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1.
Gastrointestinal and metabolic influences on short- and medium-term control of voluntary feed intake of European eel were investigated for groups of fish fed at different feeding schedules: 1 meal 2 days−1, 1 meal day−1, 2 meals day−1 and continuous feeding for 12 h and 24 h daily. For fish fed daily, the feeding schedule had no effect on feed intake, metabolism, growth, size variation and body composition. Only fish fed once every 2 days could not completely compensate by increasing their average meal size and showed a reduced feed intake, metabolism and growth. Stomach capacity did not limit meal size and feed intake as large differences in appetite were found for eels with empty stomachs. Feed intake was related to metabolism as the levels of O2 consumption and NH4 excretion just before the meal were correlated to average meal size, suggesting that rate (and duration) of metabolism is sensed and is providing information about the metabolic consequences of feed intake and feed processing. Meal size is based on the (expected) scope for metabolism and eels seem to strive to an average daily feed intake, associated with their developmental state (growth potential). Plasticity in this feed intake behaviour, expressed by individual variation in feed intake and day-to-day fluctuations in individual and group intake, is regarded as adaptive on different time scales.  相似文献   

2.
The effects of feeding frequency on food intake, weight change and relative proportions of the major body components were investigated at 10°C in a strain of hatchery-reared rainbow trout. Feeding frequencies were from one meal every second day to six meals per day, within the range common to current piscicultural techniques. Fish were fed a dry, pelleted diet either to satiation at each meal, or in restricted total daily amounts based on a percentage of their wet body weight. All fish were forced to swim at a constant speed of approximately one body length per second to minimize variability in growth and body composition.Maximum daily food intake occurred with just two feedings to satiation per day. Growth closely paralleled food intake. Neither specific growth rate nor whole body levels of moisture, lipid or protein were affected significantly by differences in feeding frequency. A trend towards increased body fat with more frequent feeding was observed among fish fed to satiation at each meal; this was believed to be the result of a somewhat higher total food intake than among less frequently fed fish. Fish fed a restricted daily ration divided into a number of meals exhibited smaller differences in lipid content.The general lack of response to feeding frequency was attributed primarily to the low metabolic rate of trout and to the characteristically slow rate of food passage in the digestive tract.  相似文献   

3.
Studies on the effects of feeding frequency on the growth of young estuary groupers (Epinephelus tauvina) with initial size ranging from 16.2 to 16.9 cm in total length were conducted in floating net-cages. Seven feeding frequencies in the order of one feeding in 5 days, 4 days, 3 days, 2 days, 1 day, two feedings daily and three feedings daily were studied. Optimal growth and good food conversion ratio as well as higher survival rate were obtained in groups fed to satiation with one feeding in 2 days. Weight gains were substantially reduced in groups fed to satiation with one feeding in 5, 4 or 3 days and were not enhanced when the feeding frequencies were increased to two or three feedings daily. The fact that food conversion ratios were similar in fish fed to satiation with one feeding in 5, 4, 3 and 2 days suggests food intake to be important as a growth limiting factor. Total food intake per feeding was appreciably higher in fish fed once in 2 days. The intake of food was found to be closely related to the amount of food remaining in the stomach, intake being maximal when the stomach was empty. The food deprivation time in estuary groupers was found to be about 36 hours at which over 95% of the food was digested and less than 0.5% body weight of food remained in the stomach. Hence, feeding the fish at 48-hour intervals, i.e. once in 2 days, greatly enhanced maximum intake and efficient utilization of the food.  相似文献   

4.
Abstract. The spatial distribution of Atlantic salmon, Salmo salar L., in sea cages was observed by echo integration, which measured fish density at seven in depth intervals. At start of feeding the fish swam towards the surface and into the centre of the cage with a subsequent movement downwards and towards the periphery as hunger was reduced. These changes were more rapid at high than at low feeding intensities. The downward migration during feeding was primarily observed as a reduction in fish density in the 0–1 m depth layer and an increase in the 2–3 m depth layer. For a given feeding intensity, the change in fish density in these depth layers was largely explained by time from the start of feeding and initial hunger level, measured as food intake to satiation. The feeding regime also influenced vertical distribution outside feeding periods. Fish that were fed at low intensity swam generally closer to the surface, and this tendency was even stronger when a restricted food ration kept hunger level constantly high. While fish density peaked at a single depth interval at full ration, a bimodal vertical distribution was observed at restricted ration, suggesting that different subgroups of fish had different feeding motivations. The results suggest that the vertical distribution of salmon in sea cages is based on a trade-off between attraction to food and avoidance of the surface. This tendency has been exploited in a new method of demand feeding in commercial farming of Atlantic salmon.  相似文献   

5.
In salmonids, growth hormone (GH) stimulates growth, appetite and the ability to compete for food. This study tested the hypothesis that increased GH levels in GH-transgenic coho salmon Oncorhynchus kisutch (Walbaum) increase competitive ability through higher feeding motivation. The transgenic strain of salmon used contained a gene construct consisting of the sockeye metallothionein-B promoter fused to the type 1 growth gene coding region. The transgenic animals (mean size = 250 g) were F1 individuals. In six consecutive feeding trials, the intake of contested food pellets by size-matched pairs consisting of one control (1 year older non-transgenic coho salmon) and one GH-transgenic coho salmon was compared. Pellets were provided sequentially until neither fish took three consecutive pellets; the identity of the fish taking each pellet was noted. Calculated on the three first pellets offered at each feeding trial, the transgenic coho salmon consumed 2.5 times more contested pellets than the controls, supporting the hypothesis that GH transgenesis increases the ability to compete for food. Overall, the transgenic fish consumed 2.9 times more pellets that the non-transgenic controls, indicating a high feeding motivation of the transgenic fish throughout the feeding trials. It appears that GH transgenesis and GH treatments can induce similar changes in the feeding behaviour of salmonids. Depending on how transgenic and wild individuals differ in other fitness-related characters, escaped GH transgenic fish may compete successfully with native fish in the wild.  相似文献   

