Minimum Weight and Age of Replacement Heifers for Puberty (Target is 65 percent of Mature Weight) Breed type Age Weight 90% in heat Weight 70% in heat English 13 - 16 Months 675 625 Exotic (European) 13 - 16 Months 776 750 English/exotic cross 13 - 16 Months 750 700 Brahman/English cross 16 - 17 Months 750 725 Brahman 17 - 20 Months 750 725 Comments: Dr. Allan McGinty