Abstract #367
Section: Animal Health
Session: Animal Health IV
Format: Oral
Day/Time: Tuesday 3:45 PM–4:00 PM
Location: 303
Session: Animal Health IV
Format: Oral
Day/Time: Tuesday 3:45 PM–4:00 PM
Location: 303
# 367
Effects of chloride and sulfate-based diets fed to grazing prepartum dairy cows on postpartum plasma calcium.
P. Melendez*1, V. Zaror2, P. Gaul2, S. Poock1, J. Goff3, 1College of Veterinary Medicine, University of Missouri, Columbia, MO, 2Tribute Dairy, Benton, MO, 3College of Veterinary Medicne, Iowa State University, Ames, IA.
Key Words: calcium, DCAD, grazing
Effects of chloride and sulfate-based diets fed to grazing prepartum dairy cows on postpartum plasma calcium.
P. Melendez*1, V. Zaror2, P. Gaul2, S. Poock1, J. Goff3, 1College of Veterinary Medicine, University of Missouri, Columbia, MO, 2Tribute Dairy, Benton, MO, 3College of Veterinary Medicne, Iowa State University, Ames, IA.
Hypocalcemia is a common metabolic disorder affecting dairy cows during the postpartum period. Lowering dietary cation-anion difference (DCAD) by feeding supplemental chloride or sulfate has been shown to reduce the incidence of hypocalcemia. Different sources of anions have not been extensively compared under practical conditions. The aim of this study was to compare the effect of chloride (Cl) (SoyChlor; commercial chloride supplement) and sulfate (S) (magnesium sulfate) fed to grazing prepartum cows on postpartum plasma Ca. The study was conducted in southeast Missouri, USA in the fall of 2016. Breeds consisted of 20% Holstein, 20% Jersey and 60% crossbred Jersey × Holstein. Cows had been synchronized for breeding such that approximately 600 cows were due to calve in a short period of time. At 30 d before expected parturition, 2 groups of 200 cows each were moved into paddocks where they were fed each day a partial mixed ration (PMR) containing the anionic supplements. Cows had free access to pasture. The PMR would constitute half of the daily DMI. Estimated DCAD for the 2 diets was −25 mEq/kg DM and −26 mEq/kg DM for Cl and S, respectively. Urine samples were collected each week prepartum and checked for pH. Average pre-partum urine pH was 7.71 ± 0.12 and 7.81 ± 0.10 (P = 0.06) for Cl and S, respectively. At calving, 42 cows per group were matched by breed and parity (primiparous, multiparous), and their blood was sampled on d 1, 2, 3, and 7 postpartum. Plasma total Ca was determined by atomic absorption spectroscopy. Data for blood Ca concentration were analyzed by developing a mixed model ANOVA for repeated measures and the best covarinace structure to fit the model. It is concluded that cows fed a TMR based on chloride had a higher calcium concentration at d 1 than cows fed sulfur as a source of anions.
Table 1. Mean (± SEM) plasma calcium (mg/dL) in grazing cattle fed a TMR containing sulfate or chloride
| Sulfate | Chloride | P-value | |
| Primiparous | |||
| d 1 | 7.83+0.3 | 8.37+0.3 | 0.20 |
| d 2 | 8.04+0.3 | 8.33+0.3 | 0.58 |
| d 3 | 7.77+0.3 | 8.38+0.3 | 0.20 |
| d 7 | 8.79+0.3 | 8.64+0.3 | 0.98 |
| Multiparous | |||
| d 1 | 7.30+0.1 | 7.74+0.1 | 0.04 |
| d 2 | 7.56+0.1 | 7.53+0.1 | 0.96 |
| d 3 | 7.63+0.1 | 7.91+0.1 | 0.55 |
| d 7 | 8.07+0.1 | 8.33+0.1 | 0.85 |
Key Words: calcium, DCAD, grazing
