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A total of 177 Nelore heifers were examined by ultrasonography to determine the presence or absence of a corpus luteum (CL) and received a 3mg norgestomet ear implant plus 2mg of estradiol benzoate i.m. On Day 8, implants were removed and 150μg of d-cloprostenol i.m. was administered. At the time of norgestomet implant removal, heifers with or without CL at the time of initiating treatment were assigned equally and by replicate to be treated with 0IU (n=87) or 400IU (n=90) eCG i.m. All heifers received 1mg of EB i.m. on Day 9 and were submitted to fixed-time artificial insemination (FTAI) 30–34h later. The addition of eCG increased the diameter of the largest follicle (LF) at FTAI (10.6±0.2mm vs. 9.5±0.2mm; P=0.003; mean±SEM), the final growth rate of the LF (1.14±0.1mm/day vs. 0.64±0.1mm/day; P=0.0009), ovulation rate [94.4% (85/90) vs. 73.6% (64/87); P=0.0006], the diameter of the CL at Day 15 (15.5 …