| Tylosin is a macrolide antibiotic for livestock and poultry produced by Streptomyces fradiae.It has a broad spectrum of antibacterial activity and is widely used in the prevention and treatment of animal diseases and as animal growth promoter.However,the large-scale use of tylosin in animal husbandry has caused problems such as drug residues in animal-derived food,bacterial resistance,environmental pollution,etc.At present,the research on tylosin mainly focuses on the analysis of animal-derived food,livestock manure and other samples.There are few studies on the detection of tylosin in feed.Therefore,it is of great significance to establish a method for detecting tylosin in feeds with simplicility,accuracy and reliability.In this research,we established an analytical method for the determination of tylosin in feed with high performance liquid chromatography-ultraviolet detector.The separation conditions of liquid chromatography were optimized to obtain the highest response value and the best resolution of the analyte.Dispersive solid-phase extraction was used to pretreat five representative feed samples(including poultry full-price feed,poultry premix feed,medium pig full-price feed,large pig premix feed and big pig full-price feed).The sample was alkalized by sodium borate buffer(p H= 10.0)and extracted with ethyl acetate.The extract was evaporated to dryness under a steam of nitrogen,dissolved in 1m L mobile phase,purified by BRP adsorbent,then the supernatant was filtered and used for analysis.Acetonitrile and 0.02 mol/L potassium dihydrogen phosphate(p H=2.5)were used as mobile phase,with a ratio of 32∶68.The analyte was separated by an Agilent Poroshell120 EC-C8 column(250 mm × 4.6 mm id,4 μm)and then isocratic eluted by mobile phase noted above.The results showed that tylosin had a good linearity in the concentration range of 1.0 to 200 μg/m L,and the correlation coefficient(r)was 0.9996.Three concentrations of tylosin were added to the five feed samples,and the average recovery rate of tylosin was between 72.4% and 96.6%.The intra-assay precision was below 12.2% and the inter-assay precision was less than 10.7%.This developed method is fast,accurate and reliable.Therefore,it’s suitable for routine testing and monitoring of tylosin in feed and feed additives.Based on the established method noted above,we further explored whether the black soldier fly could accelerate the degradation of tylosin.The feed,which was mixed with the black soldier fly and spiked with tylosin phosphate,was as the test group,the feed spiked with tylosin phosphate was as the positive group.The feed and black soldier fly were collected on day1,6,11 and 21 of the experiment,respectively.The established method was used to detect the collected samples.The results showed that the degradation rate of tylosin in the test group was higher than that in the untreated group at all the time points,indicating the black soldier fly could accelerate the degradation of tylosin.We also evaluated that the relationship of the amount of Black soldier fly with the degradation of tylosin.Thus,three groups of 300 g,600 g and 900 g black soldier fly were inoculated into 4 kg feed with tylosin tartrate.Our results showed that in a certain extent,with the increase of the amount of black soldier fly,the degradation of tylosin was quicker.That’s to say,the black soldier fly can accelerate the degradation of tylosin.Our studies provide theory evidence for the degradation of tylosin in livestock manure and waste dregs. |
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