Effects Of Mannase On Growth, Metabolism And Non-specific Immunity Of Tilapia (GIFT, Oreochromis Niloticus)

As we all know, vegetable protein sources with extensive distribution are more abundant and less expensive than fish meal (FM). Although FM is a kind of high-quality protein source, it is widely replaced by vegetable protein sources in aquatic feed because of its shortage and high price. However, the Non-Starch Polysaccharides (NSP) in vegetable protein sources is an anti-nutritional factor. NSP is mainly present in the cell walls of plant cells, and it can’t be digested and utilized by fish due to the lack of endogenous NSP enzymes within fish’s digestive system. So NSP restricts the use of vegetable protein sources in aquatic feed. Many studies show that NSP enzymes can effectively improve the nutrients digestibility and utilization by the animals, enhance the immunity in animals, and further improve the growth performance of the animals. Mannase is a kind of NSP enzymes which can effectively eliminate or ease the anti-nutritional effects of mannan in feed. A large number of researches about the effect of mannase on livestock and poultry have been reported, and it has been widely used in the feed of livestock and poultry. But its effect on fish has not been reported. Therefore, this study explored the effects of mannase on growth performance, metabolism, and non-specific immunity of tilapia (GIFT, Oreochromis niloticus), in order to enrich research data of mannase on aquatic animals and provide the basis for scientific use of mannase in aquatic feed. The main contents and results are as follows.1. Effects of dietary neutral mannase on growth, metabolism and non-specific immunity of tilapia (GIFT, Oreochromis niloticus)The present study was conducted to investigate the effects of dietary neutral mannase supplementation on growth performance, metabolism, and non-specific immunity of tilapia (GIFT, Oreochromis niloticus). Three isonitrogenous and isoenergetic experimental diets were foumulated by supplementing with0(control),500and1000U/kg neutral mannase (enzyme activity of9000Ug-1product at50℃and pH6.0), respectively. Each diet was randomly fed to one group offish with an initial average weight of (5.80±0.01) g for8weeks. Each group had3tanks with30fish per tank. The results showed as follows: the final weight, specific growth rate (SGR) and protein efficiency ratio (PER) of tilapia in the1000U/kg group were significantly higher than those in the other groups (P<0.05). No significant differences were found in feed conversion ratio (FCR), feed intake (Fl) and survival rate (SR) of all groups(P>0.05). With the increase of mannase supplemental level, the amylase, trypsase and Na+,Ka+-ATPase activities in intestine of tilapia were significantly increased (P<0.05). The aspertate aminotransferase (AST) activity and high-density lipoprotein cholesterol (HDL-C) content in serum of tilapia in the1000U/kg group were significantly lower than those in the control and500/kg group(P<0.05), but the total cholesterol (TC) and very low density lipoprotein cholesterol (VLDL-C) content were significantly higher than those in the control group and500U/kg group (P<0.05). No significant differences were found in total superoxide dismutase (T-SOD) activity, alanine aminotransferase (ALT) activity, total triglyceride (TG) content, low density lipoprotein cholesterol content (LDL-C) in serum and total leukocyte cells (WBC) in blood in all groups (P>0.05). The neutral mannase supplementation also led to an increase (P<0.05)in the percentage of neutrophils, the percentage of moncytes in blood, the alkaline phosphatase (AKP) activity and catalase (CAT) activity in serum (P<0.05), but the percentage of lymphocyte in blood was significantly lower than that in control group (P<0.05). These results indicated that dietary neutral mannase supplementation could improve feed utilization rate, increase the non-specific immunity, and promote the growth of tilapia.1000U/kg should be the adaptive supplemental level of neutral mannase in the feed of tilapia.2. Effects of dietary acidic mannase on growth, metabolism and non-specific immunity of tilapia (GIFT, Oreochromis niloticus)The present study was conducted to assess the effects of dietary acidic mannase supplementation on growth performance, metabolism, and non-specific immunity of tilapia. Three experimental diets contained0(control),400and800U/kg acidic mannase (enzyme activity of5000Ug-1product at65℃and pH3.8), respectively. Each diet was randomly fed to one group of fish with an initial average weight of (5.80±0.01) g for8weeks. Each group had3tanks with30fish per tank. The results showed that no significant differences were found in the final weight, SGR, PER, FCR and FI among all groups (P>0.05). The amylase activity in intestine of tilapia in800U/kg group was significantly higher than that in the other groups (P<0.05). The acidic mannase supplementation also increased (P<0.05) the trypsase activity in intestine. With the increase of mannase supplemental level, the Na+,K+-ATPase activity in intestine was significantly increased (P<0.05). However, dietary mannase supplementation had no significant effect on ALT and AST activities in serum, and the TC, TG, HDL-C, LDL-C, VLDL-C content in serum (P>0.05). The CAT activity in serum of tilapia was significantly increased (P<0.05) with the increase of mannase supplemental level. The AKP, T-SOD activities in serum in800U/kg group is significantly higher than that in the other groups (P<0.05). There were no significant differences in the blood WBC and the percentage of neutrophil in blood among all groups(P>0.05).The percentage of monocyte in blood in800and400U/kg group is significantly higher than that in the control group (P<0.05), while the percentage of lymphocyte was significantly lower than that in the control group (P<0.05). Thus, acidic mannase addition to tilapia diets improved the ability of digestion and non-specific immunity of tilapia, but without the growth performance.3. Effects of dietary compound mannase on growth, metabolism and non-specific immunity of tilapia (GIFT, Oreochromis niloticus)The present study was conducted to investigate the effects of dietary compound mannase on growth performance, metabolism, and immunity of tilapia fed SBM-based diets. Three dietary treatments contained0(control),68and136mg/kg compound mannase, respectively. Each treatment contained3tanks with30fish per tank. Trials lasted8weeks. Our results demonstrated that the compound mannase addition (68and136mg/kg) improved (P<0.05) the final weight, SGR, PER and FCR compared with the control (0mg/kg). There were no significant differences in FI and SR among the3dietary treatments (P>0.05). The compound mannase supplementation also led to an increase (P<0.05) in amylase, trypsase and Na+, K+-ATPase activities in intestine, and an decrease (P<0.05) in AST and ALT activities in serum compared with the control. However, dietary enzyme supplementation had no significant effect on TG, TC, HDL-C, LDL-C and VLDL-C (P>0.05) in serum. Moreover, the compound mannase addition increased (P<0.05) the WBC, percentage of neutrophils, percentage of moncytes in blood, T-SOD activity and CAT activity in serum. No significant differences in AKP activity were detected among the treatments (P>0.05). In conclusion, the compound mannase addition to tilapia diets improved feed utilization and non-specific immunity resulting in improvements in growth performance.68mg/kg should be the adaptive supplemental level of the compound mannase in the feed of tilapia.