A Dairy Herd Case Investigation with Very Low Dietary Cation-Anion Difference in Prepartum Dairy Cows.

Pedro Melendez,Scott Poock

doi:10.3389/fnut.2017.00026

Abstract

During the periparturient period, subclinical hypocalcemia (total plasma Ca concentration <2.0 mmol/l) is a potential problem for the dairy cow; consequently, its prevention is essential for success of fertility and productive performance. Dietary cation–anion difference (DCAD) has been defined as the difference in milliequivalents of cations (Na, K) and anions (Cl, S) per kilogram of dry matter (DM) and has a direct impact on blood acid–base metabolism. Diets rich in K and Na induce metabolic alkalosis, interfering with tissue sensitivity to parathyroid hormone, and diets rich in Cl and S (anionic salts) cause metabolic acidosis, reducing the risk of hypocalcemia. Consequently, the use of anionic salts has become a popular method to prevent hypocalcemia in dairy cattle. Monitoring diets with anionic salts can be done by measuring urine pH, with optimal values between 6.2 and 6.8 for Holstein cows. The objective of this report is to present a herd case investigation involving a dairy farm feeding a very low DCAD (−143 mEq/kg DM), expecting improved Ca homeostasis. The diet of −143 mEq/kg (urine pH 5.2–5.8) was changed to a diet with −53 mEq/kg DM (urine pH 6.2–6.8). Blood samples were taken at the time of calving for 10 cows that calved before and then for 10 cows that calved after changing the diet. Cows with extremely low DCAD had Ca concentrations of 2.11 ± 0.22 mmol/l and cows with a more moderated DCAD, 2.11 ± 0.16 mmol/l (P > 0.05). Several other blood metabolites (P, Mg, Na, K, Cl, albumin, globulins, blood urea nitrogen, creatinine, and GGT) were also similar between groups. This very low DCAD during the prepartum period may severely compromise animal physiology unnecessarily, with little advantage over normal calcium concentrations at parturition, when compared with a less negative DCAD (−53 mEq/kg DM). Feeding a less negative DCAD ration (−53 mEq/kg DM) did not decrease plasma Ca levels right after parturition compared to a DCAD ration of −143 mEq/kg DM, reinforcing the lack of benefit of a more negative DCAD.

Highlights

On October 1, 2015, the University of Missouri dairy herd initiated a more systematic cow health monitoring program
Hypocalcemia is a potential problem in the dairy cow, as a result of the sudden drain of Ca to colostrum at the onset of lactation
There are few studies demonstrating that feeding a negative dietary cation–anion difference (DCAD) for more than 40 days would negatively affect the performance of the periparturient dairy cow and her offspring [16, 17]

Summary

Introduction

On October 1, 2015, the University of Missouri dairy herd initiated a more systematic cow health monitoring program. At 3 weeks before expected parturition, dry cows were moved to a prepartum lot where cows were fed anionic salts (Tables 1 and 2) to prevent hypocalcemia and related disorders. On October 21, 2015, a urine sample from nine cows (30%) of the prepartum cows was obtained according to standard recommendations. 10–50% of cows may develop subclinical hypocalcemia (1.25–2.0 mmol/l) up to 10 days postpartum, affecting organs that have smooth muscle function, such as the uterus, rumen, and the abomasum [2, 5]. Hypocalcemia is a significant risk factor for dystocia, retained fetal membranes, metritis, uterine prolapse, displacement of the abomasum, clinical ketosis, and fatty liver [6] These disorders have been associated with subsequent infertility [2, 6]

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Discussion

Conclusion