Pigs subjected to beat stress decrease their feed intake that causes important economie losses. The objectives of the experiment were to determine the effects of dietaty live yeast supplementation (without or with Saccharomyces cerevisiae boulardii CNCM 1-1 079) on energy metabolism of finish ing boars (n= 1 0) at thermoneutrality or du ring beat stress challenge in respiration chamber. Nitrogen and energy balances were measured individually during three periods of 7, 7 and 6 days with ambient temperature of 22, 28 and 28 °C, respectively. Dietary live yeast supplementation increased dty matter intake from 2.29 to 2.65 kg/d, whereas beat stress decreased feed intake. These variations were associated with an increased number of meals when diet was supplemented (6.8 vs 5.5 meals/day) and a significantly increased eating speed of the control diet between periods 1, 2 and 3. Metabolisable energy intake was higher when diet was supplemented whereas total beat production was not affected. Finally, energy retention was higber with dietary live yeast supplementation but tended to decrease when ambient temperature increased.