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Use of diet crossover to determine the effects of β-glucan supplementation on immunity and growth of Nile Tilapia Oreochromis niloticus
- Welker, Thomas L., Lim, Chhorn, Yildirim-Aksoy, Mediha, Klesius, Phillip
- Journal of the World Aquaculture Society 2012 v.43 no.3 pp. 335
- Oreochromis niloticus, Streptococcus iniae, aquariums, catfish, feed conversion, feed supplements, immunity, lymphocytes, weight gain
- Juvenile Nile tilapia were fed either a basal (control) diet (n = 6 aquaria) or a diet supplemented with 1 g/kg β-glucan (n = 24 aquaria) for 4 wk. At the end of this period, fish receiving β-glucan were continued on the same diet (n = 12 aquaria) or switched to the control diet (n = 12 aquaria) for 2 wk. After 6 wk, tilapia continuously fed the β-glucan supplemented diets had improved weight gain and feed efficiency than those fed the control diet uninterrupted or switched from the β-glucan diet to the control after 4 wk. Feeding tilapia β-glucan for 4 wk and then switching to the basal diet for 2 wk caused a significant increase in the respiratory burst of polymorphonuclear lymphocytes (17.77 × 103 units/1000 white blood cells [WBC]) compared to catfish fed the control diet (13.50 × 103 units/1000 WBC) or the β-glucan diet continuously (13.57 × 103 units/1000 WBC), but other immune parameters were unaffected. Tilapia were then challenged with Streptococcus iniae. The two groups were divided again (n = 6 aquaria) postchallenge and continued on the same diet or switched to the other diet (β-glucan or control) for another 3 wk. No differences in survival to S. iniae infection occurred between dietary groups.