All infants were divided into two groups with the sequence of outpatient : lactoferrin-fortified formula milk group ( fortified group , FG , containing lactoferrin 38mg/100g milk and iron element 4mg/100g milk ) and no lactoferrin fortified milk ( control group , CG , containing lactoferrin 0mg/100g milk and iron element 4mg/100g milk ) for 3mo .