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

Abstract

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.

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

“…The study reported here was part of a series of studies investigating the diagnosis of SCM and IMI in lactating dairy cattle. Additional results have been published elsewhere (Kandeel et al, 2017(Kandeel et al, , 2018b.…”

“…Finally, a CMT result of ≥trace had Se of 0.52 and Sp of 0.71 in early-lactation quarters and Se of 0.63 and Sp of 0.53 in late-lactation quarters (Godden et al, 2017). Because of the imperfect test Se and Sp of SCC and the CMT for diagnosing SCM and IMI, as well as the subjective nature of the CMT, there remains a need for new on-farm tests that provide a rapid, practical, inexpensive, and accurate method for diagnosing quarters with SCM and IMI to guide selective intramammary treatment at dry-off and freshening (Godden et al, 2017;Kandeel et al, 2018b).…”

Technological interventions and advances in the diagnosis of intramammary infections in animals with emphasis on bovine population—a review

“…2009; Kandeel et al. 2018a). Similarly, Somaticell ® has been found comparable to microscopic SCC and CMT (Ferronatto et al.…”

“…These markers are detected by various diagnostic methods, ranging from conventional observations, SCC, California mastitis test (CMT) (Kandeel et al. 2018a, 2018b; Rossi et al. 2018) to advanced polymerase chain reaction (PCR) (Mahmmod 2013), loop-mediated isothermal amplification (LAMP) (Bosward et al.…”

“…Initially, clinical observation, CMT, and white side test (WST) were the main field diagnostic tests, whereas SCC, culture and isolation were laboratory-based methods (Kandeel et al. 2018a, 2018b; Rossi et al. 2018).…”