Uterine horn echotexture during the first follicular wave after synchronized ovulation and its relationship with antral follicle count in Holstein cows.

The bovine uterus undergoes marked structural remodeling during the early luteal phase, yet quantitative information on post-ovulatory changes in uterine horn echotexture remains limited. This study characterized uterine horn echotexture during the first follicular wave following synchronized ovulation in Holstein cows and evaluated its association with uterine horn classification and antral follicle count (AFC). Thirty-six Holstein cows (Bos taurus; parity 2-6; 60-65 days in milk) synchronized using an Ovsynch protocol were examined on Days 0, 1, 3, 6, and 9 after ultrasonographically confirmed ovulation. Mean gray level (MGL), gradient (GR), homogeneity (HOM), and contrast (CON) were quantified in both uterine horns (360 observations) and analyzed using linear mixed-effects models. AFC was defined as the mean number of follicles ≥ 3 mm across five examinations. All echotexture parameters changed significantly over time (p ≤ 0.007); MGL, GR, and CON increased, whereas HOM decreased. No significant differences occurred between ipsilateral and contralateral horns (p ≥ 0.094), and horn-level variance within cows remained below 5.7%. Anatomically, MGL was 3.05 units higher in the right horn (p = 0.043), although 27 of 36 ovulations occurred in the right ovary, limiting separation of anatomical from functional laterality. AFC was associated only with MGL; each 10-follicle increase corresponded to a 4.84-unit increase (95% CI: 1.51-8.17; p = 0.006), with no day × AFC interaction (p = 0.184). Quantitative echotexture analysis provides an objective approach for monitoring physiological uterine remodeling, whereas ovarian follicle reserve shows a modest, parameter-specific association with uterine echogenicity.