Puberty attainment (±SEM) of heifers receiving subcutaneous injections containing 250 mg of bovine ST (BST; sometribove zinc; n = 25; Posilac, Elanco, Greenfield, IN) or 5 mL of saline (0.9%; control; n = 25). Treatments were administered every 14 d beginning on d 14 until d 196 of the experimental period (d 0 to 210). Heifers were considered pubertal once plasma progesterone concentrations were greater than 1.0 ng/mL for 2 consecutive weeks, and puberty attainment was declared at the second week of increased progesterone. A treatment × day interaction was detected (P = 0.04). Treatment comparison within days: **P < 0.01, *P = 0.03, and †P = 0.10.