Jami, E., Department of Ruminant Sciences, Institute of Animal Science, Agricultural Research Organization, PO Box 6, Bet-Dagan 50250, Israel, Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat-Aviv 69978, Israel
Shabtay, A., Department of Ruminant Sciences, Institute of Animal Science, Agricultural Research Organization, PO Box 6, Bet-Dagan 50250, Israel
Nikbachat, M., Department of Ruminant Sciences, Institute of Animal Science, Agricultural Research Organization, PO Box 6, Bet-Dagan 50250, Israel
Yosef, E., Department of Ruminant Sciences, Institute of Animal Science, Agricultural Research Organization, PO Box 6, Bet-Dagan 50250, Israel
Miron, J., Department of Ruminant Sciences, Institute of Animal Science, Agricultural Research Organization, PO Box 6, Bet-Dagan 50250, Israel
Mizrahi, I., Department of Ruminant Sciences, Institute of Animal Science, Agricultural Research Organization, PO Box 6, Bet-Dagan 50250, Israel

This study characterizes the effects of concentrated pomegranate-peel extract (CPE) addition to the TMR at levels of 1, 2, or 4% on voluntary intake, in vivo digestibility, milk yield and composition, and profile of rumen bacterial and archaeal populations in lactating Holstein cows. Supplementation of CPE significantly affected the abundance of methanogenic archaea and specific ruminal bacterial species related to cellulolytic activities and soluble sugar and lactic acid fermentation, as revealed by real-time PCR quantification. Furthermore, CPE supplementation had a significant dose-dependent effect on the whole ruminal bacterial community, as determined by automated ribosomal intergenic spacer analysis. These changes were accompanied by a significant increase in digestibility of dry matter, crude protein, and neutral detergent fiber, as well as milk and energy-corrected milk yields in cows fed the 4% CPE supplement. These results suggest that CPE supplementation significantly affects the rumen bacterial communities, which in turn may be related to a beneficial effect on dairy cow performance. © 2012 American Dairy Science Association.