The effects of dietary thiamin on oxidative damage and antioxidant defence of juvenile fish

The present study explored the effects of thiamin on antioxidant capacity of juvenile Jian carp (Cyprinus carpio var. Jian). In a 60-day feeding trial, a total of 1,050 juvenile Jian carp (8.20 ± 0.02 g) were fed graded levels of thiamin at 0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg thiamin kg^?1 diets. The results showed that malondialdehyde and protein carbonyl contents in serum, hepatopancreas, intestine and muscle were significantly decreased with increasing dietary thiamin levels (P < 0.05). Conversely, the anti-superoxide anion capacity and anti-hydroxyl radical capacity in serum, hepatopancreas, intestine and muscle were the lowest in fish fed the thiamin-unsupplemented diet. Meanwhile, the activities of catalase (CAT), glutathione peroxidase, glutathione S-transferase and glutathione reductase, and the contents of glutathione in serum, hepatopancreas, intestine and muscle were enhanced with increasing dietary thiamin levels (P < 0.05). Superoxide dismutase (SOD) activity in serum, hepatopancreas and intestine followed a similar trend as CAT (P < 0.05). However, SOD activity in muscle was not affected by dietary thiamin level (P > 0.05). The results indicated that thiamin could improve antioxidant defence and inhibit lipid peroxidation and protein oxidation of juvenile Jian carp.     

Effects of dietary histidine levels on growth performance,body composition and intestinal enzymes activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 1200 juvenile Jian carp (Cyprinus carpio var. Jian) (8.76 ± 0.02 g) were fed diets containing graded levels of histidine at 2.3 (unsupplemented control), 4.4, 6.3, 8.6, 10.8 and 12.7 g kg^?1 diet for 60 days to investigate the effects of histidine levels on growth performance, body composition, intestinal enzymes activities and microflora. Specific growth rate (SGR), feed efficiency, protein efficiency ratio, protein productive value, body protein content and lipid content of fish were lowest in fish fed the basal diet (P < 0.05). Activities of glutamate‐pyruvate transaminase in muscle and hepatopancreas, trypsin, chymotrypsin, amylase, lipase activities in intestine and hepatopancreas, and Na⁺, K⁺‐ATPase, creatine kinase, alkaline phosphatase, γ‐glutamyl transpeptidase activities in three intestinal segments were improved by dietary histidine (P < 0.05), whereas glutamate‐oxaloacetate transaminase activities and plasma ammonia content followed an opposite trend. The amounts of Lactobacillus, Escherichia coli and Aeromonas were significantly affected by dietary histidine levels (P < 0.05). These results suggested that histidine could improve growth and enhance intestinal enzymes activities of juvenile Jian carp. The dietary histidine requirement of juvenile Jian carp (8.76–68.02 g) based on SGR was 7.8 g kg^?1 diet or 2.38 g 100 g^?1 protein by quadratic regression analysis.     

Dietary phosphorus prevents oxidative damage and increases antioxidant enzyme activities in intestine and hepatopancreas of juvenile Jian carp

This study was conducted to investigate the effect of dietary phosphorus on the intestine and hepatopancreas antioxidant capacity of juvenile Jian carp (Cyprinus carpio var. Jian). Jian carp, with an average initial weight of 7.17 ± 0.01 g, were fed with diets containing graded concentrations of available phosphorus, namely 1.7 (control), 3.6, 5.5, 7.3, 9.2 and 11.0 g kg^?1 diet for 9 weeks. Results showed that, in intestine and hepatopancreas, content of malondialdehyde (MDA), protein carbonyl (PC) and glutathione (GSH), capacity of anti‐superoxide anion (ASA) and anti‐hydroxyl radical (AHR), and glutathione reductase (GR), catalase (CAT), glutathione S‐transferase (GST), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were significantly affected by dietary phosphorus levels (P < 0.05). Regression analysis showed that significant quadratic responses occurred in MDA content and ASA, GST, GPx and AHR activities in intestine, GSH content and CAT and SOD activities in hepatopancreas (P < 0.05). These results indicate that optimal level of dietary phosphorus prevented oxidative damage and increased antioxidant enzyme activities in the intestine and hepatopancreas of juvenile Jian carp. The phosphorus requirement estimated from MDA using quadratic regression analysis was 5.7 g kg^?1 diet.     

