Growth, carcass composition and plasma growth hormone levels in cyclically fed rainbow trout

Growth, body composition and plasma growth hormone levels were recorded weekly for 24 weeks in rainbow trout Oncorhynchus mykiss . Underyearling rainbow trout were individually identified using coded tags and placed on either a cyclic feeding regime of 3 weeks of deprivation followed by 3 weeks of feeding or a daily feeding regime. No significant difference was found in standard length and mass among the cyclically fed and daily fed fish at the end of the experiment. For cyclically fed fish, the absolute specific growth rate and condition factor reached a maximum during the last week of refeeding. Cyclically fed fish had a significantly higher moisture and protein content and lower lipid levels relative to fish fed daily. Absolute mass and fat loss in the deprivation phase of the feeding cycle decreased in intensity with subsequent feeding cycles, indicating that the fish were acclimatizing to the feeding regime. It was proposed that this response was an adaptation against possible adverse effects in the adults ( e.g. locomotor performance, bone ossification rates, fat deposition rate, growth rate and age at sexual maturity). Plasma growth hormone concentrations were not affected by cyclic feeding indicating that variations in plasma growth hormone concentration are not the cause of compensatory growth in rainbow trout.     

Cyclic feeding and subsequent compensatory growth do not significantly impact standard metabolic rate or critical swimming speed in rainbow trout

Standard metabolic rate ( R _s) and critical swimming speed ( U _crit) were used to assess the aspects of physiological status (stamina) of rainbow trout Oncorhynchus mykiss . Fish were fed either 1·5% body mass daily, 1·5% body mass cyclically (3 weeks of food deprivation followed by 3 weeks of refeeding), a ration based on Stauffer's formula (a maximum temperature-specific ration level) daily or on Stauffer's ration cyclically for 18 weeks. It was hypothesized that if cyclic feeding had no impact on the status of the fish, R _s and U _crit would not cycle with the feeding regime. This hypothesis was supported. No significant difference was found between the mean mass and the fork length of the four groups at the end of the experiment ( P > 0·05). Feeding had no effect on changes in R _s among the four groups, which were significantly different throughout the experiment ( P ≤ 0·05). No significant difference in U _crit was found ( P > 0·05) until at week 12 between groups fed 1·5% body mass ration cyclically and Stauffer's ration daily ( P ≤ 0·05). For groups fed a 1·5% body mass ration cyclically and daily, significant differences occurred at week 15 ( P ≤ 0·05) but no significant difference was found by week 18 ( P > 0·05), suggesting that cyclic feeding does not affect the aspects of physiological status (stamina) of the fish.     

Compensatory growth in sub‐yearling Siberian sturgeon,Acipenser baerii Brandt, 1869: Effects of starvation and refeeding on growth,feed utilization and body composition

The capacity of sub‐yearling Siberian sturgeon (Acipenser baerii Brandt, 1869) (19.7 ± 0.8 g) to show compensatory growth was assessed for a 40‐day period for the effects of short‐term starvation and refeeding on growth, feeding performance and body composition. After acclimation, 25 experimental fish were randomly distributed among twelve 500‐L cylindrical fiberglass tanks with a flow‐through system. The fish were subjected to four different feeding regimes: control, which was fed four times daily to apparent satiation; T₁: four periods of 2 days starvation alternating with 8 days re‐feeding; T₂: two periods of 4 days starvation alternating with 16 days refeeding; T₃: an 8 days starvation period followed by 32 days refeeding. At the end of the experiment, the deprived fish attained body weights comparable to those attained by the control fish. There were no differences in growth and feeding performances between the deprived and the control fish. Total protein and lipid contents of the control fish were significantly higher than that of T₁ and T₂ fish at the end of the experiment (P < 0.05). A significant difference in the energy content was observed between T₂ and the control. Siberian sturgeon exhibited complete compensation, indicating a high ability of the deprived fish to grow sufficiently to fully compensate for weight loss during starvation. The results suggested that the feeding schedule involving starvation–refeeding cycles could be a promising feed management option for the culture of this species.     

