Multivariate phenotyping reveals thermoregulatory patterns in crossbred cattle

Improving the adaptation of beef cattle production to climate change requires crossbreeding strategies that enhance the ability of animals to maintain thermal stability under hot conditions. The objective of this exploratory study was to assess how coat characteristics are associated with rectal-temperature variation and to identify thermoregulatory patterns in Red Angus × Nelore crossbred cattle raised under tropical conditions. Thirty clinically healthy crossbred bulls from two genetic compositions (½ Red Angus × ½ Nelore and ¾ Red Angus × ¼ Nelore) were evaluated at 210 and 360 days of age. Morphological, physiological, and environmental variables were recorded, including coat thickness, hair length, hair quantity, hair density, and rectal temperatures measured in the morning and afternoon. Univariate comparisons did not detect differences (p > 0.05) between the genetic groups in the evaluated coat traits or rectal temperatures, indicating substantial overlap between genetic compositions. In an exploratory logistic model developed to discriminate the two genetic groups, rectal temperature was positively associated with group classification [odds ratio (OR) = 1.41, p = 0.023], whereas hair length showed a negative association (OR = 0.53, p < 0.001), indicating that morphological and physiological traits jointly contributed to the observed differentiation. Correlation analysis showed that thicker coats tended to contain fewer and less densely distributed hairs, whereas hair quantity and density were strongly and positively associated, suggesting compensatory coat architectures. The exploratory clustering solutions suggested four candidate coat-related configurations: (i) short, dense coats and (ii) thick but less dense coats, both associated with lower daily rectal-temperature variation; and (iii) intermediate coats and (iv) long, dense coats, associated with greater thermal fluctuation. Although some overlap among clusters was observed, these configurations provide an exploratory basis for understanding how combinations of coat characteristics may influence thermoregulatory responses. The findings indicate that thermal regulation in crossbred cattle is better understood through combinations of morphological traits than through isolated characteristics. Future studies with larger, independent populations and additional physiological and productive measurements are needed to confirm the consistency and broader applicability of these patterns.