Negative dietary cation-anion difference and amount of calcium in prepartum diets: Effects on urine and serum minerals

Negative dietary cation-anion difference (DCAD) diets fed prepartum induce a compensated metabolic acidosis, which stimulates metabolic Ca flux before calving and decreases clinical and subclinical hypocalcemia after calving. Effects of low or high dietary Ca in these diets are unclear. Our objective was to determine the effects of inducing a prepartum metabolic acidosis and the amount of dietary Ca on urinary mineral excretion and serum mineral concentrations during the transition period in multiparous Holstein cows (n = 81). Treatment diets fed during the last 28 d before calving were (1) positive DCAD, +6 mEq/100 g of dry matter (DM), target urine pH >7.5, low dietary Ca (0.40% DM; CON); (2) negative DCAD, −24 mEq/100 g of DM, target urine pH 5.5 to 6.0, low dietary Ca (0.40% DM; ND); or (3) negative DCAD, −24 mEq/100 g of DM, target urine pH 5.5 to 6.0, high dietary Ca (2.0% DM; NDCA). Urine was sampled on −21, −14, −7, +1, +2, and +7 d relative to calving. Blood samples were collected on d −30, −21, −14, −7, −4, −2, −1, 0, 1, 2, and 4 relative to parturition. Preplanned treatment contrasts were (1) CON versus ND and NDCA, and (2) ND versus NDCA. Cows fed ND or NDCA had increased urinary volume and excretion of Ca, Cl, and SO4−2, along with decreased excretion of K. Supplementation of Ca to the acidogenic diet increased urinary excretion of Ca at d −21, but this difference lessened as cows approached parturition. Additional Ca increased prepartum urinary excretion of K and Cl. Differences in excretion decreased quickly after parturition, although urinary excretion of Cl remained greater for cows previously fed negative DCAD diets. Acidogenic diets increased serum K and Cl concentrations prepartum. Supplemental Ca decreased serum P relative to ND. During d 0 to 4, serum P and K were greater for cows fed ND or NDCA than for cows fed CON; these differences disappeared by d 4. Acidogenic diets increased serum Ca by increasing Ca flux and excretion in urine. Supplemental Ca in the acidogenic diet modestly increased Ca excretion early in the close-up period

Effect of Prepartum DCAD Strategy and Level of Dietary Calcium on Postpartum Calcium Status and Performance of Multiparous Holstein Cows

Periparturient hypocalcemia can be mitigated by reducing prepartum dietary DCAD; however, neither the extent of DCAD adjustment nor the level of dietary Ca fed with negative DCAD have been evaluated fully. This project aimed to compare the effects of two levels of prepartum dietary anion supplementation (urinary pH), two levels of dietary calcium, and the interactions, on parameters of calcium metabolism, health, and milk performance of transition dairy cows

2021 Cornell Nutrition Conference - complete proceedings of manuscripts

Department of Animal Scienc