Aim of study: The goal of this study was to investigate the effects of encapsulation of Lactobacillus acidophilus (LA) and Spirulina platensis (SP) on the growth performance, blood metabolites, intestinal morphology, and gut microflora of broilers under heat stress. Area of study: The work was performed at the University of Jiroft, Iran. Material and methods: A total of 240, one-day-old Ross 308 male broilers were allocated to six treatments, with four replicates (10 birds each) per treatment. The six dietary groups were as follows: (1) corn-soybean as control diet (Control), (2) control diet including 0.02% LA (LA), (3) control diet including 1% SP (SP), (4) control diet including 0.02% LA + 1% SP (LA+SP), (5) control diet including 0.02% LA encapsulated (encapsulated LA), and (6) control diet including 0.02% encapsulated LA and 1% encapsulated SP (encapsulated LA+SP). To induce chronic heat stress, birds were exposed to an ambient temperature of 34 ± 2 °C for 8 h daily (from 10:00 am until 18:00 pm) from 25 to 42 d of age. At the end of the trial, two chicks/pen were randomly selected, and the performance, blood metabolites, jejunal morphology, and ileal microbial populations were evaluated. Main results: All experimental groups had higher feed intake (FI), body weight gain (BWG) and lower feed conversion ratio (FCR), compared to the control. The highest FI and BWG were seen in birds fed by LA+SP and encapsulated LA+SP (P˂0.05). The lowest cholesterol and the highest activity of glutathione peroxidase enzyme in blood serum were seen in the LA+SP treatment (P˂0.05). Dietary treatments with LA, SP or both significantly increased villus height (VH), crypt depth (CD) and villus height/crypt depth ratio and decreased villus width compared to the control (P˂0.05). The effect of dietary treatments on ileal microbial community was significant since Lactobacillus spp. counts increased and Escherichia coli counts decreased in all dietary treatments compared to the control group (P˂0.05). Research highlights: In general, adding LA, SP, and a combination of both, encapsulated or not in broiler’s feeds alleviated the negative effects of heat stress on growth performance, and ameliorate blood metabolites, jejunal morphology and ileal microbial populations of broilers.
