A mixture of Chinese herbs and a commercial probiotic Bacillus species improves hemato-immunological, stress, and antioxidant parameters, and expression of HSP70 and HIF-1α mRNA to hypoxia, cold, and heat stress in Nile tilapia, Oreochromis niloticus

A 56-day feeding trial was performed to evaluate the effect of herbal-probiotic supplements comprising a mixture of Chinese herbs (CH) (i.e., Astragalus membranaceus, Angelica sinensis, and Crataegus hupehensis) and or commercially prepared probiotic Bacillus species (BS) (i.e., spores of B. subtilis and B.licheniformis) on the physiological response of Nile tilapia. Fish (50 ± 2 g) were fed six diets in duplicates including a control (CT) enriched with BS [at 10 g kg−1], CH [at 10 g kg−1], CHBS1 [CH at 3 g kg−1 and BS at 7 g kg−1], CHBS2 [CH at 5 g kg−1 and BS at 5 g kg−1], and CHBS3 [CH at 7 g kg−1 and BS at 3 g kg−1] for a period of 56 weeks. At the end of the feeding trial, some hemato-immunological parameters and antioxidant indices, as well as stress-related genes in tilapia, were evaluated; and afterwards exposed to hypoxia for 18 h and to cold and heat each for 2 h. The results showed increased hematocrit, red blood cells, haemoglobin, and white blood cells, in fish blood in most of the herbal-probiotic groups compared to the control group (P < 0.05). Lowered cortisol, glucose, as well pyruvate kinase, alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase, and increased myeloperoxidase, total antioxidant capacity, superoxide dismutase, and catalase activities were observed in the serum of all herbal-probiotic groups over the control group (P < 0.05). Besides, all herbal-probiotic groups showed increased expression of heat shock protein 70 and hypoxia-inducible factor 1 alpha mRNAs in the livers of fish (P < 0.05). Among the herbal-probiotic groups, tilapia fed with CHBS2 diet showed enhanced values in most of the indices measured under the different stress conditions (P < 0.05). These findings suggest CHBS2 supplement as a prophylactic against the suppressive effects of stress in tilapia.