Ammonia and urea excretion rates of juvenile Australian short-finned eel ( Anguilla australis australis) as influenced by dietary protein level

• Published in: Aquaculture Vol. 194; no. 1; pp. 123 - 136
• Main Authors: Engin, K., Carter, C.G.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2001; Elsevier Science; Elsevier Sequoia S.A
• Subjects: Ammonia; Anguilla australis; Anguilla australis australis; Animal aquaculture; Animal productions; Australian short-finned eel; Biological and medical sciences; Excretion; Excretory system; Fish; Freshwater; Fundamental and applied biological sciences. Psychology; Nitrogen; Pisciculture; Protein intake; Proteins; Urea; Vertebrate aquaculture; Australian short-finned eel; Ammonia; Urea; Excretion; Protein intake; Anguilla australis australis; Variability; Fry; Feeding; Aquatic environment; Vertebrata; Diet; Pisces; Crude protein; Protein content; Aquaculture; Feed
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/S0044-8486(00)00506-8

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=0.022 x+0.058; n=12; r 2=0.88; P<0.001) and urea-nitrogen ( y=0.0044 x+0.426; n=12; r 2=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.