Nitrogen excretion and absorption efficiencies of white steenbras,Lithognathus lithognathusCuvieSparidae, under experimental culture conditions
作者:
S A Harris,
T Probyn,
期刊:
Aquaculture Research
(WILEY Available online 1996)
卷期:
Volume 27,
issue 1
页码: 43-56
ISSN:1355-557X
年代: 1996
DOI:10.1111/j.1365-2109.1996.tb00965.x
出版商: Blackwell Publishing Ltd
数据来源: WILEY
摘要:
AbstractThe various components of the nitrogen budget of white steenbras,Lithognathus lithognathusCuvier (Sparidae), were determined under experimental culture conditions. A simple closed system respirometer was used where experiments were conducted to investigate faecal prodution, nitrogen excretion rates and absorption efficiencies at 16C and 20C. Faecal loss, as a percentage of the ingested nitrogen, amounted to 3.59%. Gross, carbon and nitrogen absorption efficiencies ranged from 8 6 to 9 8 % and were not significantly affected by fish size, ration size or temperature (P<0.05). Net protein utilization (NPU) and the biological value (BV) ranged from 78 to95%. Ammonia and urea constituted 77.93 and 10.07%, respectively, of the total exogenous nitrogen excretion, the balance being made up of other dissolved organic nitrogen (DON). Endogenous ammonia excretion rates were significantly greater in small fish compared to large fish (P<0.05). Total non‐faecal losses as a percentage of the ingested ration amounted to 21.86%. Fish size and ration size increased nitrogen excretion, but temperature had no effect. Maintenance rations were 7.55 mg g‐1dry weight day‐1(0.76%dry body weight) and 5.99 mgg‐1(0.60% dry body weight) for small and large fish, respectively. The high absorption efficiencies and high nitrogen indicated that white steenbras utilize the commercial trout pellet diet very effi
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