Simple linear regression and positive correlation between tCa and iCa (R = 0.84, R2 = 0.712 P < 0.001) tCa = 3.2 + 1.23*iCa for cows fed prepartum (Tr1) DCAD (0.0, -100, -180) there is positive linear relationship tCa and iCa p < 0.05.