Physiological and age-related neck morphometric variability in Holstein dairy cows: A pilot study

The neck region of dairy cows remains poorly characterised despite its relevance for conformation assessment, phenotyping and precision livestock farming (PLF) applications. This pilot study aimed to describe regional cervical morphometric variability in Holstein dairy cows and to evaluate associations with lactation stage and chronological age. Thirty-five Italian Holstein cows (heifers, lactating and dry) were measured twice under commercial-like conditions (n = 70 observations). Minimum, mid and maximum neck girths, thoracic girth and body condition score (BCS) were recorded using a standardised manual protocol. Third-degree polynomial regression models and Pearson correlations were used to assess relationships with days in milk (DIM) and age. Minimum and mid-neck girths showed significant non-linear associations with DIM (R2 = 0.322 and 0.382; P < 0.01), characterised by early-lactation reductions and late-lactation increases. Maximum neck girth showed a weak and non-significant association with DIM (R2 = 0.197; P = 0.068) but was strongly age-dependent (R2 = 0.407; P < 0.0001). Thoracic girth was primarily related to age (R2 = 0.701; P < 0.0001) and moderately associated with DIM (R2 = 0.242; P = 0.029). Cervical measures showed only weak correlations with body weight. This study provides a preliminary anatomically differentiated description of cervical morphometry in dairy cows, highlighting region-specific morphometric variation associated with physiological stage and age and establishing an initial reference framework for future studies on bovine morphometric phenotyping and PLF applications.