity of vermicompost were assessed by determining the germination index (GI). The study also monitored variations in the earthworm’s weight. The results demonstrated a decreasing trend in VS, OCC, C/N, and fecal coliforms, along with increased pH, EC, ash content, and TKN during the vermicomposting process. Furthermore, investigations revealed significant reductions in the reactors with tylosin concentrations of 50, 100, and 150 mg/kg, resulting in the removal of 98%, 90.48%, and 89.38% of the initial tylosin, respectively. This result confirms the faster removal of tylosin in reactors with lower concentrations. Degradation of tylosin also conforms to first-order kinetics. The findings showed a significant influence of tylosin on the weight of Eisenia fetida earthworms and the lowest antibiotic concentration led to the highest weight gain. Finally, the high percentage of germination index (90–100%) showed that the quality and maturity of vermicompost is by national and international standards.

Effect of continuous in-feed administration of tylosin to feedlot cattle on macrolide and tetracycline resistant enterococci in a randomized field trial

Liver abscess causes substantial economic loss to the beef cattle industry through liver condemnation, reduced animal performance, and carcass yield. Continuous in-feed use of tylosin is the most effective and a commonly used practice in beef cattle production to prevent liver abscess. However, such mass medication can increase the level of antimicrobial resistant bacteria. We investigated the effect of continuous in-feed use of tylosin in feedlot cattle on (i) concentrations and prevalence of erythromycin-resistant (ERYr) and tetracycline-resistant (TETr) enterococci; (ii) associated antimicrobial resistance genes (ARGs) for resistance; (iii) species distribution; iv) macrolide and tetracycline resistance gene concentrations; and (v) tylosin concentration. A cohort of weaned calves were randomized to receive tylosin-medicated feed (Tylosin; n = 10) or nonmedicated feed (Control; n = 10) for a full feedlot cycle. Feces, feed and pen-surface samples were collected and processed by culture, droplet digital PCR, and liquid chromatography/mass spectroscopy for bacterial enumeration, detection and characterization, ARG quantification, and tylosin concentration, respectively. Data were analyzed by mixed effects linear- or binary-regression models depending on the outcomes. Tylosin administration significantly increased fecal concentration (P < 0.001) and prevalence (P = 0.021) of ERYr enterococci and erm(B) gene concentration (P < 0.001), compared to the control group. Interestingly, tylosin administration significantly reduced (P = 0.037) fecal TETr enterococci concentration compared to the control group, with no significant effect (P = 0.758) on fecal tet(M) concentration. In both treatment groups, enterococci concentrations increased over time, peaking on 174 days in feed before returning to the baseline. ERYr enterococci concentration was significantly (P = 0.012) higher in tylosin medicated feeds, with no significant effect (P = 0.321) on TETr enterococci concentration. Pen-surface concentration of ermB was significantly (P = 0.024) higher in the tylosin group, with no significant effect (P > 0.05) on bacterial concentrations. Increased diversity and a shift in the composition of enterococcal species and ARGs were observed over time, although tylosin use did not significantly affect (P > 0.05) their prevalence. Tylosin concentration was significantly higher in the feces of tylosin administered cattle (P < 0.001) and medicated feed (P = 0.027), with numerically higher pen-surface concentration (P = 0.065) in the tylosin group. In conclusion, continuous in-feed use of tylosin in feedlot cattle increases macrolide resistant enterococci and its fecal excretion, while decreasing tetracycline resistance. Two medically important species, E. faecium and E. faecalis, were predominant regardless of resistance status or sample source. Risk-based approaches including label changes to limit tylosin use such as withdrawal period, and development of effective manure treatments are potential areas of research to reduce environmental and public health impacts.

Hydrothermal pre-treatment followed by anaerobic digestion for the removal of tylosin and antibiotic resistance agents from poultry litter.

