Growth performance such as body weight gain and feed
intake decreases under heat conditions (Cheng et al., 1997).
This was confirmed in this study (Fig. 1), indicating that heat
stress was successfully induced. Moreover, the feed efficiency
was also decreased by heat exposure (Fig. 1) as previously
reported (Cheng et al., 1997). In addition, the feed
efficiency in the 24PF group was also significantly lower
than that in the control group (Fig 4). Therefore, the reduction
of feed intake is thought to be one of the causes for
the decrease of the feed efficiency by heat exposure. Feed
efficiency in the HS group was significantly lower than that
in the 24PF group (Fig. 4), suggesting that heat stress affect
biofunctions in broiler chickens, resulting in feed efficiency
reduction