## 4 Discussion
Thus, although an enhancement in animal performance might occur, the major expected benefit of EO-OG dietary supplementation is health stimulation. Prawns fed a diet with 3.0 g kg\({}^{-1}\) EO-OG showed longer antenna lengths than prawns from all of the other experimental groups. Antennae are among the main chemosensory organs of decapods and are used for social interaction [62; 63]. The antenna length is a physical feature that indicates the welfare status of decapods. Measurement of antenna length can be used as a non-invasive method to infer the welfare of farmed decapods. Long and intact antennae are signs of healthy animals in adequate ambient conditions, while damaged or shortened antennae may suggest poor health and a deteriorated welfare status [64; 65]. Thus, based on the longer antennal lengths, dietary supplementation with 3.0 g kg\({}^{-1}\) EO-OG supported the prawns' antenna-related welfare. A future study on prawn behavior may assess how EO-OG supplementation benefits antenna-related behaviors such as competitive interactions, social communication, and mating receptivity. Normal intracellular reactions and the phagocytic process generate oxidizing compounds such as reactive oxygen species (ROS) and reactive nitrogen intermediates (RNIs). Nevertheless, when in excess, these oxidizing compounds are toxic to the organism's tissues and need to be neutralized by the antioxidant defense system [66]. The antioxidant defense system is divided into enzymatic (inc. enzymes such as SOD, CAT, and GPx) and non-enzymatic, which in turn can be endogenous (e.g., GSH) or exogenous (e.g., acquired from the diet). The enzyme CAT catalyzes hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) into water (H\({}_{2}\)O) and oxygen (O\({}_{2}\)), after the enzyme SOD has catalyzed the superoxide anion (O\({}_{2}\)\({}^{-}\)) into H\({}_{2}\)O\({}_{2}\), maintaining a balanced cellular redox status [67]. In this study, prawns fed a diet supplemented with 3.0 g kg\({}^{-1}\) EO-OG showed increased CAT enzymatic activity, which suggests a potential antioxidant effect of dietary EO-OG. Likewise, the oxidative damage caused by oxidizing compounds leads to lipid peroxidation [68]. Prawns supplemented with EO-OG, regardless of the inclusion level, displayed decreased lipid peroxidation, which is an indication of a greater efficiency of the antioxidant system of prawns fed with EO-OG. Addressed together, the increased CAT activity may indicate an indirect antioxidant effect of EO-OG that facilitated the decrease in organic peroxides, observed by the diminished lipoperoxidation. The immune system of decapods relies on innate mechanisms and is mediated by defense cells, physical barriers, and humoral responses. These innate defense mechanismsare intrinsically related to animal health and welfare [69; 70; 71]. The antioxidant system has a fundamental role in the deactivation of oxidizing compounds formed naturally by physiological processes. Therefore, dietary immunostimulants may enhance decapods' non-specific defense responses. Notably, the confinement condition of the production systems is a source of chronic stress which can impair the health and welfare of farmed animals, including shrimp and prawns [72; 73; 74]. Therefore, the use of EO-OG as a potential natural antioxidant can be considered a beneficial management tool to enhance prawns' health. Typically, the antioxidant system components (enzymatic and non-enzymatic) operate in concert to maintain body homeostasis. Different antioxidants target different ROS, and they exhibit distinct reaction rates and different mechanisms of action. Our findings indicate that the antioxidant effect of the essential oil is not directly related to classical GSH cycling. First, GSH acts directly in the sequestration of ROS, serving as a reducing agent for disulfides, hydroperoxides, and other electrophilic substances. It may also be involved in the recycling of other antioxidants, such as vitamins C and E, thereby providing reducing power to maintain their reduced forms.