Abstract
This study evaluated the effects of dietary astaxanthin on sperm quality and physiological indicators of pubertal male Nile tilapia, Oreochromis niloticus (Linnaeus, 1758). Fish (32.42 ± 0.51 g) were allocated to 16 tanks in recirculating aquaculture system (220 L; 5 fish tank(-1)), with four replicate tanks per dietary treatment, and fed for 45 days with diets containing 0, 50, 100, and 150 mg kg(-1) astaxanthin derived from microalgae Haematococcus pluvialis. Astaxanthin supplementation markedly improved seminal traits: males receiving 50-150 mg kg(-1) exhibited significantly greater semen volume, sperm concentration and motility, and a higher proportion of morphologically normal sperm than controls (P < 0.05). Semen from supplemented groups also showed reduced catalase activity and malondialdehyde levels (P < 0.05), indicating lower oxidative stress. Growth performance and survival did not differ among treatments (P > 0.05). Hematologically, astaxanthin, particularly at 100-150 mg kg(-1), increased lymphocyte proportions while decreasing circulating neutrophils, monocytes, and thrombocytes (P < 0.05). Serum biochemistry indicated changes in metabolic status at 100-150 mg kg(-1), with reduced glucose, total cholesterol, triglycerides, alanine aminotransferase, and aspartate aminotransferase, and elevated total protein, albumin, and globulin (P < 0.05). Collectively, these findings indicate that dietary astaxanthin, particularly at 100-150 mg kg(-1), supports semen quality and physiological status in pubertal male Nile tilapia without compromising growth.