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Nitrogen budget for a low‐salinity, zero‐water exchange culture system: II. Evaluation of isonitrogenous feeding of various dietary protein levels to Litopenaeus vannamei (Boone)
Author(s) -
PerezVelazquez Martin,
GonzálezFélix Mayra L,
GómezJiménez Silvia,
Davis Donald Allen,
MiramontesHiguera Noel
Publication year - 2008
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/j.1365-2109.2008.01971.x
Subject(s) - litopenaeus , shrimp , biology , zoology , salinity , nitrogen , ammonia , nitrite , food science , biochemistry , fishery , chemistry , ecology , nitrate , organic chemistry
This study evaluated the effects of isonitrogenous feeding (60 g dietary protein per kilogram of body weight per day) using experimental feeds with 25%, 30%, 35% and 40% protein on the nitrogen budget, ammonia efflux rate, growth and survival of juvenile Litopenaeus vannamei raised in a low‐salinity (4 g L −1 ) zero‐water exchange culture system for 4 weeks. No significant differences in weight gain or instantaneous growth rate were observed between the dietary treatments with 35% and 40% protein after 3 weeks of study, or between treatments with 25% and 30% protein after 4 weeks of study. High mortality rates were observed for the 35% and 40% protein treatments, probably associated with high nitrite levels (4.80 and 7.36 mg NO 2 ‐NL −1 respectively) in water. Among the various dietary treatments, 39–46.3% of feed nitrogen was converted to shrimp biomass, 32.8–38.0% and 14.4–39.9% remained within the system as organic and inorganic nitrogen, respectively, and 32.5–39.3% was unaccounted for. The results of the present study showed high nitrogen utilization efficiencies. However, as the nitrogen loading of the zero‐water exchange system increased, so did the nitrogen excretion of shrimp, causing a deteriorated general condition of the shrimp, demonstrated by the low ammonia efflux rates recorded at the end of the trial. This study confirms that low‐salinity closed systems are particularly susceptible to nitrogen loading. Thus, in these culture systems, low‐protein feeds may perform better as they provide more carbon for heterotrophic bacteria and less nitrogen to be degraded and transformed into nitrogenous wastes.