Constraints of body size and swimming velocity on the ability of juvenile rainbow trout to endure periods without food

The hypothesis that body size and swimming velocity affect proximate body composition, wet mass and size‐selective mortality of fasted fish was evaluated using small (107 mm mean total length, L _T) and medium (168 mm mean L _T) juvenile rainbow trout Oncorhynchus mykiss that were sedentary or swimming ( c . 1 or 2 body length s⁻¹) and fasted for 147 days. The initial amount of energy reserves in the bodies of fish varied with L _T. Initially having less lipid mass and relatively higher mass‐specific metabolic rates caused small rainbow trout that were sedentary to die of starvation sooner and more frequently than medium‐length fish that were sedentary. Swimming at 2 body length s⁻¹ slightly increased the rate of lipid catabolism relative to 1 body length s⁻¹, but did not increase the occurrence of mortality among medium fish. Death from starvation occurred when fish had <3·2% lipid remaining in their bodies. Juvenile rainbow trout endured long periods without food, but their ability to resist death from starvation was limited by their length and initial lipid reserves.     

The effect of feed cycling and ration level on the compensatory growth response in rainbow trout, Oncorhynchus my kiss

Compensatory growth is the phase of rapid growth, greater than normal or control growth, which occurs upon adequate refeeding following a period of undernutrition. The effect of feed cycling periods (periods of starvation followed by periods of refeeding), ration level and repetitive feed cycles on the compensatory growth response in rainbow trout were evaluated in two experiments. A feeding cycle of 3 weeks starvation and 3 weeks feeding produced better results in terms of average percentage changes in weight and length, and in specific growth rate, than either 1 week and 1 week or 2 weeks and 2 weeks feed cycles. The fish on the 3 weeks starvation and 3 weeks feeding cycle did as well as, if not better than, the constantly fed controls over one or two complete cycles, though the controls were fed more than twice the amount of feed. Three ration levels were compared using a 3-week starvation and 3-week feeding period. The only effect of increasing ration level was to decrease conversion efficiency, indicating overfeeding. Carcass analysis of moisture, fat, protein and ash showed no significant differences between the controls and an experimental group on a 3 weeks starvation, 3 weeks feeding cycle after one complete cycle. Possible mechanisms underlying the compensatory growth response are discussed.     

Food restriction and refeeding in growing rats.

1. The interrelationship between food intake, body weight and oxygen consumption was analysed at 25 degrees C in growing rats. 3. The experiment was divided into two phases lasting four weeks each. During the first phase the animals were subjected to energy restriction and during the second phase they were allowed ad lib energy intake. Four groups of rats were studied: Control with ad lib food intake and three restricted groups R4, R5, and R6 which received during the first phase 4, 5, and 6 g per day of stock diet in a single meal. 3. The results showed a decrease in body weight and oxygen consumption during the restriction period and a recovering of the latter during the refeeding period, without body weight recovering. 4. It is concluded that an energy conservation mechanism is present during food restriction and for some time after refeeding.     

Growth performance and body composition in response to dietary protein and lipid levels in Nile tilapia (Oreochromis niloticus Linnaeus, 1758) subjected to normal and temporally restricted feeding regimes

A factorial experiment was designed to examine the effect on compensatory growth (CG) of Nile tilapia Oreochromis niloticus fed diets containing different protein and lipid levels under normal and temporally restricted feeding regimes. Four diets were formulated to contain either 30% or 36% crude protein, and 5% or 11% crude lipid. Triplicate replicates of each treatment were assigned to 24 150‐L tanks (20 fish/tank density). Fish (mean initial weight ± SD = 8.79 ± 0.34 g) were then fed either the normal feeding regime (thrice daily to apparent satiation) or the restricted regime (1 day feed deprivation followed by 3 days of feeding to apparent satiation) over a 44‐days study period. Fish receiving a diet under the restricted regime achieved weight gains (WG) comparable to fish consuming the diet containing 30% protein and 5% lipids under the normal feeding regime. Fish maintained on the restricted feeding regime exhibited reduced feed intake (FI), WG, feed efficiency ratio (FE), protein efficiency rate (PER) and hepatosomatic index versus fish on the normal feeding regime, except WG in fish fed the diet with 30% protein and 5% lipids. However, the resultant FI (85%~94%) was higher than the excepted 75% intake when fish were subjected to the restricted regime. Feeding 11% lipid diets led to improved FI, WG, FE, and PER compared to feeding the 5% lipid diets. Increased FI, WG, and FE, but reduced PER were observed in fish fed with 36% protein versus fish fed 30% protein. Fish receiving the 36% protein diets had lower whole‐body moisture and ash contents, but elevated whole‐body protein and lipid contents compared to those receiving the 30% protein diets. Whole‐body moisture contents were lower, but whole‐body protein, lipid and ash contents were higher in fish fed 11% lipid diets than in fish fed 5% lipid diets. There was an increase in whole‐body moisture content, but a decrease in protein and lipid content in response to the restricted feeding regime. Ash content was not affected by the feeding regime. The present study shows that Nile tilapia fed diets subjected to a restricted feeding regime exhibited growth comparable to those fed the diet at 30% protein and 5% lipid levels under a normal feeding regime. This positive effect was more pronounced in diets at a high protein level or in a combination of high protein and lipid levels.     

