Chronically infected mares do not respond to traditional therapy for endometritis; thus, alternative-therapeutic modalities have been incorporated into clinical practice primarily to treat these infections; unfortunately, some of the therapeutics have no documented efficacy. The study aimed to assess the in vitro antimicrobial activity of some alternative-therapies currently used in practice to treat chronic endometritis. Therapies tested were Botu-killer® (Botupharma), Coke®, Dimethyl-sulfoxide 40% (DMSO), Hydrogen-Peroxide 10% (H2O2), Ozonated-Ringer (O3; 60μg/mL of ozone for 10 min), povidone-iodine 4% (PVPI) and platelet-rich plasma (PRP; 1056±198 × 103 platelets/μL, activated with CaCl10%). Microorganisms causing chronic endometritis Escherichia coli (E.coli), Pseudomonas aeruginosa (Pseudo), Klebsiella pneumoniae (Kleb), Staphylococcus aureus (Staph), and Candida albicans (Candida) were identified with MALDI-TOF/MS and confirmed with 16s-rDNA sequencing. The percentage of inhibition (PI) was determined using a microdilution Mueller-Hinton broth (MH) method in 96-well plates as defined by the Clinical-Laboratory-Standards-Institute (2019). The first-three lanes were used as negative controls (NTT and MH), and the last row as the positive control (MH and microorganisms). Thests were performed in triplicate, using three lanes for each microorganism. The optical density of each well was measured at 570 nm using a Spectramax M2 spectrophotometer (Molecular Devices, USA). PI was calculated by the difference between the mean of the triplicates against positiveand negative controls. The minimal inhibitory concentrations (MIC) of 50% and 90% of each microorganism were determined using a non-linear regression dose-response stimulation mode considering the PI and concentration of each NTT. The MIC 100% was determined by the resazurin-dye technique. The concentrations of each NTT were transformed in log(X) to normalize data. PRP concentration was based on platelet concentration (x103/μL), while the other NTTs were based on each dilution (%). The MIC-50% and -90% of each NTT were, respectively: BK (Staph 7.2, 8.5; E.coli 15.4, 19.4; Pseudo 7.3, 10.6; Kleb 0.8, 6.5; Candida 0.6, 2.6); Coke (E.coli 50.7, 54.1); DMSO (Staph 20.4, 21.7; E.coli 19.7, 21.0; Pseudo 13.7, 18.2; Kleb 15.7, 25.4; Candida 16.7, 25.3); H2O2 (Staph 0.08, 0.06; E.coli 0.23, 0.32; Pseudo 0.6, 0.7; Kleb 0.08, 0.12; Candida 10.2, 5.004); O3 (Kleb 76.25, 273.5); PVPI (Pseudo 0.6, 0.63) and PRP (Staph (336±130; 814± 406), E.coli (93±16; 156±52), Kleb (540±315; 1349±836) and Candida (556±160). The only NTTs that were able to show a MIC 100 were: BK (Staph-25; E.coli-12.5; Pseudo-50; Kleb-25; Candida-25); H2O2 (Staph-0.19; E.coli-1.25; Pseudo-1.25; Kleb-0.38; Candida-0.38); PRP (Staph 528±99 (16%); E.coli 528±99 (72%), 264±50 (28%); Pseudo 528±99 (33%). In conclusion, BK and H2O2 showed the greatest in vitro antimicrobial activity against all microorganisms tested. In contrast, PRP showed selective efficacy against some microorganisms. The remaining products tested showed no significant antimicrobial activity.