Antioxidant status of serum,muscle, intestine and hepatopancreas for fish fed graded levels of biotin

Lipid peroxidation, protein oxidation and antioxidant activities of muscle, intestine, hepatopancreas and serum in juvenile Jian carp (Cyprinus carpio var. Jian) were investigated after feeding graded levels of biotin (0.010, 0.028, 0.054, 0.151, 0.330, 1.540 and 2.680 mg kg^?1 diet) for 63 days. Both malondialdehyde and protein carbonyl content in all studied tissues and serum were the lowest in fish fed diets containing 0.151–0.330 mg biotin kg^?1 diet and then increased in fish fed the diet with 2.680 mg biotin kg^?1 diet (P < 0.05). Similarly, glutamate–oxaloacetate transaminase and glutamate–pyruvate transaminase activities in serum significantly decreased with biotin levels up to 0.151 mg kg^?1 diet (P < 0.05). Conversely, capacities of anti-hydroxyl radical (AHR) and anti-superoxide anion (ASA) in the detected tissues and serum significantly improved with biotin levels up to 0.054–1.540 mg kg^?1 diet and then decreased in 2.680 mg biotin kg^?1 diet group for muscle and intestinal AHR as well as hepatopancreas ASA (P < 0.05). Activities of superoxide dismutase in all studied tissues and serum significantly elevated with biotin levels up to 0.330 mg kg^?1 diet and then decreased when fish fed the diet with 2.680 mg biotin kg^?1 diet, except intestine (P < 0.05). Meanwhile, activities of catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase and total thiol content in all studied tissues and serum showed the upward trend with biotin supplementations (P < 0.05). These results indicated that biotin improved antioxidant status and depressed lipid peroxidation and protein oxidation in all studied tissues and serum.     

Effects of pyridoxine on antioxidative parameters in juvenile Jian carp (Cyprinus carpio var. Jian)

To investigate the effects of dietary pyridoxine (PN) on antioxidant status of fish in serum, intestine and trunk kidney, 1050 juvenile Jian carp (11.7 ± 0.1 g) were used for the experiment. The carp were divided into seven groups and fed diets containing graded levels of PN (0.20, 1.71, 3.23, 4.96, 6.32, 8.58 and 12.39 mg kg^?1 of diet) for 80 days. Results of the study showed that content of malondialdehyde in serum, intestine and kidney tissues was the highest when fed the diet containing 1.71 mg PN kg^?1 diet (P < 0.05). Meanwhile, the protein carbonyl content of intestine and kidney tissue showed a downward trend to a point (P < 0.05). Conversely, activities of superoxide dismutase, catalase, glutathione peroxidase (GSH‐Px), glutathione S‐transferase, glutathione reductase and glutathione (GSH) content in serum, intestine and kidney tissue were generally higher in PN‐supplemented diets than unsupplemented diet (P < 0.05). The present results indicated that the PN decreased lipid peroxidation and protein oxidation in fish, and partly because of its improved antioxidant enzymes activities and levels of GSH.     

Myo-inositol prevents oxidative damage, inhibits oxygen radical generation and increases antioxidant enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

This study was conducted to evaluate the effects of dietary myo -inositol (MI) on the antioxidant status of juvenile Jian carp ( Cyprinus carpio var. Jian). A total of 1050 Jian carp (22.28±0.07 g) were randomly distributed into seven groups of three replicates each, feeding diets containing graded levels of MI (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg kg⁻¹ diet) for 60 days. Results indicated that the malondialdehyde content was the lowest for fish fed diets containing ≥384.2 mg MI kg⁻¹, and the highest for fish fed the MI-unsupplemented basal diet ( P <0.05). The protein carbonyl content was decreased with increasing dietary MI levels up to 535.8 mg kg⁻¹ diet, and no differences were found with a further increase in the MI concentration. The anti-superoxide anion capacity (ASA) and anti-hydroxyl radical capacity (AHR) were increased with increasing MI levels up to 535.8 mg kg⁻¹ diet, and plateaued thereafter. The superoxide dismutase and glutathione- S -transferase activities showed the same tendency with the ASA capacity. Catalase, glutathione peroxidase and glutathione reducase activities were improved with increasing MI levels up to 838.8, 384.2 and 687.3 mg kg⁻¹ diet, respectively, and remained nearly constant thereafter. These results suggested that MI could inhibit oxygen radical generation, increase enzymatic antioxidant capacity and prevent oxidative damage of carp. Dietary MI requirements for ASA and AHR activities of juvenile Jian carp were 567.94 and 517.22 mg MI kg⁻¹ diet respectively.     

