PS1-19. Effects of CIDR-induced Vaginitis and/or Estrus Expression on Ex Vivo Semen Performance When Exposed to Vaginal Fluid.

Abstract

Estrus synchronization protocols using CIDR can induce vaginitis in a substantial proportion of treated females, potentially altering the vaginal environment encountered by sperm at artificial insemination. Our objective was to determine whether vaginal fluid from cows experiencing vaginitis, estrus, both, or neither differentially affects ex vivo sperm performance. Beef cows (n = 25) from Fall 2025 (n = 16) and Spring 2026 (n = 9) received Lutalyse on day -3 and were enrolled in a 7-d CO-Synch protocol, receiving (n = 11) or not receiving (n = 14) a CIDR on day 0. On day 7, CIDRs were withdrawn and scored as 1 = clean without secretion, 2 = clean with clear secretion, 3 = purulent secretion, or 4 = purulent secretion with blood. All CIDR-treated cows scored ≥ 3 and were classified as vaginitis-positive (V+); non-CIDR cows were vaginitis-negative (V−). Also on day 7, cows received an Estrotect patch for estrus detection that was scored on day 10 from 1 to 4 based on percent activation. Cows scoring 3 or 4 (or showing secondary estrus signs when the patch was lost) were classified estrus-positive (E+), and those scoring 1 or 2 were estrus-negative (E−). On day 10, vaginal fluid was collected with a Metricheck device and co-incubated at 37 °C with frozen-thawed semen from a single bull per season, diluted in TRIS-buffered saline. Total motility (TM), progressive motility (PM), and normal morphology were measured by computer-assisted sperm analysis at 0, 1.5, 3, and 6 h of incubation across the two seasons. Data were analyzed by linear mixed-effects models including Vaginitis, Estrus, Hour, and their pairwise interactions, with cow as a random intercept; season was added in combined analyses. In Spring 2026, vaginal fluid from E+ cows maintained greater PM than fluid from E− cows (3.7±0.7% vs. 1.0±0.6%; P = 0.013) during the experimental period. In the combined two-season analysis, V+ vaginal fluid yielded greater PM than V− fluid (5.5±1.5% vs. 2.6±1.4%; P = 0.048). The Vaginitis × Estrus interaction was not significant in any model (P ≥ 0.40), indicating that estrus and vaginitis effects acted approximately additively at this sample size. Normal morphology and TM were unaffected by estrus or vaginitis (P ≥ 0.32), but Hour affected both TM and PM (P < 0.001). In the combined all-timepoints analysis, Season was significant for PM (P < 0.001), morphology (P < 0.001), and TM (P = 0.009), likely driven by between-bull variation by season and highlighting the need for within-bull replication. These preliminary data support further evaluation of estrus expression and vaginitis status as modifiers of the vaginal fluid environment acting on ex vivo sperm progressive motility.