Immune Status of Bighead Catfish (Clarias macrocephalus Günther, 1864) Crossbreeds Between Wild and Domesticated Strains and Their Response to Challenge With Aeromonas hydrophila

Aeromonas hydrophila is a major pathogen causing septicemic disease and high mortality in cultured bighead catfish, Clarias macrocephalus Günther, 1864. Crossbreeding for enhanced disease resistance may help alleviate the infection. This study aimed to evaluate the crossbreeding effects of bighead catfish from three broodstock sources, including one domesticated strain (Can Tho - CT) and two wild strains (Ca Mau - CM and Hau Giang - HG), on the innate immune response. Eight diallel crosses (excluding HG × CT) were reared in tanks for 100 days to the juvenile stage for use in this study. Forty-five bighead catfish juveniles of similar sizes, 4.5–6.1 g, were sampled from each cross to evaluate the immune response and stress indicators. Thirty fish from each cross were challenged with A. hydrophila. The results showed that innate immune responses of domesticated CT strains were higher than wild strains (HG and CM). Higher values of white blood cells, phagocytic activity, and lysozyme activity were observed in CT × CT and CT × CM crosses. These crosses had significantly lower cortisol levels and lower mortality rates of 40 % (CT × CT) and 43.3 % (CT × CM) after being challenged with A. hydrophila compared to the other crosses. The results demonstrate that domesticated CT strain and crossbreeding between CT and CM wild strains could improve the innate immune system and resistance to A. hydrophila. The innate immune responses of the domesticated CT strain were higher than wild strains (HG and CM).