Hydrothermal pretreatment (HPT) followed by anaerobic digestion (AD) is an alternative for harvesting energy and removing organic contaminants from sewage sludge and animal manure. This study investigated the use, in an energetically sustainable way, of HPT and AD, alone or combined, to produce methane and remove tylosin and antimicrobial resistance genes (ARG) from poultry litter (PL). The results showed that HPT at 80°C (HPT80), followed by single-stage AD (AD-1S), led to the production of 517.9 ± 4.7 NL CH4 kg VS-1, resulting in 0.11 kWh kg PL-1 of electrical energy and 0.75MJkg PL-1 of thermal energy, thus supplying 33.6% of the energy spent on burning firewood at a typical farm. In this best-case scenario, the use of HPT alone reduced tylosin concentration from PL by 23.6%, while the process involving HPT followed by AD-1S led to the removal of 91.6% of such antibiotic. The combined process (HPT80 + AD-1S), in addition to contributing to reduce the absolute and relative abundances of ARG ermB (2.13 logs), intI1 (0.39 logs), sul1 (0.63 logs), and tetA (0.74 logs), led to a significant removal in the relative abundance of tylosin-resistant bacteria present in the poultry litter.

Tylosin in anaerobic reactors: degradation kinetics, effects on methane production and on the microbial community.

Tylosin eliminated in animal waste, during therapeutic treatment, can be efficiently removed in anaerobic systems. The present study investigated the influence of tylosin concentration and assessed its degradation kinetics and the microorganisms involved in each stage of its anaerobic digestion (hydrolysis/acidogenesis; acetogenesis; methanogenesis). The results showed a stimulating effect on methane production with increasing tylosin concentration in the poultry litter up to 80mg kg-1 tylosin (232.9 NL CH4kg SV-1). As for tylosin degradation, greater removal of antibiotics was observed in the methanogenic phase (88%), followed by acetogenic (84%) and hydrolytic/acidogenic (76%) phases. The higher rate of tylosin degradation obtained in the methanogenic step, is mainly related to the co-metabolic effect exerted by the presence of acetate and its degradation by acetoclastic methanogens. Indeed, metagenomic analyses suggested a syntrophic action between archaea of ​​the genus Methanobacterium, and bacteria such as Clostridium and Flexilinea, which seemed decisive for tylosin degradation.

Infrared spectroscopy combined with random forest to determine tylosin residues in powdered milk

The contamination of milk by antibiotic residues is a worldwide health and food safety problem. There is a need to develop new methods for the rapid determination of antibiotic residues in milk. A method has been developed for determining tylosin residues directly in powdered milk using Fourier Transformed Infrared spectroscopy (FTIR). Tylosin is a broad-spectrum macrolide antibiotic. The spectra obtained were submitted to chemometric analysis to obtain a prediction model for tylosin concentration in powdered milk. Using the Boruta algorithm, the absorption bands related to the milk contamination by the antibiotic were identified. Random forest was shown to be adequate for the prediction of tylosin residues in milk at low concentrations (≤ 100 μg L-1) and the prediction model generated showed high correlation and determination coefficients (greater than 0.95). The proposed methodology proved to be efficient for the investigation of antibiotic residues in powdered milk.

A study towards minimising tylosin concentration and antibiotic resistance genes in tylosin fermentation dreg fertilizer

This study proposed a comprehensive treatment plan consisting of “high temperature + oxidant pre-treatment” before compost and “thermal treatment” after compost to realise the compost resource utilisation of tylosin fermentation dreg. The study revealed that the tylosin concentration in the dregs was reduced by 97.1% under the optimal pre-treatment conditions. Subsequently, high-temperature compost was performed by adding compost auxiliary materials and the content of tylosin in the compost material was below the detection limit (<1 mg/kg) after 15 days. During the whole aerobic fermentation process, 70.8% of tylosin removal in the compost material was contributed by microbial metabolism, 23.0% was caused by high-temperature destruction of the compost, and 5.4% was due to the natural decomposition of tylosin. Finally, the finished compost product was further thermal-treated at 130 °C for 2 h, which could destroy the antibiotic resistance genes and maintain the seed germination index of the obtained fertiliser >80%, indicating the low plant toxicity of the compost. Based on this information, the tylosin fermentation dreg composting comprehensive treatment scheme proposed in this study is a safe, efficient and feasible resource utilisation scheme for tylosin fermentation dreg.

Pharmacokinetics, tissue residues, and ex vivo pharmacodynamics of tylosin against Mycoplasma anatis in ducks.

