Author
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Davis Jr, Kenneth |
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Gaylord, Thomas |
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Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only Publication Acceptance Date: 10/6/2004 Publication Date: 1/5/2005 Citation: Davis Jr, K.B., Gaylord, T.G. 2005. Metabolic consequences of feed deprivation in sunshine bass [abstract]. Book of Abstracts, Aquaculture America. p. 101. Interpretive Summary: Technical Abstract: The physiological consequences of feed deprivation and refeeding were studied on 11 month old sunshine bass (Morone chrysops X Morone saxatilis) in 60 l aquaria. Fish were held at 23 C and fed at about 1% of the body weight per day for one week and 2 tanks were sampled. An initial aquaria was sampled without disturbance and a second tank was exposed to a 15 min low water stress. Eight tanks were fed at 1% of the body weight for the rest of the experiment and ten tanks were not fed for three weeks. At the end of the third week two tanks which had not been fed for three weeks were fed with the same amount of feed that the fed group had been offered. Each week for four weeks a group of fed and non-fed fish were sampled before and after the low-water confinement stress. The fourth week included fish fed during the entire experiment, those not fed during the entire experiment, and those not fed for the first three weeks and then fed for the last week of the experiment. Fish were immersed in 3 mg/l metomidate hydrochloride and bled with heparinized syringes, hematocrit determined, and the plasma separated and stored frozen. Each fish was weighed and the liver and intraperitoneal body fat (IPF) dissected free, weighed, and expressed as the hepatosomatic index (HSI) or IPF respectively. The liver was stored frozen and the glycogen content determined. Plasma glucose concentration was determined by the glucose oxidase method and plasma concentration of cortisol and IGF-I was done by radioimmunoassay. The HSI and liver glycogen content of non-fed fish was significantly lower than fed fish by the end of the first week and remained lower for the rest of the experiment. However, fish starved for three weeks and fed for one week had completely regained both liver mass and glycogen content. Low water confinement stress had no effect on either liver weight or liver glycogen content. IPF was lower in non-fed fish than fed fish after two weeks of feed deprivation and remained lower for the rest of the experiment, further, IPF in fish fed for only the last week of the four weeks, remained significantly lower than fed fish. The stress had no effect on IPF. Plasma glucose was not consistently affected by feed deprivation. Low-water confinement stress resulted in significantly higher glucose concentrations than non-stressed fish in all trials with fed fish. However, the non-fed fish did not have higher glucose concentrations after the stress than in non-stressed fish. Plasma cortisol in non-stressed, non-fed fish was different from fed fish in only the fourth of the experiment where the fed fish cortisol concentration was higher than all the other non-stressed samples. Plasma cortisol was significantly higher in all stressed fish when compared to non-stressed fish. Plasma IGF-I concentrations was significantly lower in non-fed fish when compared to fed fish only after four weeks of feed deprivation and fish fed for only the last week of the four week experiment also had significantly lower IGF-I levels than fish fed daily throughout the experiment. In two of the four week samples 15 minute stress resulted in higher IGF-I levels than IGF-I levels in non-stressed, fed fish. Sunshine bass deplete their glycogen stores after one week of feed deprivation but restore glycogen levels quickly. IPF is used slowly and is restored slowly. Feed deprivation did not increase resting cortisol concentrations or reduce the cortisol response to stress. IGF-I concentrations were not affected until four weeks of feed deprivation. |
