Submitted to: International Aquaculture Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 15, 2006
Publication Date: August 1, 2006
Citation: Welker, T.L., Lim, C.E., Aksoy, M., Klesius, P.H. 2006. Effect of dietary bovine lactoferrin on disease and stress resistance of Nile tilapia (Oreochromis niloticus). Symposium of the Comparative Nutrition Society. August 4-9, 2006. Pages 208-212. Technical Abstract: Juvenile Nile tilapia (Oreochromis niloticus) were fed nutritionally complete, practical basal diets supplemented with bovine lactoferrin (Lf) at 0, 200, 400, 800, or 1600 mg/kg diet to apparent satiation twice daily for 8 weeks. At the end of the feeding trial, the effect of dietary Lf on growth performance, immune function, and resistance to Streptococcus iniae challenge and low-water stress was determined. Dietary Lf did not affect growth performance (weight gain, feed intake, feed efficiency ratio, or survival) or hematological parameters (hemoglobin, white and red blood cell counts, or hematocrit) (P<0.05). Level of Lf in diet had a significant impact on mortality from S. iniae (P<0.05) Cumulative mortality was highest in control fish, declined with increasing dietary level of Lf from 200 to 800 mg/kg, and increased slightly in the group fed 1600 mg/kg. Fish fed 800 mg/kg had significantly lower mortality from S. iniae than control fish. There was not a corresponding increase in activity of non-specific or specific immune parameters (plasma lysozyme and hemolytic complement activities or agglutination antibody titer to S. iniae) with addition of Lf to diets (P>0.05), but plasma iron decreased and total iron binding capacity (TIBC) increased significantly with increasing concentration of Lf in diet (P<0.05), which appeared to correspond with the decrease in mortality from S. iniae. The ability of Lf to sequester iron, an essential nutrient required for the growth of bacteria, is regarded as one of its key antibacterial properties. Crowding stress produced significant increases in plasma cortisol, glucose, lactate, and osmolality from baseline values (P'0.001), but dietary Lf did not significantly affect plasma glucose, osmolality, or cortisol concentrations (P>0.05). However, the increase in cortisol from baseline values to post-stress was considerably smaller for fish fed 400 and 800 mg/kg, and in fish fed 400 mg/kg, there was no noticeable difference between baseline and post-stress cortisol values. The duration of most studies examining the effects of dietary Lf on fish health have been 30 days or less. Beneficial effects of Lf on some non-specific immune functions, and also the response to stress, may have occurred if the feeding duration were shorter. We also cannot rule out that disease resistance may have been greater after a shorter feeding period.