The pharmacokinetics of tylosin were investigated in 3 groups of ducks (n=6). They received a single dose of tylosin (50mg/kg) by intravenous (IV), intramuscular (IM), and oral administrations, respectively. Plasma samples were collected at various time points to 24hr post-administration to evaluate tylosin concentration over time. Additionally, tylosin residues in tissues and its withdrawal time were assessed using 30 ducks which received tylosin orally (50mg/kg) once daily for 5 consecutive days. After IV administration, the volume of distribution, elimination half-life, area under the plasma concentration-time curve, and the total body clearance were 7.07±1.98L/kg, 2.04hr, 19.47µg hr/ml, and 2.82 Lhr-1 kg-1 , respectively. After IM and oral administrations, the maximum plasma concentrations were 3.70 and 2.75µg/ml achieved at 1 and 2hr, and the bioavailability was 93.95% and 75.77%, respectively. The calculated withdrawal periods of tylosin were 13, 8, and 5days for kidney, liver, and muscle, respectively. For the pharmacodynamic profile, the minimum inhibitory concentration for tylosin against M. anatis strain 1,340 was 1µg/ml. The calculated optimal oral dose of tylosin against M. anatis in ducks based on the ex vivo pharmacokinetic/pharmacodynamic modeling was 61mgkg-1 day-1 .

Dissipation of Antimicrobials in a Seasonally Frozen Soil after Beef Cattle Manure Application.

Land application of manure containing antimicrobials results in the dispersion of the antimicrobials in agro-ecosystems. Dissipation of excreted antimicrobials in seasonally frozen agricultural soils has not been fully characterized under field conditions. This study investigated the field dissipation kinetics of chlortetracycline, sulfamethazine, and tylosin over a 10-mo period after fall application of manure from cattle () administered 44 mg chlortetracycline (chlortetracycline treatment [CTC]), 44 mg each of chlortetracycline and sulfamethazine (CTCSMZ), or 11 mg tylosin per kg feed daily. Antimicrobial concentrations in manured soil reflected the same relative concentrations in manure: chlortetracycline > sulfamethazine > tylosin. The first-order dissipation half-life (DT) for chlortetracycline from the CTCSMZ treatment was 77 d during the growing season and 648 d during the nongrowing season when the soil was frozen for an extended period. By comparison, dissipation of chlortetracycline added alone (treatment CTC) did not differ significantly between the two seasons (mean DT, 121 d). During the nongrowing season, chlortetracycline from CTC dissipated faster ( = 0.004) than that from the CTCSMZ treatment, indicating that the presence of sulfamethazine may have altered the dissipation of chlortetracycline. Dissipation kinetics for sulfamethazine and tylosin were not determined due to low detection in the manure-amended soil. Sulfamethazine was detected (up to 16 ± 10 µg kg) throughout the 10-mo monitoring period. Tylosin concentration was ≤11 ± 6.6 µg kg and gradually dissipated. Chlortetracycline was detectable 10 mo after application in the seasonally frozen soil, indicating a risk for residue build-up in the soil and subsequent offsite contamination.

Runoff losses of excreted chlortetracycline, sulfamethazine, and tylosin from surface-applied and soil-incorporated beef cattle feedlot manure.

Veterinary antimicrobials in land-applied manure can move to surface waters via rain or snowmelt runoff, thus increasing their dispersion in agro-environments. This study quantified losses of excreted chlortetracycline, sulfamethazine, and tylosin in simulated rain runoff from surface-applied and soil-incorporated beef cattle ( L.) feedlot manure (60 Mg ha, wet wt.). Antimicrobial concentrations in runoff generally reflected the corresponding concentrations in the manure. Soil incorporation of manure reduced the concentrations of chlortetracycline (from 75 to 12 μg L for a 1:1 mixture of chlortetracycline and sulfamethazine and from 43 to 17 μg L for chlortetracycline alone) and sulfamethazine (from 3.9 to 2.6 μg L) in runoff compared with surface application. However, there was no significant effect of manure application method on tylosin concentration (range, 0.02-0.06 μg L) in runoff. Mass losses, as a percent of the amount applied, for chlortetracycline and sulfamethazine appeared to be independent of their respective soil sorption coefficients. Mass losses of chlortetracycline were significantly reduced with soil incorporation of manure (from 6.5 to 1.7% when applied with sulfamethazine and from 6.5 to 3.5% when applied alone). Mass losses of sulfamethazine (4.8%) and tylosin (0.24%) in runoff were not affected by manure incorporation. Although our results confirm that cattle-excreted veterinary antimicrobials can be removed via surface runoff after field application, the magnitudes of chlortetracycline and sulfamethazine losses were reduced by soil incorporation of manure immediately after application.

