The study used 96 day-old Cobb 500 chicks, weighed individually and housed in an experimental hall with 320C constant temperature and 23 h light regimen. During the starter stage (1-14 days), all chicks received a conventional diet formulation with sodium monensin (50 g/kg premix). During the growth stage (14-35 days), when the actual feeding trial started, the chicks were weighed, assigned to three groups (32 chicks/group) and housed in the same experimental hall. Throughout the experimental period, the temperature was maintained at 32sup0/supC, humidity 36%, 23 h light regimen. Like in the starter stage, the chicks had free access to the water and feed. Compared to the diet formulation for the control group (C), conventional formulation, with monensin in the premix, the formulations for the experimental groups included 2% dry oregano (E1), or 2% rosehip powder (E2), but no monensin in the premix. Throughout the experimental period were monitored the bodyweight and the intake. At the end of the feeding trial, 6 chicks from each group were slaughtered in order to make measurements of the relative weight of carcass cuts and internal organs of broilers. Samples of intestinal content were collected for bacteriological assessment (determination of the Enterobacteriaceae, E. coli and Lactic acid bacteria). Throughout the entire experimental period (14-35 days), the average daily feed intake was significantly higher in group C than in groups E1 and E2, but the average daily weight gain and the feed conversion ratio were not different among the three groups. The dietary phytoadditives given the broiler chicks reared under heat stress (32sup0/supC) had a favourable action in maintaining the health of the intestinal tract, by preserving the balance of the populations of microorganisms colonizing the intestine. Throughout the experimental weeks under heat stress no mortalities were recorded in any of the three groups.
Criste et al. (Fri,) studied this question.