Effects of dietary vitamin K levels on growth performance,enzyme activities and antioxidant status in the hepatopancreas and intestine of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 1400 juvenile Jian carp (Cyprinus carpio var. Jian) (8.93 ± 0.03 g) were fed diets containing graded levels of vitamin K at 0.027 (basal diet), 1.52, 3.02, 4.51, 6.02 and 7.52 mg kg^?1 diet for 60 days to investigate the effects of vitamin K on growth, enzyme activities and antioxidant capacity in the hepatopancreas and intestine. Percentage weight gain (PWG), feed intake and feed efficiency of fish were improved by vitamin K. Activities of trypsin, chymotrypsin, amylase and lipase in the intestine and hepatopancreas and Na⁺, K⁺‐ATPase, creatine kinase, alkaline phosphatase and gamma‐glutamyl transpeptidase in the intestine were increased by vitamin K. Malondialdehyde and protein carbonyl contents in the hepatopancreas and intestine were decreased with vitamin K supplements. Certain level of vitamin K increased antihydroxyl radical, antisuperoxide anion, superoxide dismutase, catalase, glutathione‐S‐transferase, glutathione peroxidase and glutathione reductase activities and glutathione contents in the hepatopancreas and intestine. Intestinal Lactobacillus, E. coli and Aeromonas were changed with vitamin K supplements. Together, these results indicate that vitamin K improved fish growth, digestive and absorptive ability, and anti‐oxidant capacity. The dietary vitamin K requirement of juvenile Jian carp (8.93–73.7 g) based on PWG was 3.13 mg kg^?1 diet.     

Lipid peroxidation,protein oxidant and antioxidant status of muscle and serum for juvenile Jian carp (Cyprinus carpio var. Jian) fed grade levels of methionine hydroxy analogue

Lipid peroxidation, protein oxidation and antioxidant status of serum and muscle in juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of methionine hydroxy analogue (MHA: 0, 5.1, 7.6, 10.2, 12.7, 15.3 g kg^?1 diet) for 60 days were investigated. Both malondialdehyde and protein carbonyl content in serum and muscle decreased with increasing dietary MHA level up to 5.1–10.2 g kg^?1 diet (P < 0.05). Anti‐hydroxyl radical and activities of catalase, glutathione peroxidase and glutathione reductase in muscle and serum, as well as anti‐superoxide anion, superoxide dismutase activity and glutathione content in serum, increased with optimal MHA supplement (P < 0.05). Meanwhile, glutathione‐S‐transferase activity in serum showed a downward trend with dietary MHA up to 7.6 g kg^?1 diet (P < 0.05). These results indicated that MHA improved antioxidant status and depressed lipid and protein oxidation in serum and muscle.     

Influence of dietary zinc on lipid peroxidation,protein oxidation and antioxidant defence of juvenile Jian carp (Cyprinus carpio var. Jian)

This study was conducted to study the effects of dietary zinc on lipid peroxidation, protein oxidation and antioxidant defence of juvenile Jian carp (Cyprinus carpio var. Jian) by feeding fish with increasing levels of zinc (15.3, 26.9, 40.8, 58.2, 68.9 and 92.5 mg Zn kg^?1) for 6 weeks. Results indicated that malondialdehyde (MDA) content and protein carbonyls (PC) in serum were the highest in fish fed diet containing 15.3 mg zinc kg^?1 diet (P < 0.05). Serum antisuperoxide anion (ASA), superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), glutathione reductase (GR) activities and glutathione (GSH) content were improved with increasing dietary zinc levels up to 40.8 mg zinc kg^?1 diet (P < 0.05) and levelled off (P > 0.05). Serum antihydroxy radical (AHR), catalase (CAT) and glutathione‐S‐transferase (GST) activities followed the similar pattern to that observed in ASA. The MDA and PC levels, ASA, AHR, SOD, CAT, GPx, GR, GST activities and GSH content in intestine, hepatosomatic and muscle tissue followed the similar pattern to that observed in serum. The present results indicated that zinc decreased lipid peroxidation and protein oxidation and improved antioxidant defence in fish.     