Occurrence of tylosin in swine wastewater in Mexico

This study determined a tylosin concentration in swine wastewater located in a Mexican pig farm, during different stages of the pigs' growth. The detection of antibiotics in swine wastewater is complex due to its high concentration of solids. Analytical method was developed for detection of tylosin in swine wastewater and swine slurry. Average recoveries of tylosin in the liquid and solid phase were greater than 51 and 44%, respectively, with a greater total recovery of 95%. The results indicated the presence of tylosin in swine wastewater and slurry at concentrations greater than the ones reported in the literature. In grab samples of swine wastewater, the tylosin detected showed concentrations of 56, 72 and 8.6 μg L(-1), in breeding-gestation, nursery pigs, and grow-finishing area, respectively. In composite samples, the concentration of tylosin was 11.8 μg L(-1) for the breeding-gestation area and 2.4 μg L(-1) for the grow-finishing area. For slurry, the concentration of tylosin was 20.6 and 17.8 μg L(-1), for the breeding-gestation and grow-finishing area, respectively. This study presents the detection of a high concentration of tylosin in breeding-gestation and nursery pigs. Traces of tylosin in wastewater from grow-finishing stage were found although the animals were not receiving antibiotics.

Effect of Biochar Amendment on Tylosin Adsorption-Desorption and Transport in Two Different Soils

The role of biochar as a soil amendment on the adsorption-desorption and transport of tylosin, a macrolide class of veterinary antibiotic, is little known. In this study, batch and column experiments were conducted to investigate the adsorption kinetics and transport of tylosin in forest and agricultural corn field soils amended with hardwood and softwood biochars. Tylosin adsorption was rapid at initial stages, followed by slow and continued adsorption. Amounts of adsorption increased as the biochar amendment rate increased from 1 to 10%. For soils with the hardwood biochar, tylosin adsorption was 10 to 18% higher than that when using the softwood biochar. Adsorption kinetics was well described by Elovich equation ( ≥ 0.921). As the percent of biochar was increased, the rates of initial reactions were generally increased, as indicated by increasing α value at low initial tylosin concentration, whereas the rates during extended reaction times were generally increased, as indicated by decreasing β value at high initial tylosin concentration. A considerably higher amount of tylosin remained after desorption in the corn field soil than in the forest soil regardless of the rate of biochar amendment, which was attributed to the high pH and silt content of the former. The breakthrough curves of tylosin showed that the two soils with biochar amendment had much greater retardation than those of soils without biochar. The CXTFIT model for the miscible displacement column study described well the peak arrival time as well as the maximum concentration of tylosin breakthrough curves but showed some underestimation at advanced stages of tylosin leaching, especially in the corn field soil. Overall, the results indicate that biochar amendments enhance the retention and reduce the transport of tylosin in soils.

Effects of the antimicrobial tylosin on the microbial community structure of an anaerobic sequencing batch reactor

The effects of the antimicrobial tylosin on a methanogenic microbial community were studied in a glucose-fed laboratory-scale anaerobic sequencing batch reactor (ASBR) exposed to stepwise increases of tylosin (0, 1.67, and 167 mg/L). The microbial community structure was determined using quantitative fluorescence in situ hybridization (FISH) and phylogenetic analyses of bacterial 16S ribosomal RNA (rRNA) gene clone libraries of biomass samples. During the periods without tylosin addition and with an influent tylosin concentration of 1.67 mg/L, 16S rRNA gene sequences related to Syntrophobacter were detected and the relative abundance of Methanosaeta species was high. During the highest tylosin dose of 167 mg/L, 16S rRNA gene sequences related to Syntrophobacter species were not detected and the relative abundance of Methanosaeta decreased considerably. Throughout the experimental period, Propionibacteriaceae and high GC Gram-positive bacteria were present, based on 16S rRNA gene sequences and FISH analyses, respectively. The accumulation of propionate and subsequent reactor failure after long-term exposure to tylosin are attributed to the direct inhibition of propionate-oxidizing syntrophic bacteria closely related to Syntrophobacter and the indirect inhibition of Methanosaeta by high propionate concentrations and low pH.

