| In this study,Channa argus was used as the test object to study the effects of zinc source and zinc level in dietary on the growth performance,feed utilization,deposition of zinc and immunity of Channa argus,to explore the nutritional requirements of Channa argus on different zinc sources in dietary,and the effect mechanism of zinc glycinate in feed on growth,antioxidant,immunity,fat metabolism,intestinal health and trace element deposition of Channa argus,and to reveal the physiological response mechanism of Channa argus to zinc deficiency and excess.Aimed to provide theoretical basis and production practice guidance for reduce the breeding feed cost of Channa argus,emission reduction,environmental protection,precision zinc nutrient supply and the maximum development of animal production potential.The results are as follows:(1)The nutritional requirements of Channa argus for different zinc sources in dietaryIn this study,in order to explore the suitable dietary zinc requirements of Channa argus for different zinc sources,0,20,40,60,80 and 100 mg/kg(marked by zinc)of zinc sulfate heptahydrate,zinc glycinate and nano-zinc oxide were added to the dietary with casein and gelatin as protein sources,respectively.Each group had three replicates and were grouped into the control group Zn11.4,zinc sulfate heptahydrate group SZn26.8,SZn47.9,SZn69.5,SZn88.3,SZn109.1,zinc glycinate group GZn26.5,GZn48.6,GZn69.9,GZn88.2,GZn109.3,nano-zinc oxide group NZn26.6,NZn48.2,NZn69.9,NZn88.4,NZn109.4.The breeding experiment lasted for 56 days,and the suitable demand for three zinc sources was evaluated by growth,feed utilization and immunization indicators.The results showed that:(1)The final body weight(FBW)and average weight gain rate(AWGR)of SZn69.5 group in zinc sulfate heptahydrate group were significantly higher than Zn11.4,SZn26.8 and SZn47.9 groups(P<0.05),the specific growth rate(SGR)was significantly higher than Zn11.4 and SZn26.8 groups(P<0.05),and the feed efficiency rate(FER)and protein efficiency rate(PER)in SZn69.5 group were significantly higher than Zn11.4,SZn26.8 and SZn47.9 groups(P<0.05),and serum LZM of Channa argus in SZn88.3 group was significantly higher than Zn11.4 group,SZn26.8 and SZn47.9 groups(P<0.05).(2)The FBW and SGR of GZn69.9 group in zinc glycinate group were significantly higher than Zn11.4 and GZn26.5 groups(P<0.05),and the AWGR was significantly higher than Zn11.4,GZn26.5 and GZn48.6 groups(P<0.05);the FER and PER of GZn69.9 group were significantly higher than Zn11.4 group.The serum LZM of Channa argus in GZn26.5 group(P<0.05)was significantly higher than GZn26.8 and GZn47.9 groups(P<0.05).(3)The FBW of NZn48.2 group in the nano-zinc oxide group was significantly higher than Zn11.4,NZn26.6 and NZn109.4 group(P<0.05),and the AWGR and SGR were significantly higher than Zn11.4 and NZn26.6 groups(P<0.05);the FER and PER of NZn48.2group were significantly higher than Zn11.4,NZn26.6 and NZn109.4 groups(P<0.05),and the serum LZM in NZn69.5 group had significantly higher than Zn11.4 and NZn26.8 groups(P<0.05).There were no significant differences in fatness,visceral body ratio(VSI)and hepatosomatic ratio(HSI)between the three zinc sources(P>0.05).According to the regression analysis of broken line model,the AWGR,PER and serum LZM were 68.34 mg/kg,64.41mg/kg and 87.22 mg/kg,respectively.The dietary zinc requirements with zinc glycinate as the zinc source were 53.21 mg/kg,50.07 mg/kg and 68.77 mg/kg,respectively.The dietary zinc requirements with nano-zinc oxide as the zinc source were 46.91 mg/kg,43.41 mg/kg and 51.55mg/kg,respectively.(2)Effects of different levels zinc glycinate added to dietary on growth,antioxidant and immunity,fat metabolism,intestinal health and trace element deposition of Channa argusIn order to evaluate the effects of different levels zinc glycinate added to dietary on growth,antioxidant and immunity,fat metabolism,intestinal health and trace element deposition of Channa argus,0,25,50,75,100,125,150,175 mg/kg(marked by zinc)were added to the dietary with casein and gelatin as protein sources.There were three replicates in each group,which were grouped as follows:control group Zn11.5,zinc glycinate group GZn34.6,GZn59.8,GZn85.1,GZn109.6,GZn134.3,GZn159.2 and GZn184.7 groups,and the breeding experiment lasted for 84 days.The results showed that the addition of zinc glycinate significantly increased FBW,AWGR,SGR,FER,and PER(P<0.05),which promoted its growth and feed utilization.The activities of SOD,Cu Zn SOD,CAT,GSH-Px and T-AOC in serum and liver were significantly increased(P<0.05),and the content of MDA was significantly reduced(P<0.05),and the expression of SOD,Cu Zn SOD,Nrf2 and GST in liver,spleen and head kidney was significantly up-regulated(P<0.05),improved the antioxidant capacity of Channa argus effectively.The contents of Ig M,C3 and C4 and LZM in serum were significantly increased(P<0.05),and the expression of IL-1β,IL-8,TNF-αand Nf-κB in liver,spleen and head kidney were significantly reduced(P<0.05),and the expression of IL-10 was significantly up-regulated(P<0.05),enhanced the non-specific immunity of Channa argus.Significantly increased the TC and TG content in serum and liver,and regulated fat deposition(P<0.05).The muscle thickness,fold height and fold width in the intestine of Channa argus were significantly increased(P<0.05),and the expression of Claudin-3 and ZO-1 was upregulated(P<0.05),improved intestinal morphology,significantly increased the activity of protease,amylase and lipase in the intestine of Channa argus(P<0.05),and effectively improved the digestion and absorption capacity of Channa argus for nutrients.The activities of SOD,Cu Zn SOD,CAT,GSH-Px and T-AOC in the intestine were significantly increased(P<0.05),the MDA content was significantly reduced(P<0.05),and the expression of SOD,Cu Zn SOD,Nrf2,GST and IL-10 was significantly up-regulated in the intestine(P<0.05).The expression of IL-1β,IL-8,TNF-αand Nf-κB was significantly down-regulated(P<0.05),improved intestinal antioxidant capacity and enhance non-specific immune function,effectively protecting intestinal health.With the increased of zinc glycinate level in dietary,the amount of zinc deposition in whole fish and vertebrae of Channa argus was significantly increased(P<0.05),while the amount of copper,iron and manganese deposits in whole fish and vertebrae were significantly decreased(P<0.05).In conclusion,the growth-promoting effect of zinc on Channa argus under the present experimental conditions was nano-zinc oxide > zinc glycinate > zinc sulfate heptahydrate.The addition of appropriate levels of zinc glycinate to the dietary significantly improved the growth and feed utilization of Channa argus,improved their antioxidant and immune capacity,regulated fat metabolism,protected intestinal health,and increased zinc deposition. |
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