Performance and nutrient utilization of rats fed various selenium levels under heat stress-and thermo-neutral conditions

Seventy-two male Wistar rats of 4 weeks age and 67.6±1.53 g BW were randomly assigned to six groups of twelve rats in each to investigate the effect of three dietary selenium (Se) levels on the performance and nutrient utilization of rats fed on a purified diet under heat stress (HS) and thermoneutral (TN) condition. The groups under TN conditions were CON, Se300_C, and Se450_C and groups under HS conditions were CON_HS, Se300_HS, and Se450_HS. The total experimental duration was 42 d. The TN groups were reared at thermoneutral conditions throughout the experimental period. On the other hand, the HS groups were reared in the thermoneutral condition for an initial 28 d, but during the next 14 d, they were exposed to heat stress for 6 h/d in a psychrometric chamber. A metabolism trial was conducted during the last six days of the experiment. The temperature-humidity index was 57.3±0.22 and 77.0±0.11 in the TN and HS groups, respectively. The DMI was lower (P<0.05) in CON_HS compared to CON and was similar among the HS and TN groups at higher Se levels; however, it was lower in CON_HS compared to Se300_HS and Se450_HS. The ADG during the 3rd to 6th week were lower in Se300_C and Se450_C than in the CON group; however, BW gain and ADG were similar among CON_HS, Se300_HS, and Se450_HS. There was no difference (P>0.05) in nutrient intake, digestibility and nitrogen balance of rats among the treatment groups, Se levels, and environmental conditions. It was deduced that dietary selenium at 291 to 460 ppb is beneficial for preventing the deleterious effect of heat stress on DMI and lowering the body, tail and eye temperatures.