Ammonia and urea excretion rates of juvenile Australian short-finned eel (
Anguilla australis australis) as influenced by dietary protein level
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Engin, K and Carter, CG, Ammonia and urea excretion rates of juvenile Australian short-finned eel (
Anguilla australis australis) as influenced by dietary protein level, Aquaculture, 194, (1) pp. 123-136. ISSN 0044-8486 (2001) [Refereed Article]
This study aimed to determine excretion rates of ammonia and urea of Australian short-finned elvers as influenced by varying dietary crude protein intake. Elvers (2.3 ± 0.02 g) were fed diets containing dietary crude protein levels of 25% (P25), 35% (P35), 45% (P45) and 55% (P55) dry matter equivalent to 14.17, 19.24, 20.57 and 26.39 g CP/MJ, respectively (pairs of diets P25, P35 and P45, P55 were isoenergetic). Elvers were fed twice a day to a total of 6% BW/day and nitrogenous excretory products (ammonia- and urea-nitrogen) measured during the following 24 h and peak excretion rates occurred 4-8 h following both the morning and afternoon feed. Daily ammonia-nitrogen excretion was significantly (P < 0.05) higher on the P55 diet compared to the P35 and P45 diets. Increasing dietary protein intake resulted in increasing ammonia- (y = 0.022x + 0.058; n = 12; r2 = 0.88; P < 0.001) and urea-nitrogen (y = 0.0044x + 0.426; n = 12; r2 = 0.55; P < 0.01) excretion. The highest urea-nitrogen excretion as a percentage of consumed nitrogen was measured for fish fed the P25 diet (41.99 ± 2.62%) and compared with 30.29 (± 3.58%), 25.76 (± 1.41%) and 23.57 (± 1.54%) for diets P35, P45 and P55, respectively. The Australian short-finned eel appeared to be similar to other teleost and eel species in terms of the magnitude of ammonia-nitrogen excretion following feeding. However, higher rates of urea-nitrogen excretion indicates that urea is an important excretory end-product in this species. © 2001 Elsevier Science B.V.
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