The animals used in this study were purebred Angus yearling heifers and 2-year-old heifers, held from their first
breeding season (n ¼ 99) between 13 and 27 months of age and cows (n ¼ 43) between 48 and 74 months of age
housed at the Upper Piedmont Beef Cattle Research Station
located in Reidsville, NC, USA. The nulliparous and multiparous animals were maintained on a pasture sepa- rated from each other. The animals were fed coastal Bermuda grass hay and pasture and had ad libitum access to water and free-choice mineral mix.