Heat stress and cow factors affect bacteria shedding pattern from naturally infected mammary gland quarters in dairy cattle

Mastitis-causing pathogens are shed from infected mammary gland quarters and thus contribute to an increased risk of new intramammary infections. The objective the current study was investigate shedding characteristics various mastitis-causing associated animal-specific (somatic cell score parity) environmental (heat stress) factors. In a longitudinal study, udder were sampled consecutively on 5 dairy farms in Germany. To capture climatic factors, temperature-humidity index (THI) calculated. laboratory analysis, their counts milk samples determined. A generalized linear mixed model with gamma link used evaluate factors influencing pathogen-shedding characteristics. variables somatic count, pathogen, parity, THI had significant influence pathogen shedding. Staphylococci lower values than streptococci. infections higher first second lactation lactations. Exceeding threshold 60 resulted same day. This only caused by yeasts Streptococcus uberis. Possible mechanisms causing differences changes due influenced quantities, better growth conditions at temperatures, or altered immunological reactions. often remain speculative require further investigation. underlines contribution cows high regarding transmission mastitis within herd. Furthermore, it becomes clear that heat stress Germany influences health prevention measures useful.