An experimental comparison of methods for somatic cell count determination in milk of various species of mammals

Journal of Dairy Science

Ebeid

et al. 2019

Subclinical mastitis (SCM) and intramammary infection (IMI) increase esterase activity in the glandular secretions of dairy cattle. Our objective was to evaluate the clinical performance of 3 commercially available esterase tests for diagnosing SCM and IMI. Foremilk samples were collected from 380 quarters (96 cows) at dry-off and from 329 quarters (83 cows) within 4 to 7 d after calving. Quarter somatic cell count (SCC) was measured using the reference method (DeLaval cell counter; De Laval International AB, Tumba, Sweden) with SCM defined as SCC >200,000 cells/mL. Bacterial culture of foremilk samples was used to diagnose IMI based on the growth of ≥100 cfu/mL. The SCC was estimated using 3 PortaSCC tests (PortaCheck, Moorestown, NJ) from the measured esterase activity and the California Mastitis Test (CMT). Clinical performance was evaluated using logistic regression to determine the area under the receiver operating characteristic curve (AUC) and identify test sensitivity (Se) and specificity (Sp) at the optimal cut-point for diagnosing SCM and IMI. Test agreement was also evaluated using the kappa coefficient (κ) and weighted κ. The PortaSCC color test was the best-performing PortaSCC test for diagnosing SCM at dry-off (AUC = 0.90, Se = 0.91, Sp = 0.81, κ = 0.71) and at freshening (AUC = 0.86, Se = 0.74, Sp = 0.95, κ = 0.72), at an optimal cut-point of ≥250,000 cells/mL but required 45 min to produce a result. For comparison, the CMT required 2 min to produce a result and a CMT score of trace or higher was superior to the PortaSCC color test for diagnosing SCM at dry-off (AUC = 0.95, Se = 0.95, Sp = 0.86, κ = 0.81) and freshening (AUC = 0.88, Se = 0.79, Sp = 0.95, κ = 0.76). The PortaSCC quick test was the best-performing PortaSCC test for diagnosing IMI at dry-off (AUC = 0.81, Se = 0.81, Sp = 0.78 κ = 0.40) and required 5 min to produce a result, whereas the PortaSCC color test was the best performing PortaSCC test for diagnosing IMI at freshening (AUC = 0.80, Se = 0.75, Sp = 0.79 κ = 0.38). For comparison, the CMT was inferior to the PortaSCC quick test for diagnosing IMI at dry-off (AUC = 0.73, Se = 0.76, Sp = 0.60, κ = 0.20) but was equivalent to the PortaSCC color test at freshening (AUC = 0.79, Se = 0.58, Sp = 0.93, κ = 0.50). The PortaSCC color and quick tests and CMT were considered good tests for diagnosing SCM and IMI because clinically useful tests typically have an AUC >0.80 and κ >0.6. Based on the test sensitivity, cost, and analysis time, there does not appear to be a persuasive reason to select the PortaSCC tests over the traditional CMT for diagnosing SCM and IMI.

Section: Experimental Methodsmentioning

confidence: 99%

Evaluation of 3 esterase tests for the diagnosis of subclinical mastitis at dry-off and freshening in dairy cattle

Journal of Dairy Science

Ebeid

et al. 2019

“…The reference method for determining SCC in this study was the DeLaval cell counter (DCC; DeLaval International AB, Tumba, Sweden). The DCC method has been validated for bovine milk at 4 and 37°C against the Fossomatic (Foss, Hillerod, Denmark) and direct microscopic methods (Sarikaya and Bruckmaier, 2006;Malinowski et al, 2008;Kawai et al, 2013;Hanuš et al, 2014). The DCC is a portable automatic cell counter, with a reported measurement range of 10,000 to 4,000,000 cells/mL.…”

Section: Milk Analysis For Sccmentioning

confidence: 99%

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

Journal of Dairy Science

Ebeid

et al. 2019

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.

“…The manufacturer reported a coefficient of variation of 12% at 100,000 cells/mL, 8% at 400,000 cells/mL, and 7% at 1,000,000 cells/mL. In a separate study, the reference method was linear with the Fossomatic and direct microscopic tests when analyzing bovine milk samples at 0–6°C, but read approximately 12% lower than those 2 tests . Samples were measured with the DCC at the UIDRF within 2 hours of collection at room temperature (approximately 20°C; estimated range, 15–30°C) as recommended by the manufacturer.…”

Section: Methodsmentioning

confidence: 99%

“…In a separate study, the reference method was linear with the Fossomatic and direct microscopic tests when analyzing bovine milk samples at 0-6°C, but read approximately 12% lower than those 2 tests. 24 Samples were measured with the DCC at the UIDRF within 2 hours of collection at room temperature (approximately 20°C; estimated range, 15-30°C) as recommended by the manufacturer. Milk was drawn up using a piston into a single-use cassette that then was inserted into the DCC unit and analyzed.…”

Section: Somatic Cell Count Determinationmentioning

confidence: 99%

Evaluation and Comparison of 2 On‐Farm Tests for Estimating Somatic Cell Count in Quarter Milk Samples from Lactating Dairy Cattle

Veterinary Internal Medicne

Arnaout

et al. 2017

BackgroundThe somatic cell count (SCC) is commonly used to monitor udder health and diagnose subclinical intramammary infection (IMI) in dairy cattle.HypothesisThe Somaticell test (ST)2 and California mastitis test (CMT) are clinically useful cow‐side tests for diagnosing subclinical IMI.AnimalsOne hundred and eleven dairy cows at dry‐off and 92 cows within 4–7 days postcalving.MethodsQuarter foremilk samples were obtained and analyzed with a DeLaval cell counter (DCC, reference method),1 ST, and CMT. The ST was run in a simulated cow‐side manner using milk at 37°C instead of 0–8°C as recommended by the manufacturer. Test performance for diagnosing IMI (DCC SCC >200,000 cells/mL) was evaluated by calculating the area under the receiver operating characteristic curve (AUC) and the kappa coefficient (κ) at the optimal cut‐point for each test. The effect of milk/reagent temperature also was evaluated.ResultsCompared to the reference method, the ST run in a simulated cow‐side manner had an AUC = 0.68 and κ = 0.24 at dry‐off, and AUC = 0.74 and κ = 0.40 in fresh cows. The CMT performed much better than the ST in diagnosing subclinical IMI with AUC = 0.88 and κ = 0.77 at dry‐off, and AUC = 0.87 and κ = 0.76 in fresh cows. The measured ST value decreased with increasing temperature of the milk/reagent mixture.Conclusions/Clinical ImportanceThe ST is optimized for use on milk at 0–8°C and is therefore designed for on‐farm use on refrigerated milk samples. The ST is not suited for use as a cow‐side screening test for IMI because the milk temperature exceeds the recommended range for the test.