Presentation date: 2006-05-09Graduation date: 2006Twenty-six Holstein and 18 Jersey multiparous cows in a randomized block design were assigned by calving date and breed to a non-anionic prepartum diet (CTRL) or a treatment diet containing a commercial anionic salt supplement (Animate®). Control and treatment diets were formulated to a dietary anion-cation difference (DCAD) of 21.3 and -14.3 meq/100 grams. The hypothesis that prepartum anionic diets and level of adiposity, measured by body condition score (BCS) and body weight, positively affect pre and postpartum dry matter intake (DMI) and energy balance were tested. We evaluated several markers of the mobilization of adipose tissue, including plasma β- hydroxybuterate (BHB), non-esterified fatty acid (NEFA), and glucose, and the serial expression of cortisol, adiponectin, tumour necrosis factor-alpha (TNF-α), and insulin, and their effect on energy balance. The effect of anionic prepartum diets on post-parturient metabolic disorders, body weight loss, and subsequent milk production were also investigated.Cows were BCS scored prior to parturition and assigned to five prepartum groups. The effects of prepartum dietary treatment by BCS were evaluated for serum concentrations of cortisol, diponectin, insulin, TNF-α, calcium and magnesium from day -21 prepartartum through d 21 days postpartum. No difference in prepartum or postpartum energy balance was observed based on prepartum diet. Cows receiving the anionic diet returned to positive energy balance faster than CTRL. DMI by day was 3.71 kg higher for Holsteins fed the anionic diet. Milk yield for Holsteins fed the anionic diet was 3.22 kg. more than CTRL. Holsteins fed the anionic prepartum diet produced 46.2 kg. ECM compared to 39.5 kg. ECM for the control diet. Milk production of Jersey cows did not differ based on prepartum diet. Plasma NEFA, cortisol, and adiponectin concentrations were unaffected by dietary treatment, nor by BCS. BHB concentrations were not directly affected by dietary treatment. Interactions for BCS by treatment were observed for BHB and TNF-α, with a crossover points at BCS 3.5. An interaction for plasma insulin by BCS was observed. No differences based on prepartum diet were observed in the incidence of milk fever, retained placenta, nor clinical mastitis in the first 21 days of lactation.