Methionine hydroxy analogue prevents oxidative damage and improves antioxidant status of intestine and hepatopancreas for juvenile Jian carp (Cyprinus carpio var. Jian)

Oxidative damage and antioxidant status of intestine and hepatopancreas for juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of methionine hydroxy analogue (MHA: 0, 5.1, 7.6, 10.2, 12.7, 15.3 g kg^?1 diet) for 60 days were studied. Radical scavenging ability, antioxidant enzymes activities such as superoxide dismutase (SOD), catalase (CAT), glutathione‐S‐transferase (GST), glutathione peroxidase (GPX) and glutathione reducase (GR), as well as glutathione (GSH), protein carbonyl (PC) and malondialdehyde (MDA) contents were assayed in these tissues. Results indicated that anti‐superoxide anion capacity in intestine and anti‐hydroxyl radical capacity in hepatopancreas significantly improved with dietary MHA levels up to 7.6 and 10.2 g kg^?1 diet respectively, whereupon they decreased (P < 0.05). SOD, CAT, GST, GPX, GR activities in intestine and hepatopancreas, as well as GSH content in hepatopancreas significantly increased with optimal MHA levels which were in the range of 5.1–10.2 g kg^?1 diet, and thereafter decreased (P < 0.05). Meanwhile, MDA and PC contents in these tissues together with GOT and GPT activities in plasma significantly decreased with optimal MHA levels which were in the range of 5.1–7.6 g kg^?1 diet, and thereafter increased (P < 0.05). These results suggested that MHA improved antioxidant status and depressed lipid and protein oxidation in intestine and hepatopancreas.     

Dietary pyridoxine requirement of juvenile Jian carp (Cyprinus carpio var. Jian)

In a 80-day feeding trial, a total of 1050 juvenile Jian carp ( Cyprinus carpio var. Jian) with an average initial weight of 10.71 ± 0.05 g were fed semi-purified diets containing seven graded levels of pyridoxine (0.20, 1.71, 3.23, 4.96, 6.32, 8.58 and 12.39 mg pyridoxine kg⁻¹ diet). Results indicated that with increasing dietary pyridoxine levels up to 4.96 mg kg⁻¹ diet, percent weight gain (PWG) and specific growth rate (SGR) were improved, and no differences were found with further increase of pyridoxine levels. Feed intake also followed the similar pattern to that observed with PWG and SGR when dietary pyridoxine levels were ≤6.32 mg kg⁻¹ diet. But feed efficiency and protein efficiency ratio were not affected by pyridoxine levels. Crude protein of carcass, productive protein value and plasma ammonia concentration were improved with increasing dietary pyridoxine levels up to 4.96 mg kg⁻¹ diet. Amylase activities in the intestine were improved with increasing dietary pyridoxine levels up to 4.96 mg kg⁻¹ diet, but protease and lipase activities in the intestine were not affected by pyridoxine levels. Na⁺, K⁺-ATPase and Gamma-glutamyl transpeptidase activities in proximal intestine, mid intestine (MI) and distal intestine (DI) were lowest when fed the diet containing 1.71 mg pyridoxine kg⁻¹ diet. The alkaline phosphatase activities in MI and DI followed the same pattern. The dietary pyridoxine requirement of juvenile Jian carp based on PWG estimated by broken line model was 6.07 mg pyridoxine kg⁻¹ diet.     

