Comparing effects of bovine Streptococcus and Escherichia coli mastitis on impaired reproductive performance

摘要

In 2 epidemiological studies, we evaluated the effectof mastitis induced by gram-positive Streptococcus andgram-negative Escherichia coli on impaired reproductiveperformance in lactating Holstein cows. In the firststudy, 52,202 cows from 178 dairy farms throughoutIsrael were divided into groups based on infection beforefirst artificial insemination (AI) with Streptococcusor E. coli, 3 groups with elevated somatic cell count(SCC) without infection by those pathogens [low SCC(200–400) × 10~3 cell/mL; medium SCC (401–1,000) ×10~3 cell/mL; high SCC, >1,000 × 10~3 cell/mL], anduninfected controls. Pregnancy per first AI (P/1stAI)and pregnancy rate at 300 d in milk (PREG 300) wereanalyzed by the GLIMMIX procedure (SAS); numberof AI per pregnancy (AI/P), days open, and rest days(calving to first AI) were analyzed by the MIXEDprocedure (SAS Institute Inc., Cary, NC). Values ofP/1stAI were similarly low for Streptococcus and E. coli(27–28%) versus 42% in controls; PREG 300 was lowerfor Streptococcus (76%) than for E. coli (79%) versus88% for uninfected controls and a mean 83% for theelevated SCC groups. Days open and number of AI/Pwere higher than in controls and similar in Streptococcusand E. coli groups. The second study included 778cows on 6 dairy farms; the cows were infected beforefirst AI by Streptococcus or E. coli or uninfected. Resumptionof cyclicity was determined by an automatedactivity-monitoring system, and data were sorted bytime of infection before or after cyclicity resumed. TheStreptococcus group had lower P/1stAI before andafter cyclicity (26 and 27%, respectively) than the E.Coli group (31 and 34%, respectively) and uninfectedcontrols (42%). Notably, PREG 300 in the Streptococcusgroup before (73%) and after (67%) cyclicity wasmuch lower than for the E. coli group (85 and 93%,respectively) and the controls (95%). A marked risein day of cyclicity resumption (~80 d) was observedin cows that were infected early on. Number of AI/Pwas higher in the mastitic groups than in uninfectedcontrols. Uterine disease postpartum, although moreprevalent among Streptococcus cows, did not substantiallyalter the larger reduction in P/1stAI and PREG300 in Streptococcus versus E. coli cows. Thus, longtermStreptococcus-induced mastitis disrupted fertilitymore than short-term acute E. coli–induced mastitis,resulting in a much higher percentage of Streptococcuscows in late lactation that did not conceive due toreproduction failure.