Improvement of tylosin production from Streptomyces fradiae culture by decreasing the apparent viscosity in an air-lift bioreactor

Tylosin production in the culture of Streptomyces fradiae T1558 was improved by decreasing the apparent viscosity by means of a newly designed medium. When a medium containing 15 g/ l Pharmamedia (a proprietary nutrient derived from cotton seed) and 25 g/ l gluten meal was used in a 3- l air-lift bioreactor, the tylosin concentration and apparent viscosity of the broth were 2.1 g/ l and 190 cP, on day 10 with preferential filamentous growth, while the DO level could hardly be controlled at an appropriate level during fermentation because of the high apparent viscosity. However, when a newly designed medium containing 10 g/ l Pharmamedia and 10 g/ l gluten meal was used, the tylosin production and apparent viscosity of the broth were 7.4 g/ l and 50 cP, on day 10 with preferential pellet growth and appropriate control of DO level. The decrease in the apparent viscosity which was dependent on morphological change, was effective in increasing the tylosin productivity in an air-lift bioreactor through the improvement of mass transfer.

Efficient tylosin production from Streptomyces fradiae using rapeseed oil

Tylosin production in flask and jar fermentor culture of Streptomyces fradiae using seven different vegetable oils as sole carbon sources was investigated. Among the vegetable oils, rapeseed oil was the best carbon source for tylosin production. When the initial rapeseed oil concentration was 60 g/ l, the maximum tylosin concentration reached was 7.0 g/ l, which was about 1.6- and 7-fold that reached using starch and glucose, respectively, at the same initial concentration. Although oil consumption increased with increasing agitation rate, the highest tylosin yield was obtained using an agitation rate of 400 rpm. This indicates that in the case of using an insoluble carbon source, use of an appropriate agitation rate is important for efficient production of tylosin.

Particle Concentration Fluorescence Immunoassay for Determination of Tylosin in Premix, Feeds, and Liquid Feed Supplement: Comparison with Tiirbidimetric Assay

Abstract A rapid, competitive particle concentration fluorescence immunoassay (PCFIA) for the determination of tylosin (Tylan) concentrations in extracts of pre-mix, feeds (cattle, chicken, and swine), and liquid feed supplement is described. Tylosin-β-phyco-erythrin conjugate, tylosin standard or diluted sample extracts, and rabbit anti-tylosin antibody are incubated for 15 min in PCFIA plates. Rabbit anti-tylosin antibody is then captured, during a 15 min incubation, with goat anti-rabbit antibody that is attached to latex beads. Assay plates are washed to remove unbound tylosin-(β-phyco-erythrin and unbound, free tylosin. Fluorescence is measured with a fluorimeter. Tylosin concentration is inversely proportional to the β-phycoerythrin fluorescence signal. The method, evaluated and validated with an IDEXX Screen Machine, shows high specificity with regard to compounds expected to be found in the presence of tylosin, and results correlate well with traditional turbidimetric assay results. Hydrolysis of TUA (tylosin-urea ad-duct), necessary with microbiological methods, and cleanup of extracts beyond filtration are unnecessary with the PCFIA for tylosin.

Disposition of tylosin in goats

The disposition kinetics of tylosin was studied in goats after intravenous (i.v.) or intramuscular (i.m.) injection of 15 mg/kg body wt. Following i.v. injection, tylosin was rapidly and widely distributed with a distribution half-life of 0.2 h and volume of distribution of 1.71/kg. It was slowly eliminated with a mean elimination half-life of 3.04 h and a total body clearance rate of 6.8 ml/kg/min. Following i.m. injection, tylosin was slowly absorbed ( T 1 2 ab of 1.82 h). Tylosin concentration in serum was > 1 μg/ml after 1 h and persisted up to 12 h post-injection. The peak concentration ( C max 2.38 μg/ml) was obtained after 4.19 h. The systemic bioavailability of tylosin injected intramuscularly was 72.6% and the serum protein bound fraction was 37.59% of the total drug. Tylosin was excreted in milk and urine at concentrations much higher than that in serum. Low concentrations of tylosin were reported in ruminal juice of goats. In conclusion tylosin should be injected every 14 h to obtain an appreciable concentration in serum, milk and urine.

