Accuracy of the detection of intramammary infection using quarter somatic cell count when taking parity and stage of lactation of the dairy cow into account

Abstract

-The aim of this study was to determine if taking parity and stage of lactation of the dairy cow into account could improve the sensitivity (Se) and specificity (Sp) of a SCC-test to detect quarter intramammary infection (IMI). A total of 27 315 quarter milk samples were collected from 277 Holstein cows from one experimental herd from 1980 to 1994. Two analyses were carried out. In the first analysis (MIN+MAJ analysis), quarter samples showing at least a single isolation of a minor or a major pathogen were considered as infected. In the second analysis (MAJ analysis), only quarter samples showing at least a single isolation of a major pathogen were considered as infected. The SCC threshold value above which a quarter was defined positive was the one which maximised the Youden index (YI). Se, Sp and YI were calculated on (1) the whole study sample (herd level), and (2) 6 subsamples defined according to parity (primiparous versus multiparous) and stage of lactation (0 to 60 days, 61 to 120 days and 120 to 400 days). Se, Sp and YI were also recalculated at the herd level on the basis of Se and Sp obtained for each subsample. The SCC threshold selected on the whole study sample was 265 000 cells·mL -1 in the MIN+MAJ analysis and 420 000 cells·mL -1 in the MAJ analysis. At these thresholds, the Se and Sp values were 71.2% and 75.8% respectively (MIN+MAJ analysis) and 82.9% and 83.6% respectively (MAJ analysis). For both analyses, the SCC thresholds, Se and Sp varied according to parity and stage of lactation. Finally, the results showed that taking the cow characteristics into account had a very limited impact on the accuracy of IMI detection.

Feasibility of utilising an infrared-thermographic technique for early detection of subclinical mastitis in dairy camels (Camelus dromedarius)

“…Despite the fact that intramammary infection upon microbiological culturing is associated with increased SCC and CMT score, the true health status of any udder relies essentially on the presence of microbial pathogens (Younan et al 2001; Wahba et al 2005; Saleh et al 2013). In dairy cows, several authors report that the sensitivity and specificity to detect positive intramammary infection is 46–84 and 82–98%, respectively, for CMT score, and 61–83 and 58–84%, respectively, for SCC (Djabri et al 2002; Wahba et al 2005; Polat et al 2010). Furthermore, controlled environmental conditions are also required when using IRT (McCafferty et al 2011).…”

Temporal Trends in Bulk Tank Somatic Cell Count and Total Bacterial Count in Irish Dairy Herds During the Past Decade

“…A highly season pattern in SCC during the year (Figure 3) is a function of the seasonal calving system of milk production in Ireland (Figure 1) and changes in SCC across lactation. The SCC tends to be highest in very early and late lactation and at a minimum in midlactation (Schepers et al, 1997;Djabri et al, 2002). Although the mean SCC increased from May, the rate of increase intensified from September onward.…”

Risk factors for new intramammary infections during the dry period in untreated dairy cows from herds using selective dry cow therapy

“…On the other hand, the microbiological procedure results could also have been re-interpreted in the light of quarter milk SCCs, if available. However, the sensitivity and specificity of a test based on the quarter SCC for a threshold of 100 000 cell per ml are respectively from 65% to 92% and from 29% to 83% (Lindströ m et al, 1981;Arendt et al, 1997), and is even worse at the end or at the beginning of lactation (Djabri et al, 2002). Therefore, SCC determination at the quarter level was not implemented in this study.…”