Effect of Probiotics and Dietary Levels of Protein on Growth, Muscle Quality and Expression of Some Immune Genes in the Head Kidney of Nile Tilapia (Oreochromis Niloticus)

Abstract

M T Ridha, I S Azad, M A Hossain and S El-Dakour

This study evaluated the effect of dietary probiotics (P) to enhance the feed quality, growth parameters, muscle fatty acid (FA) profile, immunity, and the stimulation of immune genes in head-kidney of Nile tilapia. Healthy mixed-sex Nile tilapia (47.0 ± 2.07 g mean weight), were fed three tilapia commercial feeds; S, A, and a local feed K having 33.3, 32.4, and 13.4% protein, respectively. Dietary supplementation of Bacillus probiotic (P) into the commercial feeds resulting in six experimental feeds (S, SP, A, AP, K, and KP) were used. The non-probiotic feeds served as controls and each treatment had three replicates. Results showed that fish fed the SP feed had the highest (P<0.05) final mean weight (582.7 g), daily growth rate (2.52 g/fish/day), gross fish yield (44.0 kg/m3), and best feed conversion ratio (1.9), followed by S (570.4 g, 2.46 g/fish/day, 41.1 kg/m3, and 2.09, respectively). However, these values were the lowest (P<0.05) in tilapia fed KP and K (362.8 and 366.7 g, 1.48 and 1.49 g/fish/ day, 27.4 and 26.8, kg/m3, 2.16 and 2.18, respectively). The feed A and AP had intermediate values. Fish fed the SP feed had the highest (P<0.05) muscle ∑n-3 fatty acid (10.5) and ∑n-3/n-6 ratio (0.75). In general, gut bacterial counts, lysozyme activity, phagocytic activity, and hemagglutination titer were the highest (P<0.05) in tilapia fed the SP, followed by tilapia fed AP, but it was the lowest for tilapia fed K and the KP feeds. Probiotics significantly up regulated β-actin, IgM, IL-β1, Mx, and TNF-α immune gene in the head kidney with better response in fish fed the SP feed. It can be concluded that improvement in tilapia growth, bacterial colonization, muscle quality, immune parameters, and the up regulation of immune genes in the head kidney due to probiotic supplementation would depend on the protein level of the feed used.

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