Growth, digestive capacity and intestinal microflora of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary inositol

A 60‐day feeding trial was carried out with juvenile Jian carp (Cyprinus carpio var. Jian) to study the effects of myo‐inositol (MI) on the growth, digestive enzyme and intestinal microbial population. Diets with seven levels of inositol (163.5, 232.7, 384.2, 535.8, 687.3, 838.8 and 990.3 mg MI kg^?1 diet) were fed to Jian carp (initial weight 22.28±0.07 g). Per cent weight gain (PWG) was improved with increasing inositol levels up to 535.8 mg MI kg^?1 diet (P<0.05), and plateaued (P>0.05). The protein production value, lipid production value and ash production value were increased with increasing dietary inositol levels up to 384.2, 838.8 and 838.8 mg MI kg^?1 diet respectively (P<0.05). Although intestinal protein content and trypsin activity were not affected by inositol levels (P>0.05), chymotrypsin, lipase and amylase activities in intestine were the lowest for fish fed the MI‐unsupplemented diet (P<0.05). Alkaline phosphatase, Na⁺, K⁺‐ATPase, γ‐glutamyl transpeptidase and creatinkinase activities in the intestine were increased with an increase in the inositol levels up to 384.2–687.3 mg MI kg^?1 diet (P<0.05). Intestinal Aeromonas hydrophila and Escherichia coli decreased with an increase in the levels of dietary inositol up to 232.7 and 687.3 mg MI kg^?1 diet respectively (P<0.05), while Lactobacillus in the intestine increased with an increase in inositol levels up to 990.3 mg MI kg^?1 diet (P<0.05). In conclusion, inositol improved growth, digestive capacity and intestinal microbial population of juvenile Jian carp, and the dietary inositol requirement for PWG of juvenile Jian carp is 518.0 mg MI kg^?1 diet.     

Growth,body composition,intestinal enzyme activities and microflora of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary valine

This study investigated the effects of valine on growth, intestinal enzyme activities and microflora in juvenile Jian carp (Cyprinus carpio var. Jian). A total of 1200 fish with an average initial weight of 9.67 ± 0.03 g were fed diets containing 5.3 (unsupplemented control), 8.7, 11.8, 14.9, 18.7 and 20.1 g valine kg^?1 diet for 60 days. Results indicated that the specific growth rate, feed efficiency, body protein and lipid content of fish were significantly improved by the dietary valine (P < 0.05). The hepatopancreas weight and activities of trypsin, amylase, lipase, chymotrypsin, glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) took the similar trends. Similarly, the optimum levels of dietary valine induced increases in the intestinal length, weight, folds height and activities of alkaline phosphatase, gamma‐glutamyl transpeptidase and creatine kinase. In contrast, the trends of muscle GOT activity and plasma ammonia content were opposite. Intestinal Aeromonas, Escherichia coli, Lactobacillus and Bacillus were changed by dietary valine supplementations. The dietary valine requirement for Jian carp (9.67–76.4 g) based on SGR was 13.7 g valine kg^?1 diet (4.0 g valine 100 g^?1 CP). Together, these results indicated that valine improved fish growth, digestive and absorptive ability.     

Effect of methionine on intestinal enzymes activities, microflora and humoral immune of juvenile Jian carp (cyprinus carpio var. Jian)

An 8-week feeding experiment was conducted to determine the effect of dietary methionine supplementation on intestinal microflora and humoral immune of juvenile Jian carp (initial weight of 9.9 ± 0.0 g) reared in indoor flow-through and aerated aquaria. Eight amino acid test diets (350 g kg⁻¹ crude protein, CP), using fish meal, soybean-condensed protein and gelatin as intact protein sources supplemented with crystalline amino acids, were formulated to contain graded levels of methionine (0.6–22.0%) at a constant dietary cystine level of 3 g kg⁻¹. Each diet was randomly assigned to three aquaria. Growth performance and feed utilization were significantly influenced by the dietary methionine levels ( P  < 0.05). Maximum weight gain, feed intake occurred at 12 g kg⁻¹ dietary methionine ( P  < 0.05). Methionine supplementation improved hepatopancreas and intestine weight, hepatosomatic and intestine index, intestinal γ-glutamyltransferase and creatine kinase activity, Lactobacillus count, Bacillus count, lysozyme activities, lectin potency, sim-immunoglobulin M content, addiment C3,C4 contents and serum total iron-binding capacity and declined Escherichia coli and Aeromonas counts. Quadratic regression analysis of weight gain against dietary methionine levels indicated that the optimal dietary methionine requirement for maximum growth of juvenile Jian carp is 12 g kg⁻¹ of the dry diet in the presence of 3 g kg⁻¹ cystine.     

