Two 2-year experiments were conducted to evaluate the effects of molasses-based creep-feeding supplements fortified with DL-methionine hydroxyl analog (MHA; Exp 1), or different supplemental nitrogen sources (Exp. 2), on growth performance of pre- and post-weaned beef calves. In both experiments, cows and calves were stratified by calving date and randomly assigned to pastures (n=8 and 12 pastures for Exp. 1 and 2, respectively). Treatments were randomly assigned to pastures. In Exp. 1, treatments consisted of no creep-feeding supplementation (NoCreep), creep-feeding supplementation of sugarcane molasses plus 4\% of a 50:50 urea+hot water blend (as-fed; Mol+U) or Mol+U plus 0.22\% of MHA (as-fed; Mol+MHA). In Exp. 2, treatments consisted of NoCreep, creep-feeding supplementation of sugarcane molasses added with 4\% of 50:50 urea+hot water blend (50:50, as-fed; Mol+U) or 20\% cottonseed meal (as-fed; Mol+CSM). Calves were supplemented in cow exclusion areas for 122, 117, 104 and 102 days prior to weaning in years 1 and 2 of Exp. 1 and 2, respectively. In year 2 (Exp. 2), 18 heifers (2 heifers/pen; 3 pens/treatment) were randomly selected for a 17-day post-weaning evaluation and were provided free-choice access to a grain-based concentrate. In Exp. 1, Mol+U calves had similar (P=1.00) voluntary creep-feed supplement intake in year 1, but greater (P<0.01) voluntary creep-feed supplement intake in year 2, compared with Mol+MHA calves. In Exp. 2, voluntary creep-feed supplement intake was not affected (P=0.39) by treatment. In Exp. 1, but not in Exp. 2, creep-feeding supplementation increased (P <= 0.01) calf BW at weaning and pre-weaning ADG compared with NoCreep calves. Calves supplemented with MHA had lesser (P=0.03) pre-weaning ADG than Mol+U calves. In Exp. 2, nitrogen source added to creep-feed supplement did not affect (P=0.15) calf pre-weaning ADG. Additionally, pre-weaning creep-feeding supplementation of heifers did not affect (P >= 0.25) post-weaning growth performance or plasma concentrations of haptoglobin and fibrinogen during the receiving period. At weaning, heifers fed Mol+U had greater (P=0.03) plasma concentrations of ceruloplasmin (Cp) than Mol+CSM heifers (23.8 versus 18.7 +/- 1.62 mg/dL, respectively), with NoCreep heifers being intermediate. On day 9, relative to weaning, Mol+U heifers had greater (P=0.03) plasma Cp concentrations than NoCreep heifers (31.6 versus 26.6 +/- 1.62 mg/dL, respectively), with Mol+CSM heifers being intermediate. In conclusion, molasses-based creep-feed supplements increased pre-weaning growth performance of calves in Exp. 1, but not in Exp. 2, and did not affect post-weaning growth performance of heifers. (C) 2012 Elsevier B.V. All rights reserved.