Comparison of the Antimycoplasma Activity of Two Commercially Available Tylosin Premixes

Two tylosin premixes (referred to in this report as Premix A1 and tylosin Premix B2), obtained as commercial products from Japan, were analyzed microbiologically for tylosin and by high pressure liquid chromatography (HPLC) for macrolide content. They were evaluated in the feed at concentrations of 550 and 1100 ppm antibiotic activity for the treatment of chickens with induced Mycoplasma gallisepticum (MG) infection. The tylosin microbiological assay value for Premix A was 3.0% below and for Premix B, 7.5% above the tylosin concentration stated on the respective premix labels. Analyses by HPLC showed tylosin Premix A contained 84% tylosin and 16% other macrolide derivatives; whereas, tylosin Premix B contained 42.6% tylosin, 46.6% other macrolides, and 10.8% unidentified material. When the two premixes were administered in the feed for 5 days as treatments for MG-infected chickens, tylosin Premix A was significantly more effective than tylosin Premix B, as measured by reductions in mortality, air sac lesions, and infection as indicated by development of MG antibody. In experiments in pigs where individual macrolide derivatives were used, tylosin was more effective than the other macrolides, desmycosin or macrocin, for the treatment of Mycoplasma hyopneumoniae infection. It is apparent from these studies that commercially available tylosin products may contain varying quantities of tylosin and related macrolide antibiotics and that these differences may significantly affect the efficacy of the products.

High Performance Liquid Chromatographic Analysis of Fermentation Broths: Cephalosporin C and Tylosin

Procedures are described for the analysis of cephalosporin C or tylosin in fermentation broths by high performance liquid chromatography (HPLC). Quantitation of the major components in cephalosporin C broths was done by a system involving separation by an ion-pair technique. Tylosin data were obtained using a reverse phase method. A method of equating uv potency of tylosin to microbiological potency is discussed. A comparison of HPLC with a microbiological method for the determination of tylosin concentration is also made.

Efficacy trials in turkey poults with tylosin tartrate against Mycoplasma gallisepticum and Mycoplasma meleagridis

Tylosin tartrate, administered in the drinking water at a concentration of 0.55 g/litre for the first three days after hatching, was highly effective in controlling the adverse consequences of a Mycoplasma gallisepticum infection, established by air sac injection at one day of age, in turkey poults. Tylosin was ineffective in controlling M meleagridis infections established in embryo or at one day of age when administered in the drinking water of poults. Both mycoplasma isolates used were inhibited in vitro by a tylosin concentration of 0.1 mug/ml.

Studies on the Microbiological Assay of Tylosin in Food

Factors affecting the sensitivity and recovery of tylosin assay for various foods have been studies by the agar diffusion plate method with Sarcina lutea (ATCC 9341) as the test organism. And a modified cylinder-plate or paper disk-plate method was developed based on the experimental results, and brief outline of the technique is as follows:Extraction of tylosin from a food sample is carried out by addition of 4-fold volume of M/15 phosphate buffer of pH 8.0 to the minced sample, and it is homogenized by a blender. The supernatant or filtrate of the homogenate can be used as a test solution for tylosin assay (if necessary, further dilution should be made with the aforementioned extractant).Fifteen peni-cylinders or paper disks are placed in a 15cm diameter plate with a single 17ml seeded layer of modified streptomycin assay agar of pH 8.5. One test solution should be placed in each 3 cylinders or disks on 3 plates. Inhibition zone may be measured after being incubated for 16 to 18 hours at 32°C, and with the average diameter of 9 inhibition zone for one test solution, the tylosin concentration can be calculated in comparison with the standard curve prepared with standard tylosin solution series. Employing this method, the standard curve extends from 0.16 to 2.5ppm (μg/ml) which corresponds to the tylosin contents of about 1 to 16μg/g of sample.The sensitivity of the paper disk-plate method is about 1/4 that of the cylinder-plate technique under the identical condition.