| Litopenaeus vannamei is also known as white shrimp of South America.Due to its good edible value and high economic value,it has become the shrimp with the highest yield in China.In recent years,with the increase in the breeding scale of L.vannamei,problems such as the reduction in quality and quantity of parental expansion have occurred.The enhanced nutrition of broodstock shrimp directly affects the sperm quality of male shrimp and the quality of larval rearing.The content of highly unsaturated fatty acids in feed affects the growth and development of broodstock and juvenile shrimp,while Schizochytrium sp.is rich in DHA and easy to industrialize.The advantages have attracted increasing attention from domestic and foreign scholars.Therefore,in this study,male shrimp L.vannamei was used as the test object.Three groups of experiments were carried out: adding 0%,3%,and 6% Schizochytrium sp.,and preparing the DHA content of 0.46%,1.20%,and 1.87%,respectively Feed(denoted as groups A,B and C).Male L.vannamei with an initial body weight of 37.4 ± 5.3g was fed.Through the detection of digestion,physiological and biochemical indicators,and sperm pod regeneration of L.vannamei,comprehensive evaluation of effects of Schizochytrium sp.on L.vannamei.The main test results were as follows:1、Effects of Schizochytrium sp.on digestive enzyme activities and gene expression levels of L.vannameiThere were no significant differences in the amylase activity of group A,B,and C between day10 and day 20;lipase activity: group B>group A>group C;Trypsin activity of group B was lower than that in group A significantly(P<0.05),and there was no significant difference in trypsin activity between groups C and A.The pepsin activity of group B and C was higher than that of group A significantly on day10(P<0.05),while no differences on day 20 among groups A,B and C,the relative expression levels of amylase and trypsin gene of group B on day10 and 20 were higher than those in groups A and C significantly(P<0.05),but there was no significant difference between groups A and C.The order of relative expression of lipase gene on day 10 was: group C>group B>group A,and the differences among the three groups were significant(P<0.05);the relative expression of lipase gene of group B on day 20 was higher than group A and group C significantly.while no significant difference between group C and group A.2、Effects of Schizochytrium sp.On Antioxidant Function of L.vannameiThere were no significant differences in CAT,T-AOC,and T-SOD activities of groups A,B,and C on day10;the LZM activity of group C was higher than that in groups A and B significantly(P<0.05).the CAT and T-SOD activities of group B and C groups on day 20 were higher than those of the group A significantly(P<0.05);compared with the group A,the T-AOC activities of group B and C were lower than those of group A significantly(P<0.05);The LZM activity of group C was significantly higher than that of groups A and B(P<0.05),and there was no significant difference in LZM activity between groups A and B.The relative expression of HSP70 gene in groups A,B and C was not significantly different on day10 and 20;the relative expression of CAT gene in group C on day 10 was significantly higher than that of groups A and B,and the relative expression of CAT gene in group A on day 20 was lower than the B and C groups significantly(P<0.05).3、Effects of Schizochytrium sp.on Lipid Metabolism of L.vannameiThe TC,TG,and LDL levels in the serum of group A,B and C showed no significant difference on day 10 and day 20;The HDL content in serum of group B and C was significantly higher than that of group A(P<0.05),but there was no significant difference between the two groups.the levels of LDL and HDL in hepatopancreas on day 10 and 20 were not significantly different among group A,B and C;the content of TC in the hepatopancreas of group C was significantly lower than that of group A and B(P<0.05);The order of TG content in hepatopancreas was: A>B>C.There were no significant differences in ALT and AST activities on day 10 and 20 among group A,B and C.The order of the FAS concentrations on day 10 was: A>C>B,while the order of CPT concentrations was: C>B>A.FAS concentrations of group B on day 20 were significantly lower than those in group A and C,and CPT concentrations of group A were significantly lower than those in group B and C(P<0.05).The relative expression levels of AMPK-α gene on day10 were not significantly different among group A,B,and C while the relative expression levels of AMPK-α gene in groups A and B on day 20 were significantly lower than those in group C(P<0.05).The relative expression of SREBP gene of group A on day 10 was significantly lower than those in group B and C(P<0.05).The order of relative expression of SREBP gene on day 20 was: A>B>C;the relative expression of FAS gene of group B on day 10 was significantly lower than that of group A and C(P<0.05),the relative expression of FAS gene of group A on day 20 was significantly higher than that of group B and C(P<0.05).4、Effects of Schizochytrium sp.on sperm pod regeneration of L.vannameiThe reproductive sperm pod quality,total sperm count,and live sperm percentage of male L.vannamei in groups B and C were higher than those in group A on day 10 and 20 after feeding experiment.The sperm pod quality and total sperm count in group B were significantly higher than those in group A(P<0.05);the quality of regenerated sperm pods of group A malesdecreased continuously with the culture time on day 10 and 20,and were significantly lower than the initial value(P<0.05);quality of sperm pods of group B males was significantly higher than the initial value on day 10 and 20(P<0.05),but there was no significant difference in the quality of sperm pods between day 10 and day 20.The quality of sperm pods of group C on day 10 was significantly higher than that on day 20 and initial value(P<0.05),but there was no difference between day 20 and the initial value;the sperm counts of male sprouts in group B on day10 were significantly higher than the initial values and day 20.The sperm counts of the regenerated sperm pods of the three groups on day 20 were significantly lower than the initial value(P<0.05);the percentages of live sperm of the regenerated sperm pods of group A,B,and C were not significant difference between day 10 and day 20. |
