Oral administration of bovine lactoferrin inhibits bacterial infection in tilapia and elevates survival after bacterial infection: an examination of its immune-modulating properties

Abstract

It was previously reported that the oral administration of lactoferrin (LF) provides antimicrobial activity in animals against bacterial and viral infections and is involved in immunomodulatory properties. In this report, a hybrid strain of Oreochromis nilotica (male) × O. mossambicus (female) was fed homemade diets with or without supplementation with 10, 50, 100, and 150 mg bovine LF g−1 feed for 60 days. After dietary treatment, the experimental fish were infected with Streptococcus agalactiae. LF supplementation resulted in a significantly higher survival rate and suppression of bacterial growth at 24–96 h in the liver, spleen, kidneys, eyes, and gills. A reduction in peroxidase activity was followed by a similar reduction in the peroxidase content of leukocytes at 24 h as analyzed by spectrophotometry. Respiratory burst (RB) activity was detected regardless of the time at which LF was administered to fish in relation to the bacterial infection. A beneficial effect of LF on RBs was also detected before bacterial challenge (with 100 mg LF/g) and 24 h after bacterial challenge with 150 mg/g. The results obtained validate LF’s beneficial effects on RBs by phagocytes in tilapia, which was only shown at 48 h after supplementation with 100 mg bovine LF g−1 feed after the bacterial infection. Moreover, after oral administration of LF, it was detected in the mucosa of the small intestines of tilapia. In conclusion, we demonstrate a reduction in fish mortality after the oral administration of LF, and we examined its immunomodulatory properties in tilapia.