[Objective] The aims of the present study were to assess the biological characteristics of Lactobacillus plantarum derived from Yichun forest pig and to comprehensively evaluate its application potential in the development of probiotic preparations. [Method] A lactic acid bacterial strain （P1M1） isolated from the feces of the healthy forest pig in Yichun City, Heilongjiang Province, was biochemically identified and then molecularly confirmed by using 16S rDNA PCR amplification and sequencing technology. The curves of growth and acid production of the strain were drawn, and its tolerance to acid （pH values at 2.0, 3.0 and 4.0） and bile salt （concentrations at 0.15% and 0.30%） were evaluated. The sensitivity of the strain to 13 antimicrobial agents and its inhibitory effect on Staphylococcus aureus （S. aureus） of porcine origin were examined. Tests were also conducted to assess the free radical scavenging ability, exopolysaccharides yield and safety to mice of the strain. [Result] Based on the biochemical and molecular identification results, P1M1 strain was identified as Lactobacillus plantarum （L. plantarum）. L. Plantarum P1M1 strain had glycolytic ability. Its logarithmic growth phase was 2-10 h of cultivation. After 18 h of cultivation, the pH value of its culture medium stabilized at 3.8-3.9. Its 3 h survival rates at pH values of 2.0, 3.0 and 4.0 were （48.97±0.61）%, （64.19±0.94）% and （78.44 ± 1.36）%, respectively, and those at bile salt concentrations of 0.15% and 0.30% were （53.86±1.14）% and （32.87±0.75）%, respectively. It was sensitive to erythromycin, enrofloxacin, norfloxacin, tobramycin, ampicillin, amoxicillin, cefoperazone, cefradine and ceftazidime, and had pronounced inhibitory effect on S. aureus of porcine origin. The scavenging rates of its cell-free supernatant against DPPH free radical, hydroxyl radical and ABTS free radical were （91.65±1.44）%, （87.32±0.22）% and （89.79±0.59）%, respectively, all significantly （P<0.05） higher than those of its intact cell suspension. Its exopolysaccharides yield was （796.73±2.43） mg/L. No death or organ damage was observed after continuous gavages of the L. plantarum P1M1 strain to mice for 2 weeks. [Conclusion] Forest pig derived L. plantarum P1M1 strain shows an early entrance into the logarithmic growth phase, has glycolytic characteristics, strong acid producing ability, and tolerance to acid and bile salt. It is sensitive to various antimicrobial agents and capable of inhibiting the growth of S. aureus of porcine origin. Furthermore, it has strong antioxidant capacity and high exopolysaccharides yield, and is safe for mice. Accordingly, it can be used as a candidate strain for the development of probiotic preparations.

[Objective] The aims of the present study were to establish an ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry （UHPLC-MS/MS） method for simultaneous detection of 64 drugs in compound feed, and to improve the detection efficiency of illegal additives. [Method] Waters HSS T3 column （2.1 mm×100 mm, 1.8 μm） was used for separation. Gradient elution was performed using 0.1% formic acid aqueous solution as mobile phase A and acetonitrile containing 0.1% formic acid as mobile phase B, respectively, with a flow rate of 0.40 mL/min and sample size of 2 μL. Positive-ion electrospray ionization （ESI） source scanning mode was used for detection, and multiple reaction monitoring （MRM） mode was used for signal acquisition. The recovery rates of the target drugs obtained with 4 kinds of sample extraction solvents and 2 types of solid-phase extraction column were compared to determine the optimal method of sample pretreatment. Detection of the 64 drugs in 100 batches of compound feed samples of different sources collected in Ningxia Hui Autonomous Region was carried out with the established UHPLC-MS/MS method. [Result] The compound feed samples were extracted with acetonitrile aqueous solution （acetonitrile∶water=8∶2, V/V） containing 0.2% formic acid after homogenization. Oasis PRiME HLB solid-phase extraction column was used to purify the samples. The recovery rates of most target drugs was above 60%. In the concentration range of 5.0-200.0 μg/L, a good linear relationship of the 64 drugs was observed, and their correlation coefficients （R） were all greater than 0.99. The limit of quantitation of different drugs was 5.0-10.0 μg/kg. The average recovery rates of 3 spiking levels at 5.0, 20.0 and 50.0 μg/kg ranged from 41.00% to 120.49%. The intra- and inter-assay relative standard deviations （RSDs） were 0.54%-15.94% and 1.25%-13.64%, respectively. No target drug was detected in the 100 batches of compound feed samples. [Conclusion] The established UHPLC-MS/MS method has good linear relationship, high recovery rate, good precision, high reproducibility and good operability, and can be used for screening the 64 drugs illegally added in compound feed.

The use of biological feed as an antibiotic alternative has gained a lot of attention in light of the antibiotic ban in animal feed. Biological feed offers benefits including improving feed quality, enhancing animal production performance, boosting animal immunity and regulating animal gut microbiota, exhibiting an increasing market acceptance. This paper introduced the definition and classification of biological feed, summarized the research progress on the application of biological feed in cattle, sheep and pig production taking fermented feed and bacterium and enzyme synergistic fermented feed as examples, analyzed the problems in the current application of biological feed, and put forward relevant suggestions, in hoping to provide references for the development and application of biological feed.