Enterococcus faecium and Clostridium butyricum combined with selenium as alternatives to the antibiotic colistin: Impacts on growth, cecal fermentation, and immune function in rabbits raised under hot environmental conditions

Mohamed El-Kholy ¹ Samar S Bassiony ¹ Adham A Al-Sagheer ² Mahmoud M Alagawany ^3,4* Mohammed Ghonime ⁵ Eman A Elwakeel ⁶ Antonia Lestingi ⁷ Ahmed Elolimy ⁸ Mahmoud Madkour ⁹ Mahmoud M. Azzam ¹⁰ Shaaban S Elnesr ¹¹

• ¹ Poultry Department, Faculty of Agriculture, Zagazig University, Zagazig, Al Sharqia, Egypt
• ² Department of Animal Production, Faculty of Agriculture, Zagazig University, Zagazig, Al Sharqia, Egypt
• ³ Zagazig University, Zagazig, Egypt
• ⁴ Poultry Department, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt, Zagazig, Al Sharqia, Egypt
• ⁵ Department of Animal and Poultry Production, Faculty of Agriculture and Natural Resources, Aswan University, Aswan, Aswan, Egypt
• ⁶ Department of Animal and Fish Production, Faculty of Agriculture, Alexandria University, Alexandria, Alexandria, Egypt
• ⁷ Department of Veterinary Medicine, University of Bari Aldo Moro, Valenzano, Italy
• ⁸ College of Agriculture and Veterinary Medicine, United Arab Emirates University, AlAin, Abu Dhabi, United Arab Emirates
• ⁹ Animal Production Department, National Research Centre, Dokki, Giza 12622, Egypt
• ¹⁰ Department of Animal Production, College of Food and Agriculture Sciences, King Saud University, Riyadh, Saudi Arabia
• ¹¹ Department of Poultry Production, Faculty of Agriculture, Fayoum University, Fayoum, Faiyum, Egypt

One hundred male New Zealand White rabbits aged 5 weeks with an initial body weight of (692.5 ±5.19g) were randomly assigned to four groups (25 rabbits each) for 5-13 weeks of age experimental period. The current study was planned to evaluate the effect of using a combination of selenium (Se)-probiotic rabbit and colistin (COL) as a dietary supplement on growth, nutrient utilization, antioxidant and immune responses, blood metabolites, and cecal fermentation during summer conditions. Four experimental groups in completely randomized design were used. (1) Control group: rabbits received a basal diet (BD) without any added supplements; (2) COL group: rabbits were given BD supplemented with 120 mg of COL/kg;(3) Se+EF group: rabbits consumed BD enriched with 0.3 mg of selenium plus 1 × 10 8 cfu of Enterococcus faecium /kg; and (4) Se+CB group: rabbits were fed BD fortified with 0.3 mg of selenium plus 2.5 × 10 6 cfu of Clostridium butyricum /kg. The results demonstrated that during overall period (5-13 weeks), body weight gain (BWG) and relative growth rate of rabbits consuming diets supplemented with COL, Se+EF, and Se+CB were greater to those of the control group. BWG BW (in groups Se+CB and Se+EF) and feed conversion ratio (FCR) (in groups COL and Se+EF) were improved compared with the control group. Malondialdehyde (MDA) values were declined in rabbits supplemented with Se plus probiotic (Se+CB or Se+EF) compared with the COL and control groups. Serum lipid profile in rabbits received selenium-probiotic combination (especially Se+EF) was improved. Furthermore, antioxidant levels were better in rabbits supplemented with Se plus probiotics compared to the control, and immune responses were significantly enhanced (P < 0.05). In conclusion, supplementing the diets of rabbits with a combination of selenium and probiotics (Se+CB or Se+EF) led to improvements in growth, antioxidant and immune responses, blood metrics, and cecal fermentation under heat stress conditions.