We evaluated the effect of ration level （RL） on the growth and energy budget of lenok Brachymystax lenok. Juvenile lenok （initial mean body weight 3.06±0.13 g） were fed for 21 d at five different ration level...We evaluated the effect of ration level （RL） on the growth and energy budget of lenok Brachymystax lenok. Juvenile lenok （initial mean body weight 3.06±0.13 g） were fed for 21 d at five different ration levels： starvation, 2%, 3%, 4% bwd （body weight per day, based on initial mean values）, and apparent satiation. Feed consumption, apparent digestibility, and growth were directly measured. Specific growth rates in terms of wet weight, dry weight, protein, and energy increased logarithmically with an increase in ration levels. The relationship between specific growth rate in terms of wet weight （SGRw, %/d） and RL （%） was characterized by a decelerating curve： SGRw=- 1.417＋3.1661n（RL＋ 1）. The apparent digestibility coefficients of energy exhibited a decreasing pattern with increasing ration level, and there was a significant difference among different RLs. Body composition was significantly affected by ration size. The relationship between feed efficiency rate in terms of energy （FERe） and RL was： FERe=- 14.167＋23.793RL-3.367（RL）2, and the maximum FERe was observed at a 3.53% ration. The maintenance requirement for energy of juvenile lenok was 105.39 kJ BW （kg）-0.80/d, the utilization efficiency of DE for growth was 0.496. The energy budget equation at satiation was： 100IE=29.03FE＋5.78（ZE＋UE）＋39.56 HE＋25.63 RE, where IE is feed energy, FE is fecal energy, ZE＋UE is excretory energy, HE is heat production, and RE is recovered energy. Our results suggest that the most suitable feeding rate for juvenile lenok aquaculture for wet weight growth is 2.89% bwd, whereas for energy growth, the suggested rate is 3.53% bwd at this growth stage.展开更多
Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to （1...Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to （1） determine if urea can function as a disturbance cue in juvenile convict cichlids and rainbow trout and （2） determine if the background level of urea influences the behavioral response to a subsequent pulse of urea （＇background noise＇ hypothesis）. In the first series of trials, juve- nile cichlids and trout were exposed to urea at varying concentrations （0 to 0.5 mg L-1 for cichlids and 0 to 1.0 mg L1 for trout）. Our results suggest that both cichilds and trout exhibited functionally similar responses to urea and conspecific disturbance cues and that increasing the concentration of urea results in an increase intensity of antipredator behaviour. In the second series of trials, we pre-exposed cichlids or trout to intermediate or high concentrations of urea （or a distilled water control） and then tested for the response to a second pulse of urea at at intermediate or high concentrations （versus a distilled water control）. Our results demon- strate that pre-exposure to urea reduces or eliminates the response to a second pulse of urea, supporting the background noise hy- pothesis. Together, our results suggest that pulses of urea, released by disturbed or stressed individuals, may function as an early warning signal in freshwater prey species展开更多
基金Supported by the Special Fund for Agro-Scientific Research in the Public Interest of China(No.201003055)the National Key Technology Research and Development Program of China(Nos.2012BAD25B10,2012BAD26B05)the Central-Level Non-Profit Scientific Research Institutes Special Funds of China(No.HSY201412)
文摘We evaluated the effect of ration level （RL） on the growth and energy budget of lenok Brachymystax lenok. Juvenile lenok （initial mean body weight 3.06±0.13 g） were fed for 21 d at five different ration levels： starvation, 2%, 3%, 4% bwd （body weight per day, based on initial mean values）, and apparent satiation. Feed consumption, apparent digestibility, and growth were directly measured. Specific growth rates in terms of wet weight, dry weight, protein, and energy increased logarithmically with an increase in ration levels. The relationship between specific growth rate in terms of wet weight （SGRw, %/d） and RL （%） was characterized by a decelerating curve： SGRw=- 1.417＋3.1661n（RL＋ 1）. The apparent digestibility coefficients of energy exhibited a decreasing pattern with increasing ration level, and there was a significant difference among different RLs. Body composition was significantly affected by ration size. The relationship between feed efficiency rate in terms of energy （FERe） and RL was： FERe=- 14.167＋23.793RL-3.367（RL）2, and the maximum FERe was observed at a 3.53% ration. The maintenance requirement for energy of juvenile lenok was 105.39 kJ BW （kg）-0.80/d, the utilization efficiency of DE for growth was 0.496. The energy budget equation at satiation was： 100IE=29.03FE＋5.78（ZE＋UE）＋39.56 HE＋25.63 RE, where IE is feed energy, FE is fecal energy, ZE＋UE is excretory energy, HE is heat production, and RE is recovered energy. Our results suggest that the most suitable feeding rate for juvenile lenok aquaculture for wet weight growth is 2.89% bwd, whereas for energy growth, the suggested rate is 3.53% bwd at this growth stage.
文摘Freshwater vertebrate and invertebrate prey species commonly rely on chemosensory information, including non-injury released disturbance cues, to assess local predation threats. We conducted laboratory studies to （1） determine if urea can function as a disturbance cue in juvenile convict cichlids and rainbow trout and （2） determine if the background level of urea influences the behavioral response to a subsequent pulse of urea （＇background noise＇ hypothesis）. In the first series of trials, juve- nile cichlids and trout were exposed to urea at varying concentrations （0 to 0.5 mg L-1 for cichlids and 0 to 1.0 mg L1 for trout）. Our results suggest that both cichilds and trout exhibited functionally similar responses to urea and conspecific disturbance cues and that increasing the concentration of urea results in an increase intensity of antipredator behaviour. In the second series of trials, we pre-exposed cichlids or trout to intermediate or high concentrations of urea （or a distilled water control） and then tested for the response to a second pulse of urea at at intermediate or high concentrations （versus a distilled water control）. Our results demon- strate that pre-exposure to urea reduces or eliminates the response to a second pulse of urea, supporting the background noise hy- pothesis. Together, our results suggest that pulses of urea, released by disturbed or stressed individuals, may function as an early warning signal in freshwater prey species
