*4.5. Antioxidants*

Oxidative stress is defined as an imbalance between pro- and anti-oxidant species, which leads to molecular and cellular damage [93]. The oxidative damages could be mitigated by endogenous defense systems, such as CAT, SOD, and GPX system, but this system is not completely efficient, especially under stress [94]. The determination of single components of this system or so-called TAC could reveal the efficiency of enzymatic and non-enzymatic antioxidative systems [95].

Vegetable oils, such as olive oil, rice bran oil, corn germ oil, and wheat germ oil have been used as a source of plant antioxidants [96,97]. In the current findings, the oral administration of RSO and WGO or their mixture showed a significant decrease in TBARs and a significant increase in blood serum antioxidant properties (CAT, SOD, and TAC). In accordance with the present results, the treatments with RSO and WGO have a positive effect on the antioxidant status, as they are very efficient scavengers of free radicals [18,98]. Whereas, RSO decreases hepatic lipid peroxidation as a result of increasing hepatic SOD activity [12]. In addition, RSO has a high content of natural antioxidants, such as phenolic compounds [99].

Wheat germ oil has a positive effect on the antioxidant defense system [23] due to its content of antioxidant compounds, such as alpha, beta, and gamma-tocopherols, tocotrienols [22], and fat-soluble carotenoids, such as lutein, zeaxanthin, and beta-carotene [24].Moreover, WGO has remarkable antioxidant effects owing to the individual and synergistic effects of fatty acids, antioxidants, vitamins, phytosterols, and phenolic compounds [24,100]. Another prospective interpretation is that WGO promotes the tocopherol-mediated redox system and prevents the synthesis of eicosanoids (prostaglandins) that stimulate the lipid peroxidation process [101].

#### *4.6. Antibody Titers against SRBCs*

Antibody titers against SRBCs of growing rabbits were improved significantly by oral administration of RSO, WGO, and their mixture. These results sugges<sup>t</sup> that RSO, WGO, and their mixture might have synergistic effects on immune responses. In harmony with the current findings, the addition of 1 g RSO/kg diet or 1 g onion seed oil/kg diet and their combination in the growing rabbit's diet improved (*p* ≤ 0.05) antibody titer against SRBCs compared to the control group [17]. Moreover, dietary supplementation with watercress oil plus coconut oil resulted in improvement in the immunity of growing rabbits and may be associated with a reduction in pathogenic cecal bacteria and enhancing the antioxidant status [18].

The improvement of antibody titer against SRBCs may be due to carotenoids found in Rocket, *E. Sativa*, which can conserve phagocytic cells from antioxidative defects, improve T and B lymphocyte proliferative responses, and ameliorate the production of inevitable interleukins [102]. Moreover, carotenoids raise plasma IgG levels [103]. WGO contains higher amounts of vitamin E (more than approximately 50 mg vitamin E/100 g oil), whereas dietary vitamin E combined with Se in diets caused an improvement in the antibody titers against SRBCs of growing rabbits [65]. Otherwise, WGO is rich in n-3 PUFA as reported in the current study (Table 3 and Figure 3), mainly alpha-linolenic acid, which recovers the immune system [104].
