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Nitrogen excretion and determination of nitrogen and energy budgets in rainbow trout ( Oncorhynchus mykiss R.) under different feeding regimes
Author(s) -
Weerd J.H. van,
Verástegui A. M.,
Tijssen P.A.T.
Publication year - 1995
Publication title -
journal of applied ichthyology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.392
H-Index - 62
eISSN - 1439-0426
pISSN - 0175-8659
DOI - 10.1111/j.1439-0426.1995.tb00034.x
Subject(s) - rainbow trout , excretion , zoology , biology , ammonia , postprandial , urea , nitrogen , kjeldahl method , fish <actinopterygii> , fishery , endocrinology , biochemistry , chemistry , organic chemistry , insulin
The postprandial excretion pattern of ammonia in dependence of feeding regime (fasting, 1 ×/day, 2 ×/day, 4 ×/day and continuous feeding), was determined in rainbow trout ( Oncorhynchus mykiss ), using continuous flow analysis. In fed fish ammonia peaked c. 7 h after the first meal with no differences in pattern between treatments. Fasting fish did not show a pattern. Overall production rates (NH 4 and NO 2 + NO 3 ) ranged from 0.29–0.31 g kg −1 BW/d in fed fish and were around 0.07 g kg −1 BW/d in fasting fish. Additionally determined total N (Kjeldahl) showed much higher values in fed fish (0.78–1.05 g kg −1 BW/d) but only slightly higher values in fasting fish (0.11 g kg −1 BW/d). Budgets of nitrogen (N) and energy (E) showed low recoveries ( c. 50% and between 50% and 70%, respectively). When correcting ammonia excretion (NH 4 and NO 2 + NO 3 ) using literature data on urea excretion of O. mykiss and assuming that total N partly stemmed from uneaten but undetected feed, both N and E budgets reached a recovery of around 100% in all four fed groups. Implications of this approach are discussed in the light of incomplete budgets as determined in earlier studies.