Effect of dietary iron levels on growth,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A 60‐day feeding trial was carried out to investigate the effect of iron on growth, body composition and digestive enzyme activities. Diets with seven levels of iron (53.9, 90.0, 115.6, 146.1, 176.0, 215.8 and 266.0 mg iron kg^?1 diet) were fed to Jian carp (initial weight 11.4 ± 0.0 g). Per cent weight gain (PWG), feed efficiency (FE) and protein efficiency ratio were the lowest in fish fed the basal diet (P < 0.05). Body protein content was increased with the increasing iron levels (P < 0.05), but moisture, lipid and ash of fish were not significantly affected by dietary iron levels (P > 0.05). Activities of trypsin, lipase, α‐amylase, Na⁺, K⁺‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase were improved with increasing dietary iron levels. Serum iron were significantly enhanced with dietary iron levels up to 146.1 mg iron kg^?1 diet, and plateaued. In conclusion, iron improved digestive enzyme activities of juvenile Jian carp and the dietary iron requirement for serum iron of juvenile Jian carp (11.4–64.0 g) was 147.4 mg iron kg^?1 diet with ferrous fumarate as the iron source.     

Effect of dietary pantothenic acid supplement on growth, body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A 9-week feeding trial was carried out with juvenile Jian carp to study the effect of dietary pantothenic acid (PA) on growth, body composition and intestinal enzyme activities. Semi-purified diets with seven levels (4.0, 15.5, 25.6, 36.1, 45.9, 56.1 and 65.9 mg PA kg⁻¹) of supplemental calcium d -pantothenate were fed to Jian carp (13.0 ± 0.0 g). PA improved specific growth rate (SGR), protein productive value (PPV), protein efficiency ratio (PER) and lipid production value (LPV) ( P <  0.05). Fish fed the control diet had significantly lower feed efficiency (FE) than that in any other group ( P <  0.05). Body protein content increased with increasing PA levels ( P <  0.05), but moisture, lipid and ash of fish carcasses were negatively related to the graded PA levels ( P <  0.05). Intestine protein content (IPC), hepatopancreas protein content (HPC) and activity of α-amylase, lipase, trypsin, Na⁺,K⁺-ATPase, alkaline phosphatase (AKP) and gamma-glutamyl transpeptidase (γ-GT) were all positively affected by the dietary PA levels ( P <  0.05), while intestine index (ISI) and hepatopancreas index (HSI) decreased with the increment of supplemental levels of PA ( P <  0.05). These results suggested that PA could enhance fish growth and intestinal enzyme activities. The dietary PA requirement of juvenile Jian carp, Cyprinus carpio var . Jian (13.0–73.0 g), for optimal growth estimated by the broken-line analysis was 23.0 mg PA kg⁻¹ diet.     

Growth,body composition,intestinal enzyme activities and microflora of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary phosphorus

A 9‐week feeding trial was carried out with juvenile Jian carp (Cyprinus carpio var. Jian) to study the effects of dietary phosphorus on growth, body composition, intestinal enzyme activities and microflora. Quadruple groups of juvenile Jian carp (7.17 ± 0.01 g) were fed practical diets containing available phosphorus 1.7 (unsupplemented control), 3.6, 5.5, 7.3, 9.2 and 11.0 g kg^?1 diet to satiation. Feed intake, specific growth ratio and feed efficiency were the lowest in fish fed the basal diet (P < 0.05). Body moisture, protein, lipid content and ash were all significantly affected by dietary available phosphorus levels (P < 0.05). Activities of trypsin, amylase, Na⁺, K⁺‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase were improved with increasing dietary phosphorus levels. Intestinal Aeromonas and Escherichia coli decreased with increasing dietary phosphorus up to 3.6 and 5.5 g kg^?1 diet respectively (P < 0.05), while Lactobacillus increased with the increasing dietary phosphorus up to 9.2 g kg^?1 diet (P < 0.05). These results suggested that phosphorus could enhance intestinal enzyme activities of juvenile Jian carp and the minimum dietary available phosphorus requirement for SGR of juvenile Jian carp (7.2–63.8 g) was 5.2 g kg^?1 diet.     