The effects of caloric restriction on the body composition and hibernation of the golden-mantled ground squirrel (Spermophilus lateralis)

In preparation for hibernation, golden-mantled ground squirrels (Spermophilus lateralis) must deposit sufficient amounts of lipid during the summer to survive winter hibernation. We conducted an experiment from May 1998 to February 1999 to examine the effects of caloric restriction on the body composition (lipid and fat-free mass) and hibernation of golden-mantled ground squirrels. Ground squirrels were either provided with food ad lib. (controls) or with only enough food to maintain a constant body mass throughout the experiment (calorically restricted). Changes in body composition were followed using total body electrical conductivity (TOBEC). Implanted data loggers that recorded body temperature were used to determine when ground squirrels entered their first torpor bout and the lengths of torpor bouts. Body composition did not change in the calorically restricted ground squirrels between May and September, while both lipid and fat-free mass increased in the controls. However, from September to February, calorically restricted ground squirrels lost only fat-free mass, not lipid mass, but controls lost both lipid and fat-free mass. Calorically restricted ground squirrels entered their first torpor bout about 4 wk after controls, but the torpor bout duration (or length) during hibernation did not differ between the two groups. These results show that ground squirrels maintain body composition during caloric restriction, and the limited quantities of stored lipid have an effect on when hibernation begins but not on torpor bout length.     

Energy Budget,Behavior and Leptin in Striped Hamsters Subjected to Food Restriction and Refeeding

Food restriction induces a loss of body mass that is often followed by rapid regaining of the lost weight when the restriction ends, consequently increasing a risk of development of obesity. To determine the physiological and behavioral mechanisms underlining the regaining, striped hamsters were restricted to 85% of initial food intake for 4 weeks and refed ad libitum for another 4 weeks. Changes in body mass, energy budget, activity, body composition and serum leptin level were measured. Body mass, body fat mass and serum leptin level significantly decreased in food-restricted hamsters, and increased when the restriction ended, showing a short “compensatory growth” rather than over-weight or obesity compared with ad libitum controls. During restriction, the time spent on activity increased significantly, which was opposite to the changes in serum leptin level. Food intake increased shortly during refeeding, which perhaps contributed to the rapid regaining of body mass. No correlation was observed between serum leptin and energy intake, while negative correlations were found in hamsters that were refed for 7 and 28 days. Exogenous leptin significantly decreased the time spent on activity during food restriction and attenuated the increase in food intake during refeeding. This suggests that low leptin in restricted animals may function as a starvation signal to induce an increase in activity behavior, and high leptin likely serves as a satiety signal to prevent activity during refeeding. Leptin may play a crucial role in controlling food intake when the restriction ends, and consequently preventing overweight.     

