Effect of fiber content of roughage on energy cost of eating and rumination in Holstein cows

•Energy costs of chewing in cows are able to be obtained by using a multiple linear regression model.•Energy costs of total chewing per dry matter intake and that per metabolizable energy intake are higher for cows fed high fiber roughage than cows fed low fiber roughage.•Energy cost of total chewing relates to NDF content of roughage.•NDF content of roughage relates to loss of metabolizable energy available for production.