نوع مقاله : مقاله پژوهشی
نویسندگان
گروه شیلات، دانشکده علوم دامی و شیلات، دانشگاه علوم کشاورزی و منابع طبیعی ساری، ساری، مازندران
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Introduction: Ornamental fish are aquatic animals primarily reared in aquariums and decorative ponds for aesthetic purposes rather than human consumption. Among freshwater ornamental species, koi carp (Cyprinus carpio var. koi) is one of the most popular due to its remarkable diversity of colors and patterns, which significantly determine its market value. Therefore, understanding pigments and their dietary sources is essential in ornamental aquaculture. Carotenoids are the main compounds responsible for coloration in ornamental fish, however, fish species such as koi cannot synthesize them independently and must obtain them through feed. Astaxanthin, an important carotenoid with strong antioxidant properties, supports health, immunity, and skin coloration. Lysophospholipids may enhance fat-soluble compound absorption, improving astaxanthin uptake. This study evaluated their effects on pigment absorption, immunity, and antioxidant indices in koi carp.
Materials and Methods: A total of 150 koi carp (with an initial mean weight 3.63 ± 0.05 g) were purchased from a local farm and transferred to a private rearing facility. After a two-week acclimation period on a commercial ornamental fish diet, the fish were randomly distributed into 15 glass aquaria (60 L; 60 × 45 × 20 cm) with 5 treatments, 3 replicates, and 10 fish per aquarium. Water quality was maintained by filtration, at temperature 26 ± 1°C, pH 7.5 ± 0.5, and dissolved oxygen 7 ± 0.5 mg/L. Synthetic astaxanthin (>98% purity) and lecithin-based lysophospholipid were added to the basal diet by spraying with canola oil. Treatments included: control, 0.01% astaxanthin, 0.02% astaxanthin, 0.01% astaxanthin + 0.1% lysophospholipid, and 0.02% astaxanthin + 0.1% lysophospholipid. Fish were fed at 5% body weight, three times daily, for 56 days. At the end of the feeding trial, serum lysozyme, alternative complement activity (ACH50), immunoglobulin, and antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were measured using standard spectrophotometric methods. Serum, skin, and fillet carotenoids were also assessed. Data were analyzed using One-Way ANOVA followed by Duncan’s test in SPSS version 19, with significance set at P<0.05.
Results: According to the immune parameters, lysozyme activity was significantly lower in the control and diet containing 0.01% astaxanthin compared to other groups (P<0.05). Immunoglobulin and complement activities were also significantly influenced by the different diets, with the combined astaxanthin–lysophospholipid groups showing the highest values (P<0.05). The highest CAT activity was recorded in fish fed the diet containing 0.01% astaxanthin supplemented with 0.1% lysophospholipid (P<0.05). The lowest SOD activity was observed in the control and 0.01% astaxanthin groups, while the addition of lysophospholipid to diets containing astaxanthin significantly increased SOD activity (P<0.05). Likewise, fish receiving the combination of lysophospholipid and astaxanthin, as well as the diet containing 0.02% astaxanthin, showed higher GPx activity than the control group (P<0.05). Carotenoid accumulation in the skin and fillet was significantly higher in fish fed astaxanthin-supplemented diets, particularly when combined to lysophospholipid (P<0.05).
Discussion: Assessment of immune parameters in fish is an important indicator of health and immune efficiency, since these markers reflect both innate and acquired defense capacity. In the present study, adding astaxanthin to lysophospholipid synergistically improved lysozyme, complement, and immunoglobulin activities. This effect was probably due to better astaxanthin absorption caused by lysophospholipid, which enhances bioavailability through mixed micelle formation and facilitation of lipid transport. Antioxidant enzymes such as SOD, CAT, and GPx play crucial roles in mitigating oxidative stress and maintaining fish health. Here, astaxanthin-containing diets increased antioxidant enzyme activities compared to the control, and the best antioxidant performance was observed with combination of 0.01% astaxanthin and 0.1% lysophospholipid. This suggests a synergistic effect between the two additives. Similar improvements in antioxidant capacity have been reported in trout, tilapia, shrimp, and other aquatic species. Astaxanthin also increased carotenoid deposition in koi skin and fillet, improving pigmentation and likely market value. The inclusion of lysophospholipid further enhanced carotenoid accumulation in tissues, probably by improving emulsification and intestinal uptake of this fat-soluble pigment. In contrast, lower serum carotenoid levels in combined treatments may indicate faster transfer from blood to target tissues.
Conclusion: Based on the present research, it can be stated that the combination of lysophospholipid and astaxanthin, particularly at the 0.01% level, likely enhanced tissue deposition of astaxanthin, which may reflect improved bioavailability, and concurrently improved antioxidant capacity and immune function.
کلیدواژهها [English]
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