Effects of dietary bovine lactoferrin on growth, physiological performance, iron metabolism and non-specific immune responses of Siberian sturgeon Acipenser baeri.

The present experiment was carried out to investigate the effects of different levels of dietary lactoferrin (LF) on growth performance, physiological status, iron absorption and innate immune response of juvenile Siberian sturgeon Acipenser baeri. Fish were fed with six different rations including 0, 100, 200, 400, 800 and 1600 mg LF kg(-1) diet for 8 weeks. At the end of the experiment, samples were collected for estimating the physiological and immunological parameters. Dietary LF did not change the fish growth performance, hematological parameters, serum proteins or hepatic enzymes. Moreover, stress indicators (plasma cortisol, glucose and lactate) were not affected by dietary LF. The iron absorption of fish was considerably affected by LF; thus, plasma iron in LF-treatments greatly declined and the total iron binding capacity (TIBC) significantly increased in fish fed with 800 mg LF kg(-1). In addition, the liver iron content markedly increased in some LF-treatments, but the variation of muscle iron concentration in treatments was insignificant. The amount of mucus secretion and serum bactericidal activity rose in fish fed on dietary LF, although other non-specific immune responses such as mucus bactericidal activity, serum and mucus lysozyme activity, serum peroxidase, serum natural hemolytic complement activity and serum IgM were not influenced by LF. This study revealed the ability of dietary LF to sequester iron, which is an essential nutrient required for the growth of bacteria. LF was also shown to improve some physiological and immunological parameters of Siberian sturgeon, to some extent.
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