Abstract #39

# 39
Effects of varying prepartum DCAD and calcium concentrations on pre- and postpartum mineral and metabolite concentrations.
A. L. Diehl*1, J. K. Bernard1, S. Tao1, T. N. Smith1, D. J. Kirk2, D. J. McClean2, J. D. Chapman2, 1University of Georgia, Tifton, GA, 2Phibro Animal Health, Corp, Teaneck, NJ.

The objective of this trial was to determine the effects of feeding prepartum diets varying in DCAD and dietary Ca concentrations on blood metabolites and Ca status postpartum. Multiparous Holstein cows (82) were enrolled 28 d before calving and remained on trial through 63 DIM (91 d total). Cows were individually fed 1 of 4 prepartum dietary treatments in a randomized block design experiment with a 2 × 2 factorial arrangement. Treatments provided 2 DCAD concentrations: −22 (NEG) or −3 mEq/100 g DM (NEU); and 2 dietary Ca concentrations: 1.0 or 1.5% of DM. After calving cows were fed the same lactation ration. Urine and blood samples were collected once weekly before calving. Additional blood samples were collected 2 d before expected calving date, immediately after calving, and on 1, 2, and 3 DIM. Data were analyzed using PROC MIXED that included block, DCAD, Ca, interaction of DCAD and Ca, week, and interactions of week and treatments. Significance was declared at P < 0.05 and trends when P > 0.05 and <0.10. Urine pH was lower (P < 0.0001) for NEG compared with NEU and tended to be lower (P = 0.06) for 1.5% compared with 1.0% Ca. Prepartum concentrations of urine Ca were higher (P = 0.02) whereas urine creatinine and urine K were lower (P < 0.01) for NEG compared with NEU. Fractional excretion of Ca (5.91 and 2.86%) and Mg (21.36 and 14.96%) was greater (P < 0.0001) for NEG than NEU, respectively. Plasma total P was higher (P = 0.01) for 1.0% compared with 1.5% Ca. From 0 to 3 DIM, plasma total protein, albumin, total Mg, and ionized Mg concentrations were lower (P < 0.05) for NEG compared with NEU. Interactions of DCAD and DIM (P < 0.05) were observed for plasma total Mg and ionized Mg, as concentrations were similar on 0 and 3 DIM but were higher for NEU on d 1 and 2. An interaction of Ca and DIM was observed for plasma total Ca due to higher concentrations (P < 0.05) at 1 DIM for 1.5%, whereas concentrations were not different at 2 or 3 DIM. These results suggest that feeding −22 mEq/100 g DM prepartum alters plasma and urine mineral concentrations to improve calcium status by 3 DIM compared with feeding −3 mEq/100 g DM. Feeding 1.5% Ca prepartum improved plasma Ca at 1 DIM only.

Key Words: DCAD, calcium, plasma minerals