Effects of starvation on visceral weight and main biochemical composition of the muscle, liver and serum in the Japanese sea bass (Lateolabrax japonicus)
DU Zhen-Yu① LIU Yong-Jian ①* TIAN Li-Xia① CAO Jun-Ming② LIANG Gui-Ying① HE Jian-Guo① (①Institute of Economic Aquatic Animals, Sun Yan-Sen University, Guangzhou 510275, China) (②Guangdong Academy of Agriculture Sciences, Guangzhou 510640, China)
We investigated the effect of long-time starvation on the use of energy and symptoms of fat liver disease in the Japanese sea bass (Lateolabrax japonicus).Healthy Japanese sea bass(285 26±6 54 g)and Japanese sea bass with fat liver disease (464 71±54 22 g) were maintained in fresh water in outdoor concrete ponds (3 m×2 m×1 m) and starved for 9 weeks. Each treatment was replicated in triplicate. Water temperature in the experimental period was 22 93±2 15℃ and dissolved oxygen, pH and ammonia were 8 17±0 58 mg/L, 7 40±0 45 and 0 54±0 13 mg/L respectively. Samples were collected on weeks 0, 3, 5, 7 and 9 and the effects of starvation on gut weight, the nutritional content of muscle and liver, and some biochemical serum indices were observed. No fish died during the experiment. During starvation, the condition factor, gut ratio and intraperitoneal fat ratio decreased significantly (P0 05). The hepatosomatic index (HSI) in healthy Japanese sea bass was stable, but in sick Japanese sea bass decreased during the early period(from 1 09±0 14 to 0 65±0 03, P0 05)after which it remained stable(P0 05). The moisture content of muscle increased during starvation (healthy Japanese sea bass: from 78 30%±0 28% to 79 72%±0 22%; sick Japanese sea bass: from 76 95%±0 36% to 79 26%±0 11%, P0 05). The moisture content of the liver of healthy Japanese sea bass decreased from 69 62%±0 59% to 53 10%±2 27% (P0 05), but remained stable in sick Japanese sea bass(P0 05). The protein content of muscle significantly decreased during starvation (healthy Japanese sea bass: from 19 63%±0 22% to 18 54%±0 13%; sick Japanese sea bass: from 20 75%±0 15% to 18 90%±0 21%, P0 05), but fluctuated periodically in the liver(P0 05). The fat content of muscle decreased during the early period and then remained stable(P0 05). However, the fat content of the liver increased during starvation (P0 05)and this change was significant in healthy Japanese sea bass(from 9 84%±0 97% to 31 92%±3 49%,P0 05). A negative relationship was observed between moisture and fat content in the muscle and liver. The content of lipase (LIPA), triacylglycerol (TG), total cholesterol (TC), low density lipoprotein- cholesterol (LDL-C) and high density lipoprotein-cholesterol (HDL-C) in the serum fluctuated periodically during starvation. Wave-like curves were observed in healthy fish and hill-like curves in sick fish. The results show that the Japanese sea bass can endure starvation for a long time. There were some slight differences in the use of metabolic energy resources during starvation between healthy Japanese sea bass and those with fat liver disease. In healthy Japanese sea bass, intraperitoneal fat and muscle fat were metabolized first during the early period of starvation. Muscle protein was used as the main energy source during the whole starvation period. The content of protein and fat in the liver were relatively stable, so these tissues appear not to be a main energy source during starvation. Although the HSI of Japanese sea bass with fat liver disease decreased after 9 weeks starvation, the most important determinate index of fat liver disease, liver fat content, did not decrease. Thus the symptoms of fat liver disease in the Japanese sea bass were not alleviated by 9 weeks starvation.
【CateGory Index】： Q41