The effect of intramammary infection in early lactation with non-aureus staphylococci in general and Staphylococcus chromogenes specifically on quarter milk somatic cell count and quarter milk yield

Abstract

This longitudinal study aimed to evaluate the impact of subclinical intramammary infection (IMI) with nonaureus staphylococcal (NAS) species in the first 18 d in milk (DIM) on the quarter milk somatic cell count (qSCC) and quarter milk yield (qMY) during the first 4 mo of lactation in Holstein Friesian heifers. Quarter milk samples were collected from 82 heifers from 1 to 4 DIM until 130 DIM on a biweekly (14 d) basis for determination of the qSCC; qMY data were available through the automatic milking systems. The quarter samples collected on the first (1-4 DIM) and second (15-18 DIM) sampling days were used for bacteriological culturing to determine the IMI status. In this study, 324 quarters from 82 heifers were enrolled, of which 68 were NAS-infected at the first sampling day. Only 16 (23.5%) of these quarters were still NAS-infected at the second sampling day, demonstrating the high spontaneous cure rate of these infections shortly after calving; 9 of these 16 cases were infected with the same NAS species. Interestingly, none of the NAS-infected quarters at the first sampling day acquired a new infection with a major pathogen at the second sampling day, whereas 2.3% of the noninfected quarters did. All 102 isolates phenotypically identified as NAS were further identified to the species level. Staphylococcus chromogenes was the most prevalent species on the first (29.4% of all NAS) and second (52.9%) sampling days. Quarters infected with Staph. chromogenes at the first sampling day had a significantly higher qSCC in later lactation than noninfected quarters, whereas this was not true for quarters infected with all other NAS species (i.e., as a group of species). The average daily qMY in the first 4 mo of lactation did not differ between noninfected quarters and quarters infected with Staph. chromogenes or all other NAS species at the first sampling day. Persistently NAS species-infected quarters in the first 18 DIM (i.e., infected with the same NAS species on the first and second sampling days) had the highest qSCC later in lactation, followed by quarters with a new NAS IMI (i.e., noninfected at the first sampling day and infected with NAS at the second sampling day). The qSCC from transiently NAS species-infected quarters (i.e., not infected with the same NAS species at the second sampling day) was not significantly higher in later lactation compared with that in noninfected quarters. The IMI status of quarters in the first 18 DIM, combining culture results at 1 to 4 and 15 to 18 DIM (new, persistent, and transient IMI), was not significantly associated with daily qMY in the first 4 mo after calving. In general, NAS should be considered minor pathogens with no adverse effect on daily qMY in quarters of heifers infected in the first 18 DIM and with a high spontaneous cure rate. Staphylococcus chromogenes was the most prevalent species, causing an increase in qSCC comparable to the level of quarters infected with a major pathogen; Staph. chromogenes caused most infections that persisted through at least the fir...

Longitudinal study on the effects of intramammary infection with non-aureus staphylococci on udder health and milk production in dairy heifers

“…Part of the discrepancies among different studies can be attributed partly to the great variation in study design, such as length of the follow-up period, number of herds and animals, definition of IMI, and selection of included animals (e.g., heifers vs. multiparous cows, animals at the start of lactation vs. any lactation stage) but also the identification methods (i.e., phenotypic vs. genotypic methods). In our previous work, we documented that NAS IMI between 1 and 4 DIM and in the first 18 DIM resulted in a higher qSCC during the first 4 mo of lactation, but had no effect on qMY (Valckenier et al, 2019(Valckenier et al, , 2020. However, we observed a difference between S. chromogenes and other NAS species in terms of occurrence, persistence, and effect of IMI in the first 18 d after calving on later qSCC and qMY.…”

“…Some studies found no significant differences in quarter milk SCC (qSCC) between different NAS species (Hogan et al, 1987;Bexiga et al, 2014), whereas others noted that important species differences exist (Supré et al, 2011;Fry et al, 2014). Moreover, in our previous study, we concluded that IMI with S. chromogenes starting in the first 18 DIM resulted in a significantly higher qSCC during the first 130 DIM, whereas IMI with the group of other NAS species had no effect on qSCC (Valckenier et al, 2020). Some NAS species, such as Staphylococcus chromogenes, S. simulans, and S. xylosus, are called species "more relevant for udder health" as they are able to increase the qSCC to a level comparable to that of S. aureus (Supré et al, 2011), as substantiated by Fry et al (2014).…”

“…All bacteria not belonging to the group of NAS or to one of the abovementioned major pathogens were considered "other" bacteria. A sample yielding a major pathogen and NAS or other bacteria was classified as culture-positive for the major pathogen, whereas a sample yielding 2 different major pathogens or 2 different minor pathogens was considered as culture-positive for the pathogen with the highest count (cfu/mL; Valckenier et al, 2019Valckenier et al, , 2020.…”

“…The effect of NAS infections on milk yield (MY) is even more debated, although most recent research con-siders NAS minor pathogens with little to no effect on the quarter MY (qMY; Tomazi et al, 2015;Heikkilä et al, 2018;Valckenier et al, 2019Valckenier et al, , 2020. If IMI with all of the different NAS species have a negative or no effect on MY, the focus should remain on prevention of infection with these pathogens because NAS IMI lead to an elevated SCC and have been previously identified as a risk factor for developing IMI with S. aureus (Reyher et al, 2012a).…”

Randomized controlled field trial comparing quarter and cow level selective dry cow treatment using the California Mastitis Test

“…together and treated them as a single group. While there is an increasing body of evidence to suggest that all NAS are not equal (Valckenier et al, 2020;Wuytack et al, 2020), we took this approach to facilitate comparison with earlier research in the area. A more detailed analysis of the outcomes and potential roles of the individual NAS spp.…”