Lay Summary Replacement beef heifers are often reared in drylots to facilitate feeding and management, or to intensify beef production as availability of grazing areas becomes limited. Our research group demonstrated that rearing heifers in drylots with high stocking density (14 m2/heifer) delayed puberty attainment compared with pasture-based systems, largely due to chronic stress associated with confinement. This experiment evaluated growth, stress-related physiological responses, and puberty attainment of beef heifers reared in drylots with decreasing stocking densities (14, 28, or 42 m2/heifer), and compared them with heifers reared on pasture. All heifers received the same diet to ensure that differences in reproductive development were not driven by nutrition. Heifers reared at the highest stocking density (14 m2/heifer) experienced greater indicators of chronic stress and delayed puberty compared with pasture heifers, despite similar growth rates. Reducing the stocking density in drylot pens attenuated physiological indicators of chronic stress but did not improve puberty attainment relative to pasture heifers. Therefore, reducing stocking density of drylot heifers was insufficient to overcome the negative effects of confinement on reproductive development, despite improving stress-related physiological responses. Management strategies beyond stocking density reduction should be considered to improve welfare and reproductive outcomes in intensive heifer development systems.
Prado et al. (Mon,) studied this question.