An 8-week feeding experiment was designed to examine the influences of single or/and double strains of probiotic compared to antibiotic colistin on growth, hematological variables, blood serum metabolites and caecal fermentation in post-weaning rabbits exposed to heat stress conditions. A total of one hundred (35-day-old; average initial body weights 694 ± 7.33) New Zealand White rabbits were distributed into five groups. The experimental groups were the basal diet (control), or basal diet fortified with 120 mg colistin (COL); 5 Â 10 6 cfu Clostridium butyricum (CB); 2 Â 10 8 cfu Enterococcus faecium NCIMB 11181 (EF); or 2.5 Â 10 6 cfu C. butyricum þ 1 Â 10 8 cfu E. faecium/kg diet (CB þ EF). The results demonstrated that both the EF and CB þ EF treatments enhanced (p < .05) final body weight and overall feed conversion ratio compared to control and COL treatment. The carcase yield percentage and relative organs weight were insignificantly affected in all treated groups. The COL treatment increased (p < .05) mean corpuscular volume and albumin/globulin ratio compared to the control group. Compared to the control, all probiotic and COL groups decreased (p < .05) serum total triglycerides and very low-density lipoprotein. The concentrations of Serum total protein, globulin, highdensity lipoprotein, complement component 3, and lysozyme activity were higher (p < .05) in probiotic groups than those in the control group. Probiotic application improved the caecal total volatile fatty acids, propionate concentrations, and intestinal histomorphometry parameters. In conclusion, EF and CB þ EF probiotic supplements could be used as alternatives to antibiotic colistin to enhance the growth and health of weaned rabbits under heat stress conditions. HIGHLIGHTSTwo strains of probiotics as alternatives to antibiotics were studied in rabbits under heat stress conditions. Supplemental EF and CB þ EF probiotic enhanced rabbit growth and feed utilisation. Probiotic application improved biochemical and immunological indicators. The application of the tested probiotics improved the caecal volatile fatty acids production and the intestinal histomorphometry parameters. EF and CB þ EF probiotic supplements could be used as an alternative to antibiotics to promote the growth of rabbits under heat stress conditions.

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