The addition of Na‐lactate (50–150 mmol/1) to media with glucose had only marginal effect on the growth of rumen lactate‐producing bacteria at pH between 6.5 and 5.8.Butyrivibrio fibrisolvenswas somewhat more sensitive to external lactate thanStreptococcus bovis, Lactobacillus fermentumandSelenomonas ruminantium.It can be concluded that rumen lactate producers, which proliferate at the onset of rumen lactic acidosis, are not influenced by the lactate accumulation, except some non‐specific osmotic effects.