Morphometric structure and age-related growth of body and udder traits in Khuzestani buffalo

Body measurements in buffalo serve as fundamental morphometric indicators that provide cost-effective and practical insights into growth performance, productive capacity, reproductive status, and overall breeding value. Accordingly, this study presents the first systematic morphometric evaluation of body and udder traits in Khuzestani buffaloes maintained within the Safiabad (Dezful) nucleus herd. Direct measurements were collected in 2025 from 104 female buffaloes (18 months to 13 years old), including nulliparous, primiparous, and multiparous animals. Twelve body conformation traits-including wither and rump height (WH, RH), body, spine, heart, and rump length (BL, SL, HL, RL), heart, barrel, and rump girth (HG, BG, RG), and hip, rump, and shoulder width (HW, RW, SW)-along with key udder morphometric traits (fore and rear teat length: FTL, RTL; fore teat-udder attachment distance: FTUAD; rear udder width: RUW; vulva-udder distance: VUD) were analyzed. Age-related trajectories were modeled using polynomial regressions selected via BIC, and marginal means were estimated. Multivariate structure was explored through principal component analysis (PCA) and Exploratory Graph Analysis (EGA). Body traits were highly integrated, displaying strong positive correlations among girth and trunk measures (e.g., HG-HL = 0.91), with rapid growth during early adulthood (height peaking at ~ 5-6 years; overall growth accelerating until ~ 4 years). Udder traits were more variable but exhibited coherent patterns; udder size increased nonlinearly with age, peaking near 11 years, and enlarged further with active lactation. PCA revealed a dominant size component (PC1 explaining 71.7% of total variation when combined; body-only PC1 = 82.8%; udder PC1 = 59.1%). EGA identified two distinct latent communities separating body conformation and udder morphology, supporting their partial developmental and functional independence. These results establish baseline morphometrics and growth trajectories for Khuzestani buffalo, providing practical value for selection, management, and the development of udder-specific indices in genetic improvement programs.