Carbon dioxide production, energy expenditure and 14CO2 recovery in sows given hourly meals, each of one-eighth of daily intake. After 2 hourly feedings, intravenous NaH14CO3 solutions were infused for 4 h with hourly feedings maintained. CO2 production and energy expenditure were calculated each minute and breath 14CO2 was collected in 30 min periods. Data are means of n = 5 sows at each time point. : Energy expenditure. : CO2 production. ●: 14CO2 recovery.