Relationship among morphometric traits of the pelvis, perineum, and urovagina in Spanish Holstein dairy cattle

Background This study evaluated pelvic and perineal anatomical traits in dairy cows to determine whether morphological conformation is associated with urovagina (UV). The traits assessed were body condition score (BCS), caudal rump height (CRH), withers height (WH), coxal width (CW), ischial width (IW), rump length (RL), rump angle (RA), vulva angle (VA), vulvar commissure length (VL), vulvar commissure length below the caudal edge of the pelvic floor (VBPL), and its relative percentage (VBP%). A total of 1 445 cows were evaluated for the occurrence of UV, and 34 cases were identified. Morphometric traits were assessed in 1 038 lactating cows from 18 dairy farms in central Spain. Population means were calculated, and cows were classified into four groups according to RA: G1 (RA ≤ 0°), G2 (0° < RA ≤ 3°), G3 (3° < RA ≤ 8°), and G4 (RA > 8°), to evaluate associations between RA, the remaining morphometric traits, and UV. A cluster analysis was performed to identify morphological types, and the morphometric characteristics of the 34 cows diagnosed with UV were compared with those of cows without UV. Results Overall, 22.6% of cows presented horizontal or elevated ischia (G1; RA ≤ 0°), considered a suboptimal pelvic conformation. The prevalence of UV was 2.35%. Compared with cows without UV, affected animals seemed to show a lower RA (3.32° ± 4.11 vs. 4.77° ± 4.37; P = 0.057), greater VA (119.76° ± 14.42 vs. 114.85° ± 13.08; P = 0.032), and lower VBP % (57.52 ± 18.47 vs. 72.96 ± 18.07; P = 0.0001). Cluster analysis identified four morphological groups: small–narrow, small–wide, tall–narrow, and tall–wide cows. Cluster 4 (tall–wide) exhibited the most horizontal RA (2.94° ± 4.2°; P < 0.0001). Conclusions Dairy cows with a more horizontal or negative RA tend to have a lower VBP % and a greater VA, anatomical characteristics that were associated with UV in this study. These findings highlight the relevance of pelvic and perineal conformation as potential indicators of susceptibility to this condition.