Ability of milk pH to predict subclinical mastitis and intramammary infection in quarters from lactating dairy cattle

Abstract

Milk pH is increased in lactating dairy cattle with subclinical mastitis (SCM) and intramammary infection (IMI). We hypothesized that milk pH testing provides an accurate, low-cost, and practical on-farm method for diagnosing SCM and IMI. The main objective was to evaluate the clinical utility of measuring milk pH using 3 tests of increasing pH resolution: Multistix 10 SG Reagent Strips for Urinalysis (Multistix strips, Bayer HealthCare Inc., Elkhart, IN), pH Hydrion paper (Microessential Laboratory, Brooklyn, NY), and Piccolo plus pH meter (Hanna Instruments, Woonsocket, RI), for diagnosing SCM and IMI in dairy cattle. Quarter foremilk samples were collected from 115 dairy cows at dry off and 92 fresh cows within 4 to 7 d postcalving. Quarter somatic cell count (SCC) was measured using a DeLaval cell counter (DeLaval, Tumba, Sweden), with SCM defined as SCC >200,000 cells/mL and IMI defined as SCC >100,000 cells/mL and the presence of microorganisms at ≥10 cfu/mL of milk. Milk pH was measured at 37°C using the 3 test methods. The Hydrion pH paper performed poorly in diagnosing SCM and IMI. Receiver operating curve analysis provided optimal pH cutpoints for diagnosing SCM for the pH meter (dry off, ≥6.67; freshening, ≥6.52) and Multistix strips (dry off and freshening, ≥7.0). Test performance of the pH meter and Multistix strips was poor to fair based on area under the receiver operating curve, sensitivity, specificity, positive likelihood ratio, and kappa coefficient. The pH meter and Multistix strips performed poorly in diagnosing IMI at dry off and freshening. We concluded that milk pH does not provide a clinically useful method for diagnosing SCM or IMI in dairy cattle.

Hycole Doe Milk Properties and Kit Growth

“…The milk pH is a popular indirect indicator of mastitis [21,22]. The physiochemical quality of milk from different goat breeds was analyzed by Vacca et al [32].…”

“…With mastitis, there is an increased number of leukocytes since they are a part of the defense system in the mammary gland. The pH increase is also related to the severity of mammary gland inflammation [21,22].…”

Pharmacokinetics and pharmacodynamics of intramammary cefquinome in lactating goats with and without experimentally inducedStaphylococcus aureusmastitis

“…Mean milk pH values increased to 7.2 after experimental induction of S . aureus mastitis; the increase in milk pH has been attributed to an increase in the difference between the concentration of the main strong cation in milk (sodium) and the concentration of the main strong anions in milk (chloride and casein), thereby increasing the milk strong ion difference and pH (Kandeel, Megahed, Ebied, & Constable, ). An increased milk pH should cause more drug ionization and thus decreased diffusion across the blood–milk barrier, which was the opposite what we observed.…”

Clinical utility of urine specific gravity, electrical conductivity, and color as on‐farm methods for evaluating urine concentration in dairy cattle

“…Binary logistic regression was 34 Ninety-five percent confidence intervals were calculated for ROC, Se, Sp, +LR, and κ as described elsewhere. 35…”

“…Values for κ <0.2 indicate poor agreement, whereas 0.2 < κ < 0.4 indicates fair agreement, 0.4 < κ < 0.6 indicates moderate agreement, 0.6 < κ < 0.8 reflects good agreement, and κ >0.8 indicates excellent agreement . Ninety‐five percent confidence intervals were calculated for ROC, Se, Sp, +LR, and κ as described elsewhere …”