| Trace elements,as prosthetic groups or activators of enzymes,play an important role in the physiological and biochemical processes in animals,or participate in the composition of certain special functional substances in the organism.The lack or imbalance of trace elements will affect the activities of certain enzymes,special functional substances and the function of organs and tissues,thereby hindering specific metabolic pathways and the physiological functions of the organism.Zinc is one of the most functional trace elements in the animal,the appropriate amount of zinc is beneficial to maintaining the normal growth performance,development,reproduction,immune response,and energy metabolism of aquatic animals.Therefore,it is particularly important to explore the optimal amount of dietary zinc in aquatic animals.With the development of the feed industry,the types of zinc additions have become more diversified,such as amino acid chelated zinc,and other new zinc sources,these zinc preparations have advantages like good palatability,easy absorption,better antiinterference and feeding effect,which have broad application prospects.In addition,with the increasing use of vegetable protein sources to replace fish meal,the influence of anti-nutritional factors on the full utilization of feed nutrients is also worthy of further investigation.The purpose of this study was to investigate the effects of zinc on juvenile Chinese mitten crab(Eriocheir sinensis).The main results and conclusions of this study are as follows:1 Effects of dietary zinc on growth,antioxidant capacity and nonspecific immunity in juvenile Chinese mitten crab Eriocheir sinensisZinc(Zn)is an essential trace mineral element in organisms and is involved in physiological processes.This study investigates the effects of dietary Zn on the growth,antioxidant capacity,nonspecific immunity and disease resistance of juvenile Chinese mitten crab Eriocheir sinensis.Zn was supplemented respectively at 0(control),25,50,100,200 and 400 mg/kg to the basal diet to form six diets as Zn0,Zn25,Zn50,Zn100,Zn200,and Zn400.Each diet was separately used to feed the crabs(0.40 ± 0.01 g)for 56 days.Zn deficiency led to a higher feed intake rate,a lower Zn content in the hepatopancreas and a lower nonspecific immune enzyme activity than other groups with Zn supplement.The final weight,weight gain rate,specific growth rate,Zn in the hepatopancreas,body crude protein,and the activities of serum alkaline phosphatase(AKP),acid phosphatase(ACP)and copper-zinc superoxidase(Cu Zn SOD)were significantly increased in the Zn100 group compared with other groups.Moreover,Zn accumulation in the hepatopancreas and body ash were significantly increased in the Zn200 group,and the antioxidant enzyme activities such as Cu Zn SOD and glutathione peroxidase(GSH-Px)in the hepatopancreas were significantly increased.In addition,the appropriate Zn activated the TLRs/NF-κB pathway after the lipopolysaccharide(LPS)injection,resulting in upregulation of the relative m RNA expression of antimicrobial peptide(ALFs).This study demonstrates that dietary Zn supplement can significantly improve growth performance,antioxidant capacity,nonspecific immunity and disease resistance of juvenile crabs.The regression analysis showed that the optimal dietary Zn level was 94.87 mg/kg for weight gain and 96.96 mg/kg for specific growth.2 Comparison of different dietary zinc sources on juvenile Chinese mitten crab,Eriocheir sinensisZinc(Zn)plays an essential role in various fundamental biological processes.However,there are certain differences in the utilization efficiency of different forms and dosage forms of zinc in animals.This study was conducted to explore the effects of four different Zn sources on growth performance,tissue Zn content,body composition,serum non-specific immunity and antioxidant status of juvenile Chinese mitten crab(Eriocheir sinensis).The juvenile crabs(3.09±0.01 g)were fed with four different diets which were a basic diet supplemented with 100 mg/kg of Zn sulfate(Zn SO4),tetrabasic Zn chloride(TBZC),Zn glycine(Zn-Gly)and hydroxy-methionine Zn(Zn-MHA)for 56 days.The results showed that: Compared with Zn SO4 group,the weight gain,specific growth rate,Zn content in the whole-body,hepatopancreas and muscle,and the activities of total superoxide dismutase(T-SOD),Cu Zn SOD and GSHPx were significantly increased in TBZC group.Compared with the Zn SO4 group,the Zn-Gly group and the Zn-MHA group have improved trends in the above aspects.The Zn-Gly can significantly increase the Zn content in the whole-body,hepatopancreas and serum,as well as the enzyme activities of serum AKP,ACP and SOD.The Zn-MHA can significantly increase the Zn content of whole-body,muscle and serum,and the enzyme activities of AKP,ACP,T-SOD and Cu Zn SOD in the serum.In this experiment,taking growth performance,antioxidant capacity,nonspecific immunity,and tissue Zn content as evaluation indicators,the comprehensive average relative bioavailability value of the four Zn sources were Zn-MHA,TBZC,Zn-Gly and Zn SO4 in order.The results would provide a theoretical basis for the appropriate option for dietary Zn sources.3 Effect of the zinc utilization in juvenile Chinese mitten crab Eriocheir sinensis fed diets containing phytic acidIn this experiment,a 3×2 two-factor experiment is designed in order to explore the effect of the Zn utilization in juvenile Chinese mitten crab fed diets containing phytic acid,Zn sulfate(Zn SO4·H2O)was used as the Zn source and phytic acid was added in the form of sodium phytate.The amount of Zn added was 0,100 and 200 mg/kg,and the phytic acid was 0 and 15 g/kg.Divide 720 juvenile crabs(3.11±0.01 g)into 6 groups,each with 4 repetitions and 30 juvenile crabs for each repetition.The test period is 56 days.The results were as follows:(1)The weight gain rate and specific growth rate of the 15 g/kg phytic acid supplemented group were significantly reduced on Zn0 groups.(2)The Zn content of whole body and hepatopancreas were increased significantly with the increase of Zn level,but that of 15 g/kg phytic acid supplemented group decreased significantly under the same Zn level.(3)There was the significant main interactive effect between dietary Zn level and phytic acid on the activities of amylase and lipase in the hepatopancreas,and amylase,lipase and trypsin in the intestine.The digestive enzyme activities of hepatopancreas were the highest in the 100 mg/kg Zn supplementation group,and it decreased significantly with the addition of 15 g/kg phytic acid.In the case of Zn deficiency,the addition of 15 g/kg phytic acid will significantly reduce the activities of digestive enzymes in the intestinal,but the effect will be significantly improved with zinc supplementation.(4)The total antioxidant capacity and superoxide dismutase activity of the intestine are similar to the trend of intestinal digestive enzymes.(5)15 g/kg phytic acid will increase the abundance of intestinal Vibrio in the case of Zn deficiency,and increase the relative abundance of Lactovum,Bacillus and Dysgonomonas when the amount of Zn is appropriate.This result showed that the interaction between zinc levels and phytic acid will affect the growth performance,zinc nutritional status,digestion capacity and intestinal flora of juvenile Chinese mitten crabs,which is reflected in the dietary zinc deficiency,15 g/kg phytic acid can cause growth inhibition,increased abundance of pathogenic bacteria,and reduced digestion in juvenile crabs.Supplementation of the 100 mg/kg zinc can significantly improve this negative effect,effectively increase the abundance of beneficial bacteria in the intestines and improve the digestive enzyme activities of intestinal. |
PDF Full Text Request