Application Of Four Kinds Of Feed Additives In Diets Of GIFT, Oreochromis Niloticus

1. An 9-week feeding experiment was performed to investigate the effects of dietary bile acids levels on growth performance, body composition, serum biochemical indicators and hepatic metabolism in juvenile GIFT strain(Genetically Improved Farmed Tilapia) of Nile tilapia Oreochromis niloticus(Initial body weight: 8.16±0.24 g). Five practical diets were formulated with incorporation of bile acids at the levels of 0(control), 50, 150, 450 and 1350 mg/kg. Our results are as follows: 1) compared with those in the other groups, the highest weight gain rate(WGR), specific growth rate(SGR) and feed efficiency(FE) were observed for fish fed the diets containing 150 mg/kg bile acids. In contrast, the activity of serum alanine aminotransferase(ALT) in group fed on bile acids at 150 mg/kg levels was significant lower than that in the control group(P< 0.05). 2) dietary bile acids supplementation can significantly reduce the content of crude lipid in GIFT whole body, muscle and liver(P< 0.05), whereas increase obviously the levels of high-density lipoprotein cholesterol(HDL-C) and low-density lipoprotein cholesterol(LDL-C)(P< 0.05); 3)results for several parameters detection on nutrient metabolism in the liver and intestinal showed, enzymatic activities of lipoprotein lipase(LPL), hepatic lipase(HL), total lipase(TL) and lipase(LPS) increased significantly with the dietary bile acids levels, but lower malondialdehyde(MDA) content was observed in liver than control group(P< 0.05). In addition, liver slices of tilapia treated with dietary bile acids addition at 1350 mg/kg showed a large number of hepatocytes with empty vacuoles, nuclear migration and some visible white-block gallstones in gallbladders. All the above results indicated that appropriate dietary bile acids supplementation could improve growth performance and feed efficiency, promote lipid degradation, decrease fat accumulation and alleviate the liver injure in juvenile tilapia. Based on the broken-line regression analysis of WGR and feed efficiency, 189 mg/kg of bile acids levels seemed optimal for juvenile GIFT, Oreochromis niloticus.2. A 9-week feeding experiment was performed to investigate the effects of dietary silymarin levels on growth performance, hepatic lipid metabolism enzymes activities and antioxidant ability in juvenile GIFT(Oreochromis niloticus)(initial body weight: 8.17±0.31g). Five practical diets were formulated with incorporation of silymarin at the levels of 0(control), 100, 200, 400 and 800 mg/kg. At the end of the feeding trial, growth performance, body composition, serum biochemical indices, hepatic lipid metabolism enzymes activities and antioxidant enzymes activities were measured. The results were as follows: 1) Compared with those in the other groups, the highest WGR, SGR and condition factor(CF) were observed for fish fed the diets containing 100 mg/kg silymarin. On contrast, feed conversion rate(FCR) of the fish fed the diets containing 100 mg/kg silymarin was the lowest and significantly decreased compared with control group(P< 0.05). Dietary silymarin supplementation significantly decreased hepatosmatic index(HSI) and viscerosmatic index(VSI), There were no significantly difference of survival rate(SR) among all the groups(P> 0.05). 2) The lipid content in whole body, muscle and liver were the lowest at the group of 100 mg/kg diet and significantly lower than the control group(P< 0.05). Dietary silymarin supplementation significantly decreased triglyceride(TG) in serum(P< 0.05). The activities of serum aspartate transaminase(AST) and ALT were both decreased initially and then increased as silymarin level increased, and the lowest activity of AST and ALT were observed in the group fed 100 and 200 mg/kg diet, respectively. 3) In lipid metabolism enzymes, dietary silymarin supplementation significantly elevated the activities of LPL and total lipase TL in liver(P< 0.05), and the highest activity of lipase LPS was in 200 mg/kg diet, while it was significantly lower than the control group(P< 0.05). 4) Feed added silymarin significant increased glutathione peroxidase(GSH-PX) activity and decreased catalase(CAT) activity in liver(P< 0.05), and significantly reduced MDA content in liver(P< 0.05). 