| The Xingkai Lake is a boundary lake between Chinese and Russian which is located in the southeast of Mishan city in Heilongjiang province. In recent years, The fishery resources of Xingkai Lake have been severely damaged with increasing the fishing intensity. In this study, the muscle composition(Nutritional component and amino acid) and digestive enzyme(protease,amylase and lipase) of the four Culters (Culter alburnus,Culter mongolicus,Culter dabryi and Cultrichthys erythropterus) in different seasons were studied,which could understand the nutritional values of the four culters and provide basic information to the relationship between the digestive enzyme activities and the utilization of nutrients, while this study also had some guidance on increasing the research in artificial breeding and releasing. The main results were as follows:One. The change study of digestive enzymes and amino acid in muscle of C.erythropterus in different seasonsThe change of digestive enzyme activity in hepatopancreas and intestinal and the change of amino acid in muscle were studied in C.erythropterus in different seasons. The results showed that protease, amylase and lipase activity were higher in the summer and autumn than the spring and winter, in which amylase activity in different season were significantly lower than the protease activity(P<0.05). The highest and lowest content of amino acid in muscle were glutamate and cystine, respectively. The content of essential amino acids of valine, methionine, isoleucine, phenylalanine and lysine in winter were lowest than other seasons(P<0.05). The content of non-essential amino acid did not have the same trend with the season change. The content of total amino acid and essential amino acid were higher in spring and summer than that in autumn and winter. The content of delicious amino acid was lowest in autumn, which indicated that the C.erythropterus in autumn tasted poor.Two. The study of digestive enzymes and composition of muscle of C.mongolicus in different seasonsThe change of digestive enzyme activity in different tissues of intestinal and hepatopancreas and the change of composition in muscle were studied in C.mongolicus in different seasons. The result showed that the protease activity of foregut, midgut and hindgut in C.mongolicus were highest in autumn and lowest in winter, with the change of seasons showed similar trends. The amylase activity of foregut and hepatopancreas had the same trend in different seasons and were highest in autumn. The amylase activity of midgut and hindgut in winter were highest and in spring were lowest ,respectively. The crude protein content in different seasons was from 15.06 to 19.63 present, and the highest was in autumn,while the crude fat was higher in winter and spring. The five essential amino acids (threonine, valine, methionine, lysine and tryptophan) in muscle were significantly lower than those in spring and summer(P<0.05), the non-essential amino acids did not have the same trend with the change of seasons. The total amino acid was highest in summer and lowest in autumn(P<0.05). The minimum content of essential amino acid was in winter. The content of delicious amino acid was lowest in autumn, which indicated that the muscle of C.mongolicus in autumn tasted poor.Three. The study of digestive enzymes and composition of muscle of C.dabryi in different seasonsThe change of digestive enzyme activity in intestinal and hepatopancreas and the change of composition in muscle were studied in C.dabryi in different seasons. The result showed that the protease activity in intestinal and hepatopancreas in C.dabryi were significantly lower in winter than in spring, summer and autumn(P<0.05). The amylase activity was significantly higher in autumn and winter than that in spring and summer(P<0.05). The lipase activity had the same change trend as follow: spring< summer<autumn<winter(P<0.05), which may be due to temperature and food abundance. The crude protein and crude fat were significantly higher in autumn and winter than those in spring and summer(P<0.05). There were six essential amino acid(valine, methionine, isoleucine, phenylalanine, histidine and arginine) with the same change trend for summer>autumn>winter>spring(P<0.05). The four non-essential amino acid(aspartic acid, glutamic acid, cystine and proline) and two essential amino acid(threonine and tryptophan) were highest in autumn, the content of total amino acid and essential amino acid were significantly higher in summer than those in spring, autumn and winter(P<0.05).Four. The study of the nutritive composition of C.alburnus in different seasons The nutritional component and amino acids change were studied in C.alburnus muscles in different seasons. The result showed that the order of the crude protein content of muscle changed with the seasons was: autumn>winter>spring>summer, the order of crude fat content was: spring>winter>summer>autumn. In different seasons, the content of seven essential amino acids(valine, methionine, isoleucine, leusine, phenylanine, lysine and tryptophan) and total essential amino acid were lower in winter than those in summer and autumn(P<0.05). The content of total amino acid and arginine and proline had the same change in different seasons, the order were: spring and summer>autumn>winter. The content of delicious amino acid was lowest in autumn, which indicated that the muscle of C.alburnus in autumn tasted poor.Five. Comparison of nutritive component among four wild culters The content of crude protein and fat in muscles(wet weight) of these four culters were 17.92%～19.86% and 0.12%～0.68% respectively. The content of crude protein in the muscle of C.erythropterus was significantly(P﹤0.05)higher than that of C.alburnus and C.dabryi, while closed to C.mongolicus(P﹥0.05); the content of crude fat was the lowest in these four culters. So it was conclude that there were some differences in nutritional components of culter in different species. The content of total amino acid in muscles (dry weight) from high to low were: C.erythropterus﹥C.dabryi ﹥C. alburnus﹥C.mongolicus.the order of total essential amino acid of exprimental population was: C.erythropterus﹥C.dabryi﹥C. mongolicus﹥C.alburnus, and for contents of delicious amino acld, it was C.alburnus﹥C.erythropterus﹥C.dabryi﹥C.mongolicus. The essential amino acids index (EAAI) was from 66.59 to 69.14,and the constitutional rate of the essential amino acids (EAA) met the Food and Agriculture Organization of the United Nations (FAO) / World Health Organization (WHO) Standard. the result demonstrated that all of four culters were high quality nutritional value fishes invovled in high protein content, low fat content and comprehensive amino acids. |
