Effect of dietary astaxanthin against Aeromonas hydrophila infection in common carp, Cyprinus carpio

• Very low mortality 10% and 20% was observed in 50 and 100 mg kg−1 diets.
• Growth rate was increased with all doses from week 1 to 4.
• RBC, WBC, Hb, Ht increased in 50 and 100 mg kg−1 diets.
• Respiratory burst activity increased in 50 and 100 mg kg−1 diet on weeks 2 and 4.
• Lysozyme activity and bactericidal activity enhanced in all diets.

The effect of astaxanthin at 0, 25, 50, and 100 mg kg−1 incorporated in basal feed on immune response and disease resistance in Cyprinus carpio against Aeromonas hydrophila was investigated. When fed with 25 mg kg−1 diet, the cumulative mortality was 35% whereas it was 10% and 20% with 50 and 100 mg kg−1 diets. With all enriched diets the growth rate increased significantly from week 1 to 4 when compared with control. However, the specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) did not vary significantly from that of the control except with 50 mg kg−1 diet. When fed with 50 and 100 mg kg−1 diets the red blood cells, white blood cells, hemoglobin, and hematocrit values significantly increased. However, the serum total protein, albumin, and globulin contents significantly increased only when fed with 50 and 100 mg kg−1 diets. The phagocytic ratio also significantly raised with 50 and 100 mg kg−1 diets on week 2 and 4 whereas the phagocytic index significantly increased with all groups only on fourth week. The respiratory burst activity significantly increased in 25 mg kg−1 diet group on first week whereas in 50 and 100 mg kg−1 diet groups the activity increased on weeks 2 and 4; a similar trend was observed in the anti-protease activity only on weeks 2 and 4. The serum lysozyme activity and bactericidal activity registered a significant increase with all enriched diets. This study suggests that supplementation of astaxanthin at 50 and 100 mg kg−1 with the basal diet significantly promotes the growth restores hematology and modulates the immune system in C. carpio against A. hydrophila.