To investigate the effects of rumen bypass fat on the energy negative balance in the postpartum cows,48 health dairy cows(3~4 weeks before calving) were selected and arranged into test and control groups on according to the principal of sameness in age,bodyweight,calving times,body condition scoring and expected date of calving,and the last milking yield or her mother's milking yield,24 cows in each group.The bypass fat additives(Wanshanbao) were added in the total mixed ration(TMR) of test group for 300 g ...