Dynamics of somatic cell count (SCC) and differential SCC during and following intramammary infections

Abstract

Somatic cell count is frequently used as an indicator of intramammary infections (IMI) in dairy cattle worldwide. The newly introduced differential SCC (DSCC) can potentially contribute to detection of IMI. The purpose of this study was to investigate the dynamics of SCC and DSCC after IMI. We used a data set with monthly samples from 2 Danish dairy herds through 1 yr, using bacterial culture to identify IMI. The dynamics of SCC and DSCC with regard to IMI were assessed at quarter level following new IMI with each of 3 defined pathogen groups, major, minor, or "other" pathogens, using general additive models. Both SCC and DSCC increased after IMI, with a more pronounced increase if major or other pathogens were detected compared with minor pathogens. We found that DSCC increased after IMI with other pathogens in both herds and, in herd 2, after IMI caused by major and minor pathogens. We also estimated the duration of increased SCC and DSCC when they exceeded a threshold, done separately for each pathogen group. Major pathogens had the longest-lasting effect in both herds for both SCC and DSCC. We conclude that the magnitude and duration of response of SCC and DSCC to IMI differs between herds and causative pathogens.

Association between differential somatic cell count and California Mastitis Test results in Holstein cattle

“…This discrepancy probably resulted from the distinct differential cell counts between the 2 cases. Studies have reported DSCC values to be higher in cows with IMI caused by major pathogens compared with those in cows without IMI or with IMI caused by minor pathogens ( Schwarz et al, 2020b ; Kirkeby et al, 2021 ), consistent with the current observation. If the CMT was used for guiding an SDCT program, for instance, antibiotics may be allocated to quarters without IMI.…”

“…Recently, a new method has been developed to efficiently determine differential cell counts in milk ( Damm et al, 2017 ), which measures the combined proportions of PMN and lymphocytes, namely differential SCC ( DSCC ); macrophage proportions ( MAC ) can be calculated by the formula 100 − DSCC. Studies have reported that DSCC also varies between stages of mastitis ( Kirkeby et al, 2021 ).…”

Transmission Dynamics of Corynebacterium spp. Within Two Danish Dairy Cattle Herds

“…The samples were then preserved using 0.5% boric acid, and bacteriological analysis took place within 48 h of collection. Bacteriological analysis was conducted as explained in Kirkeby et al ( 16 ). Briefly, identification was performed using bacteriological culture (BC) where a sterile glass loop was used to streak 10 μLof each sample to a quarter of a blood agar plate with 0.1% esculine, corresponding to one plate per cow.…”

Udder Pathophysiology and Public Health

“…Milk somatic cell counts are usually used as diagnostic tool. The mean somatic cell count in healthy buffaloes is 3.64 x 10 5 , while in cattle it is 3.40 x 10 5 , while in mastic animals these values are 62.69 and 41.34 x 10 5 , respectively (Shah et al 2017;Kirkeby et al 2021;Leitner et al 2000a;Pillai et al 2001;Moroni et al 2005;Dhakal 2006;Lindmark-Mansson et al 2006;Suriyasathaporna et al 2006Piepers et al 2009Fakhar-uz-Zaman et al 2009). Some pathogens release metabolic by-products, or toxins when they enter and multiply in the mammary tissue.…”