REGULAR ARTICLES Hematologic, lipid profile, immunity, and antioxidant status of growing rabbits fed black seed as natural antioxidants Yassmine El-Gindy 1 & Hassan Zeweil 1 & Soliman Zahran 1 & Mohamed Abd El-Rahman 1 & Fawzi Eisa 2 Received: 10 October 2018 /Accepted: 20 September 2019 # Springer Nature B.V. 2019 Abstract It is known that using antibiotics by way of growth promoters has harmful side effects on both animals and consumer health due to cross-resistance among pathogens and residues in meat. Using antibiotic to promote growth has been banned in the most countries for this reason; so, we must search for feed additives alternative in animal production. One of them is the black seed (Nigella sativa). Fifty- four growing V-line unsexed rabbits, 4 weeks of age, with an average weight of 776.7 g were randomly allocated to one of three treatments (n = 18): rabbits fed the basal diet (control), rabbits supplemented with either 300 or 600 mg of Nigella sativa seed (NSS)/kg diet. At 12 weeks of age, NSS supplementation significantly improved final body weight, weight gain, feed conversion ratio (FCR), and performance index with significantly reduced feed consumption. Addition of 300 and 600 mg NSS/kg diet resulted in a significant increase in the number of RBCs and WBCs as compared to basal diet group. Compared to controls, NSS supplementation significantly stimulated the IgG and IgM immune responses of rabbits, significantly reduced serum total lipids, triglycerides, and low-density lipoprotein, and significantly increased the high-density lipoprotein concentration. All NSS treatments significantly increased the observed blood total antioxidant capacity and significantly decreased the malondialdehyde values, compared to the basal diet group. In conclusion, the results displayed that addition of NSS in rabbit diets improved productive performance, blood lipid profile, immunity, and antioxidant status, and supplementation with 600 mg/kg NSS was more effective than 300 mg/kg NSS seed supplementation. Keywords Rabbits . Black seed . Immunity . Blood constituents Introduction Antibiotics and many feed additives have been used in the rabbit industry on a substantial scale for quite a while. Recently, many customers wary a lot of antibiotic residues and microbial resis- tance in antibiotics usage in the animal feed industry besides in medical treatment (Tiwari and Dhama 2014). Because of the banning of the antibiotics usage as growth promoters, using al- ternative feed additives or antioxidant substance has accelerated and led to more investigations in animal production (Dhama et al. 2014). Some natural antioxidants were used for this purpose; one of them is a black seed (Nigella sativa). Nigella sativa belonging to family Ranunculaceae had widespread pharmacological activ- ities, such as carminative, antidiabetic, stimulant, analgesic, anti- pyretic and anti-inflammatory, antidiarrheal and antibacterial ac- tivity, antioxidant actions, and protective effect against liver dam- age (Lutterodt et al. 2010). The main compounds of Nigella sativa are thymoquinone (30–48%), p-cymene (7–15%), carva- crol (6–12%), 4-terpineol (2–7%), and t-anethole (1–4%) (Burits and Bucar 2000). Thymoquinone and their derivatives (dithymoquinone, thymolhydroquinone, and thymol) are the pu- tative pharmacologically active ingredients of NSS (Padhye et al. 2008) that could improve growth performance, as well as rabbit health and antioxidant state. The study was aimed to estimate the diets supplemented with Nigella sativa seed on performance, blood lipid profile, and antioxidant state of growing rabbits. Materials and methods Animals and diets Fifty-four growing V-line unsexed rabbits, 4 weeks of age, with an average weight of 777 g were randomly allocated to * Yassmine El-Gindy y.m.elgindy@alexu.edu.eg 1 Department of Animal and Fish Production, Faculty of Agriculture (Saba Basha), University of Alexandria, 22 Tag El-Roassa street, Bokly, Bolkley, Alexandria 21531, Egypt 2 Department of Agriculture Sciences, Higher Institute of Science and Technology, Soq AlKames, Msehel-Trpole, Libya Tropical Animal Health and Production https://doi.org/10.1007/s11250-019-02091-x