The adverse influences of elevated ambient temperatures during the summer season on the rabbit industry have received increased global attention. Therefore, this study intended to compare the potential effects of nano-selenium (nano-Se) synthesized by biological (BIO) and chemical (CH) methods on growth performance, carcass variables, serum metabolites, and inflammatory cytokines responses of growing rabbits in the summer season. Two hundred and fifty weaned rabbits (males, 35 days of age) were randomly divided into five treatment groups of 50 rabbits each (each group had five replicates with ten male rabbits). Treatment groups were fed a control diet and four controlled diets supplemented with nano-Se synthesized by biological method (BIO25 and BIO50, with a 25 and 50 mg of nano-Se/kg diet, respectively) and chemical method (CH25 and CH50, with a 25 and 50 mg of nano-Se/kg diet, respectively) for eight weeks. During 11 to 13 weeks of age, a gradual enhancement in live body weight (LBW), feed intake (FI) and feed conversion ratio (FCR) was noticed with BIO25 and BIO50 treatments compared to those in the other groups. The carcass percentage was significantly higher (p < 0.01) for animals fed with BIO25 than the other groups. The other organ functions were significantly higher (p < 0.01) in heat-stressed groups compared to that of nano-Se groups. Increasing the level of only BIO from a 25 to a 50 mg/kg diet gave more improvement in the studied parameters. Additionally, the concentrations of serum urea, triglycerides (TG), and glutamyl transferase (GGT) were lower (p < 0.01) in both treated and untreated groups. Likewise, the supplementation with nano-Se (BIO25, BIO50, or CH25) significantly improved the antioxidant indices and inflammatory cytokines responses as indicated from serum metabolites. Based on the study results, nano-Se especially synthesized by the biological method at diet levels of 25 or 50 mg/kg improved the growth performance, kidney and liver functions, carcass traits, antioxidants indices, and inflammatory cytokines of growing rabbits during thermal stress.

The present study aimed to examine the impacts of the supplementation of red or black pepper oils to rabbit diet as growth promoters on New Zealand white (NZW) rabbits. One hundred and forty weaned NZW rabbits were divided randomly into seven groups in a completely randomized experiment using different quantities of red pepper oil (RPO; 0.5, 1.0, 1.5 g/kg diet) or black pepper oil (BPO; 0.5, 1.0, 1.5 g/kg diet), in addition to the control group. Compared to the control, values of live body weight (LBW) for rabbits fed either RPO or BPO enriched diets were greater. The concentrations of serum triglycerides and cholesterol were lower (p < 0.01) in the RPO- and BPO-treated groups than in the control. Immunity parameters and antioxidant indices were improved in treated groups in comparison to the control. Dietary RPO or BPO can affect some growth traits, improve immunity parameters and the antioxidant activity, and decrease the lipid profile and lipid peroxidation. The use of 0.5 g RPO/kg diet as a dietary supplement had a larger effect on growth parameters than the other treatment groups.

This work aimed to explore the effects of dietary supplementation of Chlorella vulgaris (CLV) on the growth performance, carcass traits, hematobiochemical variables, immunity responses, and the antioxidant status of growing rabbits. A total number of 100 rabbits were randomly distributed into four treatment groups, each of five replicates (25 rabbits/group). The experimental groups were as follows; control: a basal diet without supplementation, CLV0.5: basal diet + 0.5 g chlorella powder/kg diet; CLV1.0: basal diet + 1.0 g chlorella powder/kg diet, CLV1.5: basal diet + 1.5 g chlorella powder/kg diet. Live body weight (LBW), cumulative body weight gain (CBWG), feed intake (FI), and feed conversion ratio (FCR) were not affected by dietary CLV supplementation. Platelet count (PLT), hematocrit (HCT), means corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) values were significantly increased in the CLV0.5 group compared with the other treatment groups. Dietary supplementation of CLV (1.5 g/kg diet) significantly reduced the alanine aminotransferase (ALT) activity. The concentrations of serum triglycerides and very low-density lipoprotein (VLDL) were lower (p < 0.05) in the CLV-treated groups than those of the control. Supplemental CLV at all experimental levels gave the best values of immunoglobulins (IgG and IgM) and glutathione activities. Malondialdehyde (MDA) levels were lower in the animals that received CLV in their diet than those of the control group. Dietary supplementation of 1.0 g CLV/kg had the potential to enhance immune responses and antioxidant status, as well as reduce blood lipid accumulation. Therefore, it could be concluded that CLV supplementation to growing rabbit diets can improve the health status.