| Liza haematocheila belongs to Actinopterygii,Mugilidae,Liza,commonly known as meat stick in the north,also known as pointed head west.It is widely distributed in the Atlantic,Indian Ocean and the Pacific Ocean.In China,it is mainly distributed in the temperate and tropical waters from the Bohai Sea to the South China Sea.L.haematocheila is not only delicious and nutritious,but also has the advantages of wide salt,wide temperature and rapid growth.It is loved by the market and aquaculture industry and is one of the important economic fish in China’s offshore.The filter feeding and omnivorous feeding habits of L.haematocheila can play an important role in maintaining and optimizing the ecological environment of aquaculture waters.Therefore,many studies on the polyculture mode and proliferation and release of L.haematocheila have been done at home and abroad.At the same time,with the vigorous development of the domestic oyster and shrimp intensive aquaculture industry,the ecological and environmental problems brought by it have become increasingly prominent.In order to explore the feasibility and possible problems of releasing L.haematocheila in oyster culture area and polyculture of shrimp,this experiment studied the effects of long-term feeding of oyster sediment and shrimp pond sediment on the physiological and biochemical aspects of L.haematocheila from the perspective of feed.(1)In order to study the effects of oyster sediment(OY)and pond sediment(SH)on the growth of L.haematocheila,commercial feed(FE)was used as a reference.Through 42 days of breeding experiment,the organic matter content of three kinds of feeding food was detected,the feeding choice of L.haematocheila to three different foods was observed,and the changes of body length and weight of L.haematocheila during the experiment were measured.The results showed that the organic matter content in commercial feed was the highest,followed by pond sediment,and oyster sediment was the lowest.There was a significant difference in organic matter content among the three foods(P<0.05).The results of feeding selection of three kinds of food were positively correlated with the organic matter content of food.The specific growth rate,feed coefficient,condition factor and hepatosomatic index of FE group were significantly higher than those of the other two groups(P<0.05),but there was no significant difference in survival rate among the three experimental groups(P>0.05).The results showed that the L.haematocheila could feed on the sediments of oyster culture area and shrimp pond sediment,indicating that the L.haematocheila could be used for the restoration of culture area and pond sediment.However,due to the palatability of oyster sediment and pond sediment and the difference of nutritional components between them and commercial feed,only feeding these two foods may lead to the lack of nutrition or hunger of L.haematocheila,affecting its growth and fattening effect.(2)The contents of basic nutrients,fatty acids and amino acids in muscle of L.haematocheila were determined as the evaluation basis of the effects of three different feeds on body nutrition.The results showed that the crude fat content in the muscle of the oyster sediment group was lower than that of the other two groups,and there was no significant difference in moisture and ash content.From the perspective of fatty acid content,the total amount of saturated fatty acids in the muscle of the oyster sediment group and the shrimp pond sediment group was significantly lower than that of the compound feed group,and the total amount of saturated fatty acids in the two groups:the total amount of monounsaturated fatty acids:the total amount of polyunsaturated fatty acids.The ratio was 1.0:1.8:1.9,which was more inconsistent with the dietary structure standard than the 1.0:1.7:1.6 of the compound feed group,and the total amount of n-3 polyunsaturated fatty acids(DHA+EPA)was significantly better than the other two groups.From the perspective of total amino acids,the ratio of essential amino acids to total amino acids in the muscle of the three groups was EAA/TAA in the compound feed group(44%),oyster sediment group(43%)and shrimp pond sediment group(43%),and the ratio of essential amino acids to non-essential amino acids in the muscle of the three groups was EAA/NEAA in the compound feed group(73%),oyster sediment group(71%)and shrimp pond sediment group(70%).There was no significant difference and was in line with the WHO/FAO evaluation model.The results showed that different feeds had different influences on the component of the basic nutrition of the muscle of the L.haematocheila.The fatty acid structure of the muscle of the L.haematocheila fed on oyster sediment and shrimp pond sediment was poor,but the amino acid species were rich,and the EAA/TAA and EAA/NEAA indexes were normal,indicating that there was little effect on muscle protein composition.(3)The effects of different food feeding on the expression levels of two digestive enzymes(lipase LPS andα-amylase),three immune enzymes(superoxide dismutase SOD,catalase CAT and acid phosphatase ACP),Na~+-K~+ATPase(NKA)and immune-related genes(superoxide dismutase SOD,metallothionein MT,catalase CAT,heat shock protein HSP90 and Na~+-K~+ATPase)in the liver of L.haematocheila were studied.Liver samples were collected at the beginning of the experiment,the 14th day,the 28th day and the 42nd day,and the enzyme activity was determined.The results showed that the activities of two digestive enzymes in OY and SH groups increased first and then decreased during the experiment,and were significantly higher than those in FE group.The CAT enzyme activity in the immune enzymes of the two groups showed the same trend as the digestive enzyme,the SOD enzyme activity was higher than that of the FE group,and the ACP enzyme activity was always high,but it decreased slightly with the experiment.The NKA enzyme activity of the three experimental groups showed an upward trend,and there was no significant difference with the experiment.The expression levels of liver-related genes in OY were significantly higher than those in FE group,while only HSP90 and SOD genes in SH group were significantly higher than those in FE group,and the expression levels of other genes were higher than those in FE group,but there was no significant difference.The results showed that the OY group and SH group may be in a stress state for a long time during the experiment. |
