The inadequate nutrient content of pellet feeds widely used in recent years in China for grass carp forming led to lipid liver degeneration in the fish. The present studies show that the pathological features of lipid...The inadequate nutrient content of pellet feeds widely used in recent years in China for grass carp forming led to lipid liver degeneration in the fish. The present studies show that the pathological features of lipid liver disease are anaemia and hepatic ceroidosis. Other clinical features are: the ratio of liver to body weight exceeds 3% and lipid content exceeds 5%. Extreme infiltration of hepaiocytes by lipid results in the following deteriorative effects: swelling of the liver cells, increase of lipid droplets in the cytoplasm and dislocation of the nucleus, loss of cytoplasm staining affinity, and increased activities of GOT and GPT in serum. Lipid liver degeneration of grass carp can be divided into three stages: 1) deposition of liver lipid; 2) lipid infiltration of hepatic parenchyma; 3) atrophy of liver nucleus. The causes of lipid liver degeneration are complicated, but the main cause is assumed to be an imbalance of nutrients in daily feed and the lack of some lipotropic substances.展开更多
Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and l...Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and lowest at 5 fish per tank. The lower growth rate at the intermediate stocking density was associated with reduced feed efficiency, but there was no reduction in feed intake or digestibility. The results suggested increased metabolic cost caused by aggressive behaviour at intermediate stocking density, which can be suppressed by a further increase in density.展开更多
Hybrid tilapia weighing 7.71 g were reared in seawater at 24.0-29.0℃ for 8 weeks. The controls were fed to satiation twice a day throughout the experiment, whereas treatment groups were fed at 0.5%, 1.5% or 3.0% body...Hybrid tilapia weighing 7.71 g were reared in seawater at 24.0-29.0℃ for 8 weeks. The controls were fed to satiation twice a day throughout the experiment, whereas treatment groups were fed at 0.5%, 1.5% or 3.0% body weight per day for 4 weeks, and then to satiation for the remainder of the experiment. During the first 4-week period, there was a curvilinear relationship between growth rate and ration size. Fish fed 0.5% and 1.5% rations displayed compensatory growth response of 2 weeks duration during realimentation. The weight-adjusted growth rate of fish fed at 3% ration was not significantly different from that of the controls by the end of the experiment, when none of the treatment groups had caught up in body weight with the controls. Hyperphagia was observed for the first 2 weeks of realimenatation in fish previously fed at 3% ration, but persisted for the whole realimentation period in groups previously fed at 0.5% and 1.5% rations. None of the feed restricted groups showed improved digestibility, feed efficiency, or protein and energy retention efficiency.展开更多
文摘The inadequate nutrient content of pellet feeds widely used in recent years in China for grass carp forming led to lipid liver degeneration in the fish. The present studies show that the pathological features of lipid liver disease are anaemia and hepatic ceroidosis. Other clinical features are: the ratio of liver to body weight exceeds 3% and lipid content exceeds 5%. Extreme infiltration of hepaiocytes by lipid results in the following deteriorative effects: swelling of the liver cells, increase of lipid droplets in the cytoplasm and dislocation of the nucleus, loss of cytoplasm staining affinity, and increased activities of GOT and GPT in serum. Lipid liver degeneration of grass carp can be divided into three stages: 1) deposition of liver lipid; 2) lipid infiltration of hepatic parenchyma; 3) atrophy of liver nucleus. The causes of lipid liver degeneration are complicated, but the main cause is assumed to be an imbalance of nutrients in daily feed and the lack of some lipotropic substances.
文摘Hybrid tilapia were reared at densities of 1, 5 or 10 fish per tank for four weeks. Mortality was 0 at 1 and 10 fish per tank, but was 25% at 5 fish per tank. Specific growth rate was highest at 1 fish per tank, and lowest at 5 fish per tank. The lower growth rate at the intermediate stocking density was associated with reduced feed efficiency, but there was no reduction in feed intake or digestibility. The results suggested increased metabolic cost caused by aggressive behaviour at intermediate stocking density, which can be suppressed by a further increase in density.
基金Supported by the State Key Laboratory of Freshwater Ecology and Biotechnology of China and Shanghai Fisheries University (Grant No. 200015).
文摘Hybrid tilapia weighing 7.71 g were reared in seawater at 24.0-29.0℃ for 8 weeks. The controls were fed to satiation twice a day throughout the experiment, whereas treatment groups were fed at 0.5%, 1.5% or 3.0% body weight per day for 4 weeks, and then to satiation for the remainder of the experiment. During the first 4-week period, there was a curvilinear relationship between growth rate and ration size. Fish fed 0.5% and 1.5% rations displayed compensatory growth response of 2 weeks duration during realimentation. The weight-adjusted growth rate of fish fed at 3% ration was not significantly different from that of the controls by the end of the experiment, when none of the treatment groups had caught up in body weight with the controls. Hyperphagia was observed for the first 2 weeks of realimenatation in fish previously fed at 3% ration, but persisted for the whole realimentation period in groups previously fed at 0.5% and 1.5% rations. None of the feed restricted groups showed improved digestibility, feed efficiency, or protein and energy retention efficiency.