Effect of cellulase,phytase and pectinase supplementation on growth performance and nutrient digestibility of rainbow trout (Oncorhynchus mykiss,Walbaum 1792) fry fed diets containing canola meal

This experiment was conducted to evaluate the effects of supplementing exogenous enzymes on growth, feed conversion ratio (FCR) and apparent nutrient digestibility in rainbow trout (Oncorhynchus mykiss) fry diets containing 32% canola meal. Five experimental diets (including a control diet containing no enzymes) were prepared as isonitrogenous (44% crude protein) and isocaloric (4000 kcal DE kg¹). The four other diets contained either cellulase, phytase, pectinase or an enzyme mix (a mixture of cellulase, phytase and pectinase in the same ratio). The feeding trial was conducted in triplicate for 12 weeks in 15 tanks (100‐L). At the beginning of the experiment 20 rainbow trout fry (initial weight 1.23 g) were stocked into each tank. Mean water temperature in the rearing tanks was 11°C and water flow in each tank was 6 L min^?1. At the end of the experiment the growth parameters and FCR displayed no significant differences in enzyme supplementation (P > 0.05). In addition, no differences were observed in dry matter, protein, or lipid digestibility with enzyme supplementation (P > 0.05). The results of this study showed that the addition of pectinase, phytase, cellulase or an enzyme mix to a diet containing 32% canola meal had no effect on growth, feed efficiency or dry matter, protein, or lipid digestibility in rainbow trout fry.     

Compensatory growth in the rainbow trout, Salmo gairdneri Richardson

The effect of a period of starvation and subsequent refeeding on the weight and length of rainbow trout at different times of the year has been investigated. Fish that have been starved for 3 weeks and then fed for 3 weeks show a weight gain equivalent to or greater than that of fish fed normally for the 6 week period, in four out of the five periods studied. The study provided evidence of the adaptation of the fish to starvation followed by what may be termed compensatory growth once feeding was resumed. The length changes of the fish indicate that the weight gains were due to growth rather than increases in gut fat deposits or increased water uptake.     

Evaluation of safflower meal as a protein source in diets of rainbow trout [Oncorhynchus mykiss,Walbaum, 1792)]*

The effects of different levels of safflower meal (a residue of the plant oil extraction process) in diets of rainbow trout (Oncorhynchus mykiss) on growth performance, nutrient digestibility and body composition were investigated. Four different diets containing 0% (Control group), 10% (Diet 1), 15% (Diet 2) and 20% (Diet 3) safflower meal were formulated for the fish with a mean weight of 132.70 ± 0.75 g fed for 70 days. At the end of the experiment, there were no significant differences among dietary treatments for weight gain, specific growth rate and feed conversion ratio (P > 0.05). There were also no differences in the digestibility of crude protein and crude lipid between groups (P > 0.05). Supplementation of safflower meal in the diets also had no adverse effects on body composition. The results indicate that safflower meal is a promising feed ingredient and can be used up to a concentration of 20% in the rainbow trout diet with no adverse effects on growth performance, nutrient digestibility or body composition.     

Effect of diets containing sesame oil on growth and fatty acid composition of rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate effects of fish oil replacement by sesame oil in combination with other vegetable oils in diets with regard to growth performance, feed utilization, desaturation and elongation, whole fish and liver fatty acid profiles of juvenile rainbow trout. Sesame oil (SO) used in the feeds was a mixture of linseed (LO), sunflower (SFO) and fish oil (FO), whereas the control diet contained only FO. Duplicate groups of 60 rainbow trout (~7 g) held under similar culture conditions were fed 2% of their body weight per day for 75 days. At the end of feeding trials, there was no difference in feed utilization efficiency or growth performance between the control group and the groups with added sesame oil (P > 0.05). However, viscerosomatic and hepatosomatic index values were significantly higher (P < 0.05) in fish fed with FO30/SO35/SFO35 diets. Results showed that total body lipid levels of fish fed diets containing sunflower oil were higher than in the other experimental groups (P < 0.05). However, crude lipid levels were similar in fish fed the control diet and the diet with sesame oil (FO30/LO35/SO35), which is sunflower oil‐free. Crude lipid levels of fish livers were not influenced by the diets (P > 0.05). Diets with sesame oil increased desaturation and elongation of 18 : 3n‐3 towards n‐3 HUFA. The conclusion was that the diet addition of sesame oil in combination with other vegetable oils increased the nutritional quality of the whole fish and liver of juvenile rainbow trout, in particular the docosahexaenoic acid (DHA) level. Therefore, sesame oil may be of interest for use in aquaculture.     

