Assessment of nitrogen maintenance requirement in juvenile Black Porgy <Emphasis Type="Italic">Acanthopagrus schlegeli</Emphasis> |
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| Authors: | Qiuhua Zhu Guoying Qian Youling Gao Caisheng Wang |
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| Institution: | (1) College of Biological and Environmental Sciences, Zhejiang Wanli University, Ningbo, 315100, China |
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| Abstract: | Nitrogen balance method and nitrogen-free diet were used in this study to determine nitrogen maintenance requirement (NM)
and nitrogen maintenance requirement per unit metabolism body weight (NM′) of black porgy Acanthopagrus schlegeli. Fish with body weight (BW) of 50, 80, 120, 160 and 200 g were fed by the diets containing three graded levels of crude protein
(380, 420 and 460 g/kg). The results from nitrogen balance experiment showed that the amount of nitrogen deposition varied
from 0.15 to 0.31 mg/g BW per day, accounting for 12.2% to 21.1% of nitrogen intake. The amount of fecal nitrogen excretion
varied from 0.21 to 0.32 mg/g BW per day, accounting for 16.3% to 21.6% of nitrogen intake. The endogenous nitrogen excretion,
a main part of nitrogen consumption varied from 0.79 to 0.97 mg/g BW per day, accounting for 63.3 % to 68.0% of nitrogen intake.
Positive correlation was found between NM and body weight, while a negative correlation was found between NM of unit body
weight and the growth duration. No significant differences (p>0.05) were found in NM′ among different growth stages. The average of NM′ was 0.485 7mg/g per day. The results from nitrogen-free
diet experiment showed that a negative correlation between NM and feed intake of nitrogen-free diet. NM increased with the
decrease of feed intake of fish. The average of NM was 0.482 9 mg/g BW per day that was close to 0.483 8 mg/g BW obtained
from fish with 120 g BW in nitrogen balance experiment. The nitrogen balance method is recommended to be a better method for
determining NM in consideration of fish stress and result stability. This study also provides a calculated result of the protein
content in diets, which is necessary for maintaining fish body protein at different growth stages. The calculation was based
on the amount of nitrogen required for maintaining body protein per kg BW.
Supported by Scientific Research Project Grant (No.2004C100059) from the city government of Ningbo, China. |
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| Keywords: | Keyword" target="_blank">Keyword Acanthopagrus schlegeli nitrogen balance nitrogen-free diet nitrogen maintenance requirement protein contain levels |
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