Subclinical mastitis (SCM) is an asymptomatic worldwide udder infection that
results in substantial losses to the dairy industry. Our main objective was to
evaluate and compare the clinical performance of 4 commercially available
screening tests for diagnosing SCM. Foremilk samples were collected from 428
quarters of 107 apparently healthy lactating cows and buffaloes from El-Menofia
governorate from 2020 to 2022. Quarter somatic cell count (SCC) was estimated
using the FOSS-BacSomatic®
counter and the California Mastitis Test (CMT),
with SCM defined as SCC > 200,000 cells/mL. Milk pH was measured cow-side
using an AD11®
pH-meter and BOVIVET®
indicator paper. Bacterial cultures of
foremilk samples were used to diagnose SCM as a reference method based on the
isolation of the causative pathogens. The tests’ performance was evaluated by
calculating test sensitivity (Se), specificity (Sp), and accuracy at the optimal-cutpoint for each test. FOSS-BacSomatic®
counter was the best-performing test for
diagnosing SCM (Se = 0.967, Sp = 0.943, accuracy = 0.957) at an optimal-cutpoint of >200,000 cells/mL. For comparison, CMT is the second best-performing
test at an optimal-cut-point of a non-negative score (Se = 0.892, Sp = 0.878,
accuracy = 0.887). The test performance of the AD11® pH-meter and BOVIVET®
indicator paper was fair, however, the AD11® pH-meter performed better than the
BOVIVET®
indicator paper with Se = 0.807, Sp = 0.845, and accuracy = 0.822.
We concluded that the FOSS-BacSomatic®
counter and CMT are considered
good tests for diagnosing SCM. On the other hand, milk pH doesn’t provide a
clinically useful method for diagnosing SCM. However, based on cost,
availability and analysis time, there doesn't seem to be a persuasive reason to
select the FOSS-BacSomatic®
counter over the traditional CMT to diagnose
SCM.