Open AccessEffect of Dietary Protein Concentration on Nitrogenous Waste in Intensively Fed Catfish Ponds
Author(s) -
Li Menghe,
Lovell Richard T.
Publication year - 1992
Publication title -
journal of the world aquaculture society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 60
eISSN - 1749-7345
pISSN - 0893-8849
DOI - 10.1111/j.1749-7345.1992.tb00759.x
Subject(s) - catfish , biology , zoology , weight gain , ammonia , nitrite , nitrogen , dietary protein , feed conversion ratio , protein efficiency ratio , food science , fish <actinopterygii> , body weight , biochemistry , chemistry , ecology , fishery , endocrinology , nitrate , organic chemistry
Channel catfish were fed five diets containing 24, 28, 32, 36 or 40% protein in intensively stocked earthen ponds over a 141 d growing season. Mean standing crop at harvest was 7,559 kg/ha, and maximum daily feed allowance was 105 kg/ha. Dietary protein concentration had a negative linear effect on weight gain. Total ammonia‐nitrogen (TAN) in pond water increased linearly as dietary protein concentration increased and was positively correlated with total protein fed. However, unionized ammonia‐nitrogen (NH 3 ‐N) was not influenced by dietary protein concentration. Dietary protein had a positive linear effect on nitrite‐nitrogen (NO 1 ‐ ‐ ‐N) concentration, which was positively correlated with total protein fed and TAN. There was no significant correlation between NO 2 ‐ ‐ ‐N and fish weight gain, although there was a significant positive correlation between NO 2 ‐ ‐ ‐N/Cl‐molar ratio in pond water and concentration of methemoglobin in the fish. Results from this study indicate that when the feeding rate is as high as 100 kg/ha/d, or 3,000 kg protein/ha/season, dietary protein concentrations of 36% and above can result in harmful concentrations of NO 2 ‐ ‐ ‐N when Cl concentration in the ponds is 2–3 mg/L. Although the NO 2 ‐ ‐ ‐N/Cl‐ ratio in the ponds increased to harmful levels with protein concentration of the diets, this might not be the major cause of the reduction in fish growth rate as dietary protein increased because the greatest difference in weight gain occurred at the lower protein concentrations and the greatest difference in NO 2 ‐ ‐ ‐N occurred at the higher dietary protein concentrations.