Differential somatic cell count as an additional indicator for intramammary infections in dairy cows

Abstract

Mastitis, often caused by intramammary infection (IMI), is a significant problem in dairy farming globally. Somatic cell count (SCC) is widely used as a parameter for screening IMI in cows that are then treated or culled. We investigated the potential of a new parameter, differential SCC (DSCC), to detect IMI at cow level when SCC is already known. We achieved this using bacterial culture (BC) and PCR to detect 4 categories of pathogens (major, minor, other, and any) in 2 Danish dairy herds. Quarter milk samples were collected from monthly dairy herd improvement samplings over 1 yr and analyzed with BC, whereas cowlevel dairy herd improvement samples were analyzed using PCR. Days in milk, parity, and IMI status had a significant effect on DSCC. Using DSCC in addition to SCC significantly improved the indication of IMI compared with using only SCC in the any pathogen category in both herds as well as the minor pathogens category in herd 2 when BC was used for detection. When PCR was used to detect IMI, the use of DSCC in addition to SCC was significant for the other pathogens category in herd 1 and the minor pathogens category in herd 2. Thus, our data revealed that DSCC can add significant information describing IMI status even when SCC is already known; however, this depends on the causative pathogen. Future studies may address how to use DSCC in practice as well as consider the availability of temporal data to potentially gain insight into the course of infection.

Factors Affecting the Patterns of Total Amount and Proportions of Leukocytes in Bovine Milk

“…The trend analysis showed a decrease of DSCC with increasing DIM when SCC was ≤50,000 cells/mL, but no significant trends were observed at higher SCC levels ( Table 7 ). These data did not agree with the results of studies applying flow-cytometry [ 29 ], neither with the ones from a recent study applying the same instrument as in this study [ 14 ]. However, in the latter case, data were not ranked by SCC levels.…”

“…The availability of a sample size larger than the ones reported even in recent studies on DSCC [ 14 , 15 , 16 , 24 , 28 ] and the period of time during which samples were collected allows to investigate the pattern of cell types during the course of the whole lactation. The statistical model applied for evaluating factors affecting DSCC variability in a healthy subset showed that, among random factors, the herd has a very low influence, while all fixed factors considered, as well as their interactions showed a statistically significant influence ( Table 2 ).…”

“…To the best of our knowledge, studies on leukocyte patterns throughout lactation and parities are scarce and the few available are focused on specific aspects, such as the association with SCC or the values at the end of lactation [ 14 , 15 , 16 , 17 ]. Moreover, studies on the variability of the total amount of different leukocytes in milk are scarcer [ 4 , 18 ], and based on a very small sample size.…”

Differential Somatic Cell Count: Value for Udder Health Management

“…Kirkeby et al (26) found a significant association between F-DSCC and both DIM and lactation number. F-DSCC generally decreased over the course of the lactation, and the relationship between F-DSCC and lactation number was found ambiguous (26).…”

Combining total and differential somatic cell count to screen for mastitis

“…Given that there is no true gold standard for the diagnosis of mastitis or IMI (Adkins & Middleton, 2018), we focused on inflammation rather than infection and considered SCC as a gold standard to perform ROC analysis, as previously done by Zecconi et al (2019). Investigations on DSCC for the identification of IMI have been recently conducted by Kirkeby et al (2019) and Schwarz et al (2019), who concluded that DSCC can add significant information on IMI and that obtained results justify further studies on the combined use of DSCC and SCC to detect IMI.…”