Postcalving udder health and productivity in cows approaching dry-off with intramammary infections caused by non-aureus Staphylococcus, Aerococcus, Enterococcus, Lactococcus, and Streptococcus species

S. M. Rowe, S. M. Godden, E. Royster, J. Timmerman, M. Boyle

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


The objective of this prospective cohort study was to explore associations between intramammary infection (IMI) in late-lactation cows and postcalving udder health and productivity. Cows (n = 2,763) from 74 US dairy herds were recruited as part of a previously published cross-sectional study of bedding management and IMI in late-lactation cows. Each herd was visited twice for sampling. At each visit, aseptic quarter milk samples were collected from 20 cows approaching dry-off (>180 d pregnant), which were cultured using standard bacteriological methods and MALDI-TOF for identification of isolates. Quarter-level culture results were used to establish cow-level IMI status at enrollment. Cows were followed from enrollment until 120 d in milk (DIM) in the subsequent lactation. Herd records were used to establish whether subjects experienced clinical mastitis or removal from the herd, and DHIA test-day data were used to record subclinical mastitis events (somatic cell count >200,000 cells/mL) and milk yield (kg/d) during the follow-up period. Cox regression and generalized estimating equations were used to evaluate the associations between IMI and the outcome of interest. The presence of late-lactation IMI caused by major pathogens was positively associated with postcalving clinical mastitis [hazard ratio = 1.5, 95% confidence interval (CI): 1.2, 2.0] and subclinical mastitis (risk ratio = 1.5, 95% CI: 1.3, 1.9). Species within the non-aureus Staphylococcus (NAS) group varied in their associations with postcalving udder health, with some species being associated with increases in clinical and subclinical mastitis in the subsequent lactation. Late-lactation IMI caused by Streptococcus and Streptococcus (Strep)-like organisms, other than Aerococcus spp. (i.e., Enterococcus, Lactococcus, and Streptococcus spp.) were associated with increases in postcalving clinical and subclinical mastitis. Test-day milk yield from 1 to 120 DIM was lower (−0.9 kg, 95% CI: −1.6, −0.3) in late-lactation cows with any IMI compared with cows without IMI. No associations were detected between IMI in late lactation and risk for postcalving removal from the herd within the first 120 DIM. Effect estimates reported in this study may be less than the underlying quarter-level effect size for IMI at dry-off and postcalving clinical and subclinical mastitis, because of the use of late-lactation IMI as a proxy for IMI at dry-off and the use of cow-level exposure and outcome measurements. Furthermore, the large number of models run in this study (n = 94) increases the chance of identifying chance associations. Therefore, confirmatory studies should be conducted. We conclude that IMI in late lactation may increase risk of clinical and subclinical mastitis in the subsequent lactation. The relationship between IMI and postcalving health and productivity is likely to vary among pathogens, with Staphylococcus aureus, Streptococcus spp., Enterococcus spp., and Lactococcus spp. being the most important pathogens identified in the current study.

Original languageEnglish (US)
Pages (from-to)6061-6079
Number of pages19
JournalJournal of Dairy Science
Issue number5
StatePublished - May 1 2021

Bibliographical note

Funding Information:
We thank the Zoetis Quality Milk Specialist and Dairy Technical Services teams (Julio Alcantar, Michele Barrett, Karthryn Browning, Ruben Gonzalez, Samuel Herrera, Bernard Kwaku, Shawn Hull, Doris Ledwith, John Lee, Francisco Rivas, and Bill Sullivan), who conducted the fieldwork in herds located outside of Minnesota. We also thank DVM students, as well as Samuel Basquin and Edouard Cotton, from the University of Minnesota. S. M. Rowe was involved in study conceptualization, fieldwork, laboratory work, data management, analysis, and manuscript preparation; S. M. Godden was involved in study conceptualization, fieldwork, and manuscript editing; J. Timmerman was involved in laboratory work and manuscript editing; and E. Royster and M. Boyle were involved in manuscript editing. This study was funded by Zoetis (Parsippany, NJ). M. Boyle is an employee of Zoetis; he was involved in the study conceptualization and review of the manuscript but was not involved with any analyses of data. No other authors have competing interests to declare.

Publisher Copyright:
© 2021 American Dairy Science Association


  • Streptococcus and Strep-like organisms
  • intramammary infection
  • mastitis
  • postcalving health

PubMed: MeSH publication types

  • Journal Article


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