5) Liver slices of GIFT treated with dietary silymarin addition at 100 mg/kg showed few number of hepatocytes with empty vacuoles and less nuclear migration. In conclusion, appropriate dietary silymarin supplementation could promote growth performance, decrease muscle, whole body and hepatopancreas lipid contents, and regulate lipid metabolism enzymes and antioxidant ability in liver. Regarding the above results, the proper dose of silymarin in juvenile GIFT tilapia diet was suggested to be 100 mg/kg.3. An 9-week feeding experiment was performed to investigate the effects of dietary L-carnitine supplementation on growth performance, body composition, serum biochemical indices, hepatic lipid metabolism and antioxidant in juvenile GIFT strain(Genetically Improved Farmed Tilapia) of Nile tilapia Oreochromis niloticus(initial body weight: 8.21±0.33 g, means ± SD). Three practical diets were formulated with the incorporation of L-carnitine at the levels of 0(control), 150 and 300 mg/kg. Our results are as follows: Compared with the control group, dietary L-carnitine supplementation significantly increased weight gain rate(WGR) and specific growth rate(SGR)(P< 0.05), and significantly decreased hepatosomatic index(HSI) and viscerosomatic index(VSI)(P< 0.05). The highest WGR and SGR were observed for fish fed the diet containing 150mg/kg L-carnitine, and HSI and VSI were the lowest in this group. There were no significant differences in feed conversation rate(FCR) and survival rate(SR) among all the groups(P> 0.05). Feed added 150 or 300 mg/kg L-cranitine significantly increased the content of liver crude protein(P< 0.05), and crude lipid of liver that fed with 150 mg/kg L-carnitine was significantly lower than that of the control group. Dietary L-carnitine supplementation significantly decreased triglyceride in serum(P< 0.05), but there were no significant differences in total cholesterol(TCHO), high-density lipoprotein cholesterol(HDL-C) and low-density lipoprotein cholesterol(LDL-C)(P> 0.05). Dietary L-carntine supplementation significantly elevated the activities of lipoprotein lipase(LPL), hepatic lipase(HL), total lipase(TL) and lipase(LPS) in liver(P< 0.05). Feed added 150 or 300 mg/kg L-carnitine significantly increased catalase(CAT), glutathione peroxidase(GSH-PX) activities and significantly reduced malondialdehyde(MDA) content in liver(P< 0.05), the superoxide dismutase(SOD) and lysozyme(LZM) activities that fed with 300mg/kg L-carnitine were significantly higher than that of the control group. All the above results indicated that appropriate dietary L-carnitine supplementation could improve growth performance and antioxidant ability, promote lipid degradation and utilization. Regarding the effects on growth performance, the proper dose of L-carnitine in the juvenile GIFT diet was suggested to be 150 mg/kg.4. An 9-week feeding experiment was performed to investigate the effects of dietary glutathione(GSH) supplementation on growth performance, body composition, serum biochemical indicators and antioxidant ability in juvenile GIFT, Oreochromis niloticus(Initial body weight: 8.14±0.37 g). Three practical diets were formulated with incorporation of GSH at the levels of 0(control), 150 and 300 mg/kg. Our results are as follows: Compared with control group, feed added 300 mg/kg GSH significantly increased the WGR, and significantly decreased HSI for fish fed the diets containing 150 or 300 mg/kg GSH. There were no significantly differences of SGR, FCR, CF and SR among all of the groups(P> 0.05). Feed added 300 mg/kg GSH significantly increased the content of liver crude protein(P< 0.05), and crude lipid of liver that fed with 150 mg/kg GSH was significant lower than that of control group. Dietary 150 or 300 mg/kg GSH supplementation significantly increased CAT, GSH-PX and SOD activities in liver(P< 0.05). Dietary 300 mg/kg suppmentation significantly reduced MDA content, the LZM activities that fed with 150 mg/kg GSH were significantly higher than that of the control group. In conclusion, appropriate dietary GSH supplementation could promote growth performance and improve antioxidant ability in GIFT tilapia.