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Effects of calcium carbonate supplementation rate on metabolic acid-base status and feed intake of cows with compensated metabolic acidosis.

H. Fujan

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06-22-2020

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Abstract:

M135
Effects of calcium carbonate supplementation rate on metabolic acid-base status and feed intake of cows with compensated metabolic acidosis.
H. Fujan*1, T. Brown2, L. K. Mamedova1, B. J. Bradford1. 1Kansas State University Manhattan, KS, 2Landus Cooperative Ames, IA.

Controversy exists regarding the amount of calcium (Ca) to feed with anionic diets. Potential negative impacts of high Ca diets on dry matter intake (DMI) and diminishment of induced acidosis are 2 areas of interest. In this study, 21 pregnant, nonlactating cows (57.4 � 13.9 d prepartum) completing at least 1 lactation were used in a replicated 3 � 3 Latin square design. All cows were fed a diet providing a DCAD of −6.0 mEq/100 g of DM. Treatments were a) no supplemental Ca carbonate (LOW; 0.6% DM Ca), b) a moderate level of Ca carbonate (MOD; 1.2% DM Ca), or c) a high level of Ca carbonate (HIGH; 1.8% DM Ca). Daily DMI and water intake were recorded. Urine and blood samples were collected 6 h post-feeding. Urine samples were analyzed for pH and concentrations of creatinine, ionized Ca (iCa), and deoxypyridinoline (DPD). Blood samples were analyzed for metabolic indicators of acid-base status (pH, partial pressure of CO2, oxygen saturation, total carbon dioxide, bicarbonate (HCO3), and base excess) as well as iCa, Na, and K using a hand-held biochemical analyzer. Data were analyzed to assess fixed effects of treatment and period and the random effect of cow. There was no effect of treatment on DMI (P = 0.21) or water intake (P = 0.28). Urinary pH increased linearly with increasing Ca carbonate (P = 0.009; 6.41, 6.62 and 6.73 � 0.12 for LOW, MOD and HIGH, respectively). Treatment did not alter urinary Ca excretion (4.75, 5.20 and 5.24 � 0.63 g/d for LOW, MOD and HIGH, respectively; P = 0.67) or DPD (P = 0.45) and had no effect on measures of acid-base status or minerals in blood. DMI was greater in Period 3 vs. 1 (P < 0.01), associated with a decreased urinary pH in Period 3 vs. 1 (P < 0.01). Urinary pH was greater (P = 0.03) for cows on HIGH vs. LOW treatment with no difference in Ca excretion, suggesting dietary carbonate rather than Ca as the influencing factor. When feeding high levels of Ca carbonate to moderately acidified cows, urine pH may not accurately reflect systemic acid-base status. This could compel producers to feed more anionic supplement to maintain a urinary pH target.

Keywords: DCAD, bone, anionic.