Body weight, coat traits and thermal environment as determinants of intake and performance in Bos taurus beef cattle

This study aimed to evaluate how morphological traits associated with thermal environmental adaptation influence feed and water intake in Caracu young bulls under tropical conditions. We investigate (1) the association of body weight with coat traits related to heat adaptation; and (2) the relationship among body weight, coat traits and thermal environment on feed intake, water intake, and average daily gain. Ninety-four animals (mean ± SD; 287 ± 22 days old) participated in two Feed Efficiency Tests (FET; 2024 and 2025) over 70-day. Body weight (BW) and coat traits (hide thickness, hair length and hair colour) were measured every fourteen days, while daily water and dry matter intake (DMI) were continuously recorded. Animals were categorized as heavy (n=27; BW: 315.5 ± 18.0kg), intermediate (n=31; BW: 271.5 ± 12.1kg), and light (n=36; BW: 222 ± 23.6kg) based on initial BW. Environmental data were used to calculate adjusted temperature–humidity index (THIadj). Different linear mixed models were used (1) to evaluate the association of body weight category and days on FET on coat traits; (2) to identify factors associated with dry matter intake and water intake; and (3) to assess the relationships between days on FET and intake variables. Light animals showed lower (p≤0.05) hide thickness and longer short hair (p=0.004) than heavy and intermediate animals, whereas long hair length and coat colour were not associated with body weight category (p≥0.05). For all animals, hide thickness increased with days on FET (p≤0.001), whereas long hair length (p≤0.001) and coat colour decreased over time (p≤0.001). Light and intermediate animals showed greater (p≤0.001) average daily gain than heavier animals. DMI decreased with increasing THIadj (p≤0.001) and coat colour score (p≤0.001) but increased with water intake (p≤0.001) and hide thickness (p≤0.005). Water intake increased with THIadj (p≤0.001), hide thickness (p≤0.001), and dry matter intake (p≤0.001), while decreasing with coat colour (p≤0.001). BW category was no associated (p≥0.05) with water intake. Our findings indicate that body weight, days on FET, coat traits, and thermal environment were significant predictors of intake in Caracu cattle. Body weight and days on FET were associated with variation in coat traits, whereas higher THIadj was associated with lower feed intake and greater water intake.