The influence of previous feeding regime on the compensatory growth response of maturing and immature Arctic charr, Salvelinus alpinus

Alternating periods of food deprivation with those of unlimited provision of food depressed the growth of Arctic charr, Salvelinus alpinus , below that of controls. Fish that were deprived of food and then fed on alternate weeks (1:1) were larger than those that were exposed to periods of 1 5- or 3-week deprivation and feeding (1·5:1·5 or 3:3). On receiving excess food supplies following 24 weeks on the restricted feeding regimes the previously-restricted fish grew more rapidly than the controls. The greatest compensatory growth was displayed after the 3:3 regime, followed by the 1·5: 1·5 and then the 1:1 feeding regime. At the termination of the experiment there were no significant differences in body weight between fish fed according to the different regimes during the period that food restriction was imposed. Growth patterns of the immature males and females were similar, but mature males were significantly lighter than the immature fish by the end of the experiment. Both immature and maturing fish displayed a compensatory growth response on return to adequate feeding. Beginning food restriction in May did not influence the proportions of male fish ( c . 60%) which were mature in the autumn.     

Body mass and behavior in Swiss mice subjected to continuous or discontinuous food restriction and refeeding

Food restriction (FR) is hypothesized to decrease body fat content of an animal and thus prevent obesity. However, the response of energy budget to a continuous (CFR) or discontinuous FR (DFR) remains inconsistent. In the present study, effects of CFR or DFR and refeeding on energy budget and behavior were examined in male Swiss mice. CFR significantly decreased the energy expenditure associated with basal metabolic rate (BMR) and activity behavior, but not sufficiently to compensate for energy deficit and thus resulted in lower body mass and fat content. DFR mice had a significantly higher food intake on ad libitum days and showed increases in BMR and activity after 4 weeks’ DFR, which might resulted in lower body mass and less body fat than controls. After being refed ad libitum, both CFR and DFR mice had similar body mass, BMR, and behavioral patterns to controls but had 95% and 75% higher fat content. This suggested that not only CFR but also DFR would be a significant factor in the process of obesity for animals that were refed ad libitum. It also indicated that food restriction interrupted many times by periods of ad libitum feeding had the same long-term effects like continuous underfeeding.     

Effect of different level of roughage availability and contrast levels of concentrate supplementation on flavour of goat milk

Rancid and tart flavours are the most common off-flavours in Norwegian goat milk. In a feeding trial, we examined the effects of different levels of concentrate and of supplementary hay feeding on the occurrence of these off-flavours. Forty-eight experimental goats grazed cultivated pasture in the lowland during spring and autumn, and mountain pasture in summer. Twenty-four of the goats were fed 0.2 kg/day of concentrate (low concentrate, LC) and the remaining 24 goats 0.7 kg/day (high concentrate, HC). Twelve animals in LC and HC groups grazed freely, while the remaining goats in the two groups were given feeding challenges (limited periods of roughage restriction and ad libitum hay feeding). This was done to examine the effect of differing roughage availability on milk flavour. The animals fed low level of concentrate and with free grazing represented the control group. During the challenge periods, the goats were kept indoors and fed 0.2 kg hay/day for 2 days (roughage restriction) or hay according to appetite for 2 days (ad libitum feeding). At least 10 days of uninterrupted grazing were allowed between the challenges. Milk samples for sensory and chemical analysis were taken at the end of the challenge periods.The level of concentrate feeding did not influence the flavour of the milk when the goats were on lush spring pasture. However, the low level of concentrate feeding (LC) increased the frequency of off-flavour during the mountain and autumn experimental periods (P < 0.05).In the end of the mountain experimental period when the frequency of rancid/tart flavour increased in all groups, the sensory quality of milk produced by goats fed hay ad libitum (S1) had better taste ratings (P < 0.001) than milk from goats that were grazing. When the goats were given restricted amounts of hay, they adapted to the treatment by reducing their milk yield. In the spring and mountain experimental periods, restricted roughage feeding resulted in higher fat content and better taste ratings, especially in the group fed low level of concentrate (LC/S1). However, this connection was not clear in the autumn.Probably, the goats are able to handle a negative energy balance as long as mobilizable body reserves exist, but start to produce milk with lower dry matter content and higher frequencies of rancid/tart flavour when the body reserves are empty and the energy deficit is still pronounced.It is concluded that increasing the level of concentrate and feeding hay supplements will reduce the frequency of flavour defects at times when grazing is suboptimal or the pasture is of medium or low quality.     

