Intrauterine oxygen/ozone mixture for the treatment of subclinical endometritis in repeat breeder cows

Repeat Breeder Syndrome is a multifactorial condition in which subclinical endometritis (SCE) may represent an underlying cause. The aim of this study was to evaluate the efficacy of an intrauterine oxygen/ozone gas mixture administered at heat in Repeat Breeder (RB) cows with SCE. Of 156 RB cows, 57 affected with SCE based on cytological evaluation using the cytobrush technique were enrolled in the controlled clinical trial. These cows were randomly allocated, using randomization software, into two groups including treated (GM; 30) and untreated (CON; 27) animals. The intrauterine bacteria occurrence was monitored before (T0) and 12 h (T12) after treatment, along with an evaluation of reproductive parameters after the 1st and 2nd artificial insemination (AI). At T0, both groups showed similar bacterial positivity rates (12/30, 40% GM vs. 14/27, 51.85% CON; p = 0.43). At T12, all GM-positive cows had cleared cultivable bacteria, whereas all CON-positive cows remained bacteriological positive (p = 0.00001). This result indicated a 100% in-vivo clearance of cultivable bacteria. Furthermore, increasing pregnancy percentages were recorded after the 1st and 2nd AI in GM group (9/30, 30% and 9/21, 43%, respectively; p < 0.05) compared to the CON group (2/27, 7% and 1/25, 4%, respectively; p < 0.001). Overall, these preliminary findings suggest that intrauterine ozone therapy may represent a promising complementary tool for the management of SCE in RB cows, although further studies are required to confirm its efficacy and long-term benefits.