Effects of trace mineral-fortified, limit-fed preweaning supplements on performance of pre- and postweaned beef calves.

Two studies were conducted to evaluate the effects of preweaning limit-fed creep feed (LFC) with or without trace mineral fortification on trace mineral status and pre- and postweaning growth performance of beef calves. At 102 (Exp. 1) and 97 (Exp. 2) d before weaning, Brahman × British cow-calf pairs (calf age = 142 ± 20 d) were stratified by calving date and randomly allocated into 1 of 8 pastures (approximately 17 pairs/pasture annually; calf BW = 104 ± 5 and 132 ± 25 kg in Exp. 1 and 2, respectively). Treatments were randomly assigned to pastures and consisted of no calf supplementation (Nonsup; 2 pastures/experiment) and limit-fed supplements with (MIN+; 3 pastures/experiment) or without (MIN-; 3 pastures/experiment) trace mineral fortification. Supplements were limit fed in cow exclusion areas 3 times weekly in amounts to provide 0.23 kg/calf daily. In Exp. 1, supplements consisted of compressed cubes (approximately 3.0 by 6.5 cm) whereas in Exp. 2, supplements were offered in a loose meal mixture. At weaning, 15 and 9 heifers/treatment in Exp. 1 and 2, respectively, were randomly selected to be transported (Exp. 1) or to receive an intramuscular injection of porcine red blood cells (PRBC; Exp. 2), each immediately preceding a 28-d feedlot receiving evaluation. In Exp. 1 but not in Exp. 2, LCF increased weaning BW (P = 0.05) compared with Nonsup calves (229 vs. 219 kg; SEM = 4.2). Trace mineral fortification of creep feed decreased DMI of LFC (P < 0.001 and 0.11 in Exp. 1 and 2, respectively) but did not affect (P ≥ 0.53) weaning BW of LFC calves. In Exp. 2 but not Exp. 1, Calves provided LFC had greater (P = 0.040) DMI during the first week postweaning, which was the result of greater (P = 0.040) voluntary DMI of concentrate, compared with Nonsup calves, during this period. In Exp. 2 but not in Exp. 1 (P ≥ 0.12), MIN+ increased (P ≤ 0.04) liver concentrations of Co, Cu, and Se compared with MIN- calves. Preweaning treatment had no effect on serum anti-PRBC immunoglobulin titers and plasma concentrations of haptoglobin and ceruloplasmin (P ≥ 0.37). Thus, limit-fed creep-feed supplements 1) increased calf weaning BW (Exp. 1), 2) enhanced trace mineral status of weaned calves when supplements were fortified with trace minerals (Exp. 2), and 3) increased voluntary DMI during the first week of the feedlot receiving period (Exp. 2).