Bach, S. J., Cook, S. R., Wang, Y., Stanford, K., Johnson, R. P. and McAllister, T. A. 2012. Short Communication: Escherichia coli O157 bacteriophages: lytic activity and effects on fermentation in ruminal batch culture. Can. J. Anim. Sci. 92: 545-550. The effect of three lytic Escherichia coli O157, rV5, wV8 and wV11 on in vitro pH, gas production and dry matter disappearance in bovine ruminal cultures were assessed. None of the bacteriophages altered any of the measured parameters in ruminal fluid from concentrate or forage-fed animals. All bacteriophages were able to persist in ruminal fluid from forage and concentrate-fed cattle over a 24-h period; however, lytic activity against E. coli O157:H7 in ruminal batch cultures was not evident.