Alterations in expression of genes associated with muscle metabolism and growth during nutritional restriction and refeeding in rainbow trout

Rainbow trout, as well as many other species of fish, demonstrate the ability to survive starvation for long periods of time. During starvation, growth rate is decreased and muscle exhibits signs of wasting. However, upon resumption of feeding, accelerated growth is often observed. Alterations in muscle metabolism occur during feed restriction and refeeding, although the ways in which these alterations affect the molecular pathways that control muscle growth have not been fully determined. To analyze changes in muscle metabolism and growth during starvation and refeeding, real-time PCR was used to test the expression of six metabolic-related genes and eight muscle-specific genes in rainbow trout white muscle prior to and after 30 days of starvation, and after 4 and 14 days of refeeding. The six metabolic-related genes chosen are indicative of specific metabolic pathways: glycolysis, glycogenesis, gluconeogenesis, the pentose phosphate pathway, and fatty acid formation. The eight muscle specific genes chosen are key components in muscle growth and structural integrity, i.e., MRFs, MEFs, myostatins, and myosin. Alterations in expression of the tested metabolic-related genes and muscle-specific genes suggest that during both starvation and refeeding, changes in specific metabolic pathways initiate shifts in muscle that result mainly in the modification of myotube hypertrophy. The expression levels of many of the metabolic-related genes were altered during the refeeding period compared to those observed before the starvation period began. However, the accelerated growth often observed during refeeding is likely driven by changes in normal muscle metabolism, and the altered expression observed here may be a demonstration of those changes.     

Changes in glucocorticoids, IGF-I and thyroid hormones as indicators of nutritional stress and subsequent refeeding in Steller sea lions (Eumetopias jubatus)

Physiological responses to changes in energy balance are tightly regulated by the endocrine system through glucocorticoids, IGF-I and thyroid hormones. Changes in these hormones were studied in eight captive female Steller sea lions that experienced changes in food intake, body mass, body composition, and blood metabolites during summer and winter. During a period of energy restriction, one group of sea lions was fed reduced amounts of Pacific herring and another was fed an isocaloric diet of walleye pollock, after which both groups returned to their pre-experimental diets of herring. Cortisol was negatively and IGF-I was positively associated with changes in body mass during periods of energy restriction (mass loss associated with increase in cortisol and decrease in IGF-I) and refeeding (body mass maintenance associated with stable hormone concentrations in summer and compensatory growth linked to decrease in cortisol and increase in IGF-I in winter). Cortisol and IGF-I were also correlated with changes in lipid and lean mass, respectively. Consequently, these two hormones likely make adequate biomarkers for nutritional stress in sea lions, and when combined provide indication of the energetic strategy (lipid vs lean mass catabolism) animals adopt to cope with changes in nutrient intake. Unlike type of diet fed to the sea lions, age of the animals also impacted hormonal responses, with younger animals showing more intense hormonal changes to nutritional stress. Thyroid hormones, however, were not linked to any physiological changes observed in this study.     

Dietary carotenoid pigment supplementation influences hepatic lipid and mucopolysaccharide levels in rainbow trout (Oncorhynchus mykiss)

We assessed the effects of dietary carotenoid pigment supplementation on liver histochemistry in the rainbow trout. One hundred and eight rainbow trout (mean mass 266 ± 10 g) were assigned to each of three replicate tanks for each of three dietary treatments; astaxanthin, canthaxanthin, or control at a target dietary inclusion of 100 mg/kg, by top-coating a pigment-free commercially extruded basal diet (Trouw Aquaculture, U.K.). Fish were fed for 3 weeks at a ration of 1.2% body mass/day, in a recirculating freshwater system maintained at 16 °C. Frozen liver sections were stained for total lipids, unsaturated lipids, glycogen, mucopolysaccharides, glycogen phosphorylase and aspartate aminotransferase. Relative amounts were measured quantitatively by image analysis. Carotenoid treatment significantly (P < 0.05) altered the total lipid profile and hepatic mucopolysaccharide contents of livers of rainbow trout. Results are discussed in relation to the catabolic potential of the liver in carotenoid pigment metabolism.