EFFECTS OF VARYING DCAD AND CALCIUM CONCENTRATION IN PREPARTUM DIETS ON CALCIUM STATUS, HEALTH AND PERFORMANCE IN COWS AND ON NEWBORN CALF ACID-BASE BALANCE By ASHLEY DIEHL

PREPARTUM DIETS ON CALCIUM STATUS, HEALTH AND PERFORMANCE IN COWS AND ON NEWBORN CALF ACID-BASE BALANCE By ASHLEY DIEHL (Under the Direction of John Bernard) ABSTRACT The objective of this trial was to determine the effects of feeding a partial or fully acidified diet (-3 compared with -22 mEq/100 g DM) supplemented with 1.3 or 1.8% calcium (Ca) during the prepartum period on blood Ca, postpartum performance and health as well as newborn calf acid-base status. Feeding the fully acidified diet or 1.3% Ca decreased dry matter intake (DMI) prepartum. Milk yield increased after 45 days in milk (DIM) for cows fed the fully acidified diet. Plasma and urine minerals were altered to improved Ca status by 3 DIM for cows fed fully acidified diets, while 1.8% Ca supplementation improved plasma calcium concentration at 1 DIM only. Feeding 1.8% Ca decreased colostrum quality compared to 1.3% Ca. There was no effect on blood mineral or gas concentrations of calves from feeding a partial or fully acidified diet prepartum.