Growth,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian) fed graded levels of dietary zinc

A 6‐week trial was carried out with 900 juvenile Jian carp (Cyprinus carpio var. Jian) to investigate the effects of dietary zinc on growth, body composition and intestinal enzyme activities. Diets supplemented with increasing levels (15.3, 26.9, 40.8, 58.2, 68.9 and 92.5 mg Zn kg^?1) of zinc lactate were fed to Jian carp (mean initial weight 15.7 ± 0.01 g). Results indicated that per cent weight gain (PWG), feed efficiency (FE), protein efficiency ratio (PER) and lipid productive value (LPV) enhanced with dietary zinc levels up to 40.8 mg kg^?1 diet (P < 0.05), and plateaued thereafter (P > 0.05). Feed intake (FI) was similar to that observed for PWG. Intestosomatic index (ISI), relative gut length (RGL), hepatopancreas protein content (HPC), intestine protein content (IPC), trypsin, chymotrypsin, lipase, amylase, alkaline phosphatase (AKP), Na⁺, K⁺‐ATPase and γ‐glutamyl transpeptidase (γ‐GT) activities were all higher by dietary zinc supplementation than zinc un‐supplementation (P < 0.05). These results suggested that zinc could promote growth and increase nutrient deposition and intestinal enzyme activities. The dietary zinc requirements (use zinc lactate as zinc source) of juvenile Jian carp (15.7–42.2 g) based on PWG and serum zinc were 48.7 and 43.2 mg Zn kg^?1 diet, respectively.     

Effects of dietary thiamin supplement on growth,body composition and intestinal enzyme activities of juvenile Jian carp (Cyprinus carpio var. Jian)

A total of 1050 juvenile Jian carp (Cyprinus carpio var. Jian) (8.20 ± 0.02 g) were fed diets containing seven graded levels of thiamin (0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg kg^?1) for 60 days to investigate the effects of thiamin on growth, body composition and digestive enzyme activities. Percent weight gain (PWG), feed intake and feed efficiency (FE) were the lowest in fish fed the basal diet (P < 0.05). Protein productive value and lipid productive value increased with increasing dietary thiamin levels up to 1.06 and 0.79 mg kg^?1 diet, respectively (P < 0.05). Body protein and lipid increased with increasing dietary thiamin levels (P < 0.05), while moisture and ash of fish carcasses decreased with the increase in dietary thiamin supplementation (P < 0.05). Intestinal folds height had a similar trend to PWG (P < 0.05). Activities of α‐amylase, lipase, trypsin, Na⁺, K⁺‐ATPase, alkaline phosphatase and gamma‐glutamyl transpeptidase in intestine were all affected by the dietary thiamin (P < 0.05). In conclusion, thiamin could improve growth and intestinal enzyme activities of juvenile Jian carp. The dietary thiamin requirement of juvenile Jian carp (8.0–60.2 g) based on PWG was 1.02 mg kg^?1 diet.     

Effect of dietary thiamin supplement on immune responses and intestinal microflora in juvenile Jian carp (Cyprinus carpio var. Jian)

This study was to investigate the effect of dietary thiamin on the immune response and intestinal microflora in juvenile Jian carp (Cyprinus carpio var. Jian). Seven diets (0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg thiamin kg^?1) were fed to Jian carp (8.20 ± 0.02 g). At the end of feeding trial, red blood cell counts and white blood cell counts increased with increasing dietary thiamin levels up to 0.79 and 1.06 mg kg^?1 diet, respectively (P < 0.05); Lactobacillus counts in intestine increased gradually, and maximum values obtained when the thiamin level was at 0.79 mg kg^?1 diet (P < 0.05). After the feeding trial, fish were injected with Aeromonas hydrophila only one time on the first day of the challenge trial and fed the same diets as the growth trial for 17 days. The survival rate, leucocyte phagocytic activity, lectin potency, acid phosphatase activity, lysozyme activity, total iron‐binding capacity and immunoglobulin M content of fish after being injected with A. hydrophila were all improved with increasing dietary thiamin levels up to a point, respectively (P < 0.05). These results suggested that thiamin could improve immune response and the balance of intestinal microflora of juvenile Jian carp.