Energy requirement for eating in cattle.

We determined the energy requirement for the activity associated with eating in an experiment with four adult Hinterwälder steers weighing 640+/-25 kg BW (mean+/-SD), using indirect calorimetry in respiration chambers. Heat production was measured during 3 h with and 3 h without ad libitum access to wheat straw, and the energy cost of eating was calculated as the difference, which was on average 27+/-13 J/(min x kg BW) (mean+/-SD). Straw intake, the time spent for eating, and the number of jaw movements were recorded. Values for the energy cost of eating reported in the literature are similar to those in this study, and values for ruminating amount to approximately 27% of those for eating. The energy cost of eating (literature values) varies greatly between feeds and feed treatments, when related to the amount of feed ingested, but it was relatively constant when related to time spent eating and was similar for cattle, sheep, and horses, when related to BW or metabolic BW (35 J/[min x kg BW] or 124 J/ [min x kg BW.75]). Calculations indicated that in high-quality roughage 10% of the ME and in untreated straw approximately 30% of the ME provided by the feed are used for eating and ruminating. This might be the main reason for the lower efficiency of ME utilization in roughages. The energy requirement for eating and ruminating should therefore be considered as a distinct proportion of the total ME requirement.