Effects of housing system and dietary mannan oligosaccharides on broiler performance, corticosterone response to transportation, and selected caecal bacterial populations under humid tropical conditions

Abstract This study examined the effects of housing system and dietary mannan oligosaccharides (MOS) on growth performance, serum corticosterone (CORT), and selected caecal bacterial populations in broiler chickens exposed to road transportation under humid tropical conditions. A total of 440 one-day-old male Cobb 500 chicks were assigned to a 2 × 2 factorial arrangement involving naturally ventilated (NVH) or mechanically ventilated housing (MVH) and a control diet or the same diet supplemented with MOS at 2.0 g/kg. On day 42, separate groups of birds were sampled before transport or after 4 h of road transportation. Broilers reared in MVH had greater final body weight and better feed conversion than those reared in NVH. MOS supplementation also improved final body weight and feed conversion ratio. Transportation increased serum CORT concentrations, while birds reared in MVH and those fed MOS had lower overall CORT concentrations. No significant interactions were detected among housing system, diet, and sampling time for CORT. Housing system also affected selected caecal bacterial populations, with lower Clostridium spp. and higher Lactobacillus spp. counts in MVH birds. MOS supplementation and transportation did not significantly affect the measured bacterial populations. These findings indicate that housing environment and MOS supplementation mainly influenced broiler performance and physiological status independently under humid tropical conditions, while short-term transportation increased CORT without measurable changes in the selected caecal bacterial populations.