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. 2025 Aug 20:12:1649751.
doi: 10.3389/fvets.2025.1649751. eCollection 2025.

Associations between prepartum urine pH and periparturient blood calcium concentrations in multiparous Holstein cows

Jesse P Goff  1 , Pedro Melendez  2 , Julian A Bartolome  3 , Thomas R Overton  4 , Brittany M Leno  4 , Geneva Graef  4 , James K Drackley  5 , Kristen M Glosson  5 , Xiangfei Zhang  5 , Stephen J LeBlanc  6 , Rita Couto-Serrenho  6 , José E P Santos  7 , Camilo Lopera  7 , Roney Zimpel  7 , Rachael M Rodney  8 , Ian J Lean  8
Affiliations

Associations between prepartum urine pH and periparturient blood calcium concentrations in multiparous Holstein cows

Jesse P Goff et al. Front Vet Sci. .

Abstract

Introduction: Metabolic alkalosis induced by prepartum diet cations impairs Ca homeostasis in the periparturient cow. Adding anions to prepartum diets reduces blood pH improving periparturient Ca homeostasis. Urine pH generally reflects blood pH and is practical to measure on farm. The degree to which urine should be acidified to increase periparturient blood Ca concentration is not well defined.

Materials and methods: Prepartum urine pH and periparturient blood Ca concentrations determined in 660 multiparous Holstein cows from 9 studies were analyzed. Least Square Means of the lowest blood Ca concentration (Ca nadir) observed in cows within 6 urine pH categories (≤ 5.75, 5.76 to 6.25, 6.26 to 6.75, 6.76 to 7.25, 7.26 to 7.75, and ≥ 7.76) were determined. Data were analyzed across all 660 cows and then by parity.

Results: Across all cows, the Ca nadir was lowest and the incidence of cows with Ca nadir < 2.00 mM, indicative of subclinical hypocalcemia (SCH), was greatest when urine pH was ≥ 7.76. Mean Ca nadir increased in all cows with urine pH < 7.75. There was no significant difference in Ca nadir or % of cows with SCH when prepartum urine pH was < 7.75. This was also the case for 2nd and 3rd parity cows. However, in ≥ 4th parity cows, those with urine pH between 6.26 and 6.75 had significantly higher Ca nadir than cows with urine pH above 7.25 or below 5.75. Calcium nadir and blood Ca concentrations at 2 days in milk (DIM) were highly correlated (r = + 0.58), and blood Ca concentrations at 2 and 4 DIM were moderately correlated (r = + 0.43). Blood Ca concentration at 4 DIM was weakly associated with Ca nadir (r = + 0.30).

Discussion: These analyses support acidification of cows to achieve prepartum urine pH below 7.75 to increase blood Ca nadir for 2nd and 3rd parity cows. For ≥ 4th parity cows, the highest blood Ca nadir was observed with urine pH below 7.25 and above 5.75. For ≥ 4th parity cows, urine pH below 5.75 was associated with significantly lower blood Ca nadir.

Keywords: DCAD; acidification; hypocalcemia; milk fever; urine pH.

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Conflict of interest statement

JG: Invented Soychlor, an anionic supplement produced by Landus Farmer's Cooperative. He was a paid consultant of the cooperative and has long suggested urine pH of close-up dry cows is most effective when urine pH is between 6 and 6.8. He no longer consults for Landus Cooperative. He is a paid consultant on the scientific advisory board for GLC Minerals, a producer of magnesium hydroxide for cattle. He owns Accunutrition, a company that invented a Solanum glaucophyllum calcium bolus to reduce hypocalcemia after calving and is also using such plant material for application to human medicine. He owns GlycoMyr, a company that produces a vitamin supplement for piglets. JG owns Stagecoach Veterinary Services, Ames, IA. IL: Ian Lean imported anionic feed to Australia but has not done this for approximately 10 years. He uses anionic feeds and sells these feeds and many others as part of formulated diets. He has not been a retained consultant to companies but undertakes consultancy work on behalf of many government and industry organizations. He is managing director of Scibus and Cows-R-Us and a board member on many industry bodies. He has conducted considerable research into calcium metabolism and the role of cation anion difference in this. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
The mixed model predicted nadir concentration of total Ca in blood postpartum according to urine pH prepartum and parity group of 660 cows from 9 experimental studies. The mixed model included the fixed effects of urine pH linear (p < 0.001), urine pH quadratic (p < 0.001) and parity group (p < 0.001) and the random effect of experimental study.
Figure 2
Figure 2
Correlation between blood Ca concentration nadir observed after parturition and blood Ca concentration observed at 2 DIM in multiparous cows. Pearson coefficient of correlation = +0.589.
Figure 3
Figure 3
Correlation between blood Ca concentration nadir observed after parturition and blood Ca concentration observed at 4 DIM in multiparous cows. Pearson coefficient of correlation = +0.30.
Figure 4
Figure 4
Correlation between blood Ca concentration observed at 2 DIM and blood Ca concentration observed at 4 DIM in multiparous cows. Pearson coefficient of correlation = +0.428.
See this image and copyright information in PMC

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