Autochthonous probiotic Lactococcus lactis MA5 improves recovery from acute hypoxia stress and resistance to Edwardsiella ictaluri in hybrid catfish (Ictalurus punctatus × I. furcatus)

Dietary supplementation with probiotics is considered an effective strategy to enhance aquaculture production efficiency and disease resistance. Recent research has highlighted the value of using autochthonous probiotics in aquaculture. Herein, an autochthonous probiotic strain ( Lactococcus lactis MA5) isolated from pond-raised hybrid catfish ( Ictalurus punctatus × I. furcatus ) in a previous study was investigated for its ability to improve host recovery from acute hypoxia and resistance to bacterial infection. Hybrid catfish were fed a control diet, or diets containing either 10 4 or 10 6 CFU/g MA5 for 56 days. After the feeding trial, subsets of fish were subjected to either acute hypoxia stress challenge or Edwardsiella ictaluri challenge. Fish fed MA5 exhibited enhanced growth performance without changes to body condition indices. Following acute hypoxia challenge, MA5-supplemented fish showed increased blood hemoglobin, red blood cell counts, and total protein concentration compared to the control. In addition, MA5 led to upregulated expression of gpx1, a gene encoding an antioxidant enzyme, in the intestine. Lastly, fish fed 10 6 CFU/g of MA5 displayed significantly higher survival when exposed to E . ictaluri . These data suggest dietary supplementation with the autogenous probiotic L. lactis MA5 can promote growth, support acute hypoxia recovery, and improve resistance to E. ictaluri in hybrid catfish.