The longissimus dorsi ultrasound evaluations influenced by stocking density in beef heifers

Greater stocking density may negatively affect beef cattle’s growth. The longissimus dorsi ultrasound is a method for assessing their performances in vivo evaluating fat (intramuscular fat (IMF) and backfat thickness (BFT)) and muscle (muscle thickness (DEPTH) and ribeye area (RIBEYE)) components. European recommendations suggest a space from 2.4 to 5.5 m²/animal. However, a ≥13 m²/animal is suggested for heavy animals to reduce group stress. The aim of the study was to evaluate beef heifers housed at two stocking densities using longissimus dorsi ultrasound. A total of 54 Charolais heifers were enrolled (protocol number of ethical approvals 17498/2024). Animals were randomly divided into indoor boxes at arrival composing: high-stocking density group (HIGH_D; 5.54 m2/animal, N=26) routinely adopted in the farm, and low-stocking density group (LOW_D; 10.3 m2/animal, N=28) as a compromise between animals’ and farmer’s needs. The longissimus dorsi ultrasound evaluations were performed at arrival (D0), and after 30, 60, 90 and 120 days (D30, D60, D90, and D120) until slaughtering. The animal body weight (BW) was measured at D0, D60, and D120 and average daily gain (ADG; Kg/day) was then calculated among time-points. Finally, the carcass yield was obtained by the slaughterhouse. Statistical analysis was conducted with linear mixed models, a p≤0.05 was used as significant, and 0.05