6.
Growth, nutrient utilisation and gastrointestinal evacuation time using different fish meal particle sizes and dietary protein concentration was examined in Atlantic salmon. Salmon were given micro, standard or coarse grounded fish meals at two dietary protein concentrations (30 or 45%) in isolipid diets. Gastric evacuation time was influenced by fish meal particle size. Coarse ground fish meal gave a slower gastric evacuation time compared to finer ground fish meal. Specific growth rate was not influenced by the protein concentration, but there was an adverse effect of coarse ground particles. This effect may be explained by the reduced feed intake of fish fed diets containing coarse ground fish meal. Feed conversion ratio (FCR) or energy conversion ratio (ECR) was reduced with increasing dietary protein concentration. This effect was mainly caused by different energy levels in the diets and not protein/carbohydrate levels. Standard coarse fish meal gave a reduction in ECR, but there was no effect of fish meal particle size on FCR. A protein sparing effect of starch was demonstrated. Productive protein value (PPV) and productive energy value (PEV) was not affected by dietary protein concentration or fish meal particle size. Dietary protein concentration had no effect on nitrogen or fat digestibility but there was a reduction in fat digestibility when coarse ground fishmeal was used in the diets. There were only minor effects on the dressing out percentage, condition factor and fat in cutlet.  相似文献   

7.
The effects of feeding time and frequency on the growth, feed utilization and survival of Clarias gariepinus (Burchell 1822; family Clariidae) fingerlings were evaluated in a 25-day study. Groups of African catfish with an initial individual weight of 0.98 ± 0.02 g were offered feeds continuously for 24 h, or during the day or night at different time intervals, with varying meal size. The growth rate was significantly affected by meal times. Widely practised day time feeding with three equal size meals a day gave the lowest growth and highest food wastage. The growth rates of fish fed continuously or during night time following their feed demand were significantly higher with lowest food conversion ratios and food wastage.  相似文献   

8.
In a 6-week feeding experiment, chum salmon, Oncorhynchus keta, swim-up fry, were fed fish meal diets supplemented with silkworm pupae powder (5%), dried beef liver (5%), krill meal (5%) or earthworm powder (5%) at the expense of fish meal, or substituting glucose (13%) for dextrin. Fish fed the diet with earthworm powder showed the best growth performance (675% weight gain in 6 weeks) and feed efficiency (117%). The growth rate and feed efficiency of the krill meal group were also significantly better than those of the control group (without supplement or substitution). Substitution of glucose and supplementation of silkworm pupae or beef liver failed to improve the growth rate, but significantly improved feed efficiency. Food consumption of fish fed the diet supplemented with earthworms was lowest, and none of the dietary treatments appreciably increased food intake of the fish over that of the control group. The dietary group receiving earthworm powder also showed significantly higher body fat content than the remaining dietary groups. No significant differences were noted in body protein and ash contents among all dietary treatments.  相似文献   

9.
The effects of different feeding methods on growth and slaughter traits of Atlantic salmon, Salmo salar, have been examined. Swimming activity associated with feeding was greatest amongst fish fed using automatic feeders, intermediate amongst those fed predetermined rations by hand, and least in groups of fish fed to satiation twice per day. Fish fed to satiation ate more and grew faster than did those provided with rations predicted to support high rates of growth, but the fish fed to satiation had higher feed:gain ratios than those given predetermined rations as two meals per day. The muscle tissues of the fish fed to satiation had higher lipid (%) and lower moisture (%) contents than did those of the fish fed the predetermined rations, but differences in muscle composition could be accounted for by differences in the size of the fish. Lipid was positively, and moisture negatively, correlated with fish size, whereas per cent protein and dress-out losses were little influenced by fish size and feeding regime. The fish fed to satiation were slightly heavier for a given length than those in the other groups. There was, however, no evidence that the largest fish had the highest condition factor, nor could condition factor be used to predict per cent lipid in the muscle tissue. Size variation increased in all groups of fish, and this was, in part, due to the cessation of growth of maturing individuals. Size variation was, however, most marked in the groups fed using automatic feeders, suggesting that interindividual competition for food was greatest amongst these fish.  相似文献   

10.
A 6‐wk feeding trial was conducted to evaluate the effects of different dietary lipid levels and feeding frequencies on the growth performance, feed utilization, and body composition of juvenile spotted seabass, Lateolabrax maculatus. Two experimental diets were prepared with two different dietary lipid contents, low lipid (7%; LL) and high lipid (14%; HL). Each diet was fed to triplicate groups of fish (5.5 ± 0.01 g) to apparent satiation at three meals per day, two meals per day, one meal per day, and one meal every 2 d, respectively, for 6 wk. Fish growth performance in terms of weight gain (WG) and specific growth rate (SGR) was significantly affected by frequency of feeding, with increasing values as feeding frequency increased up to twice daily, regardless of dietary lipid content. In addition, fish fed the diet with the HL level (14%) showed significantly higher WG and SGR than those fed the LL diet (7%) at all the feeding frequencies tested. Feed efficiency (FE) and protein efficiency ratio (PER) were affected by both dietary lipid level and feeding frequency. FE and PER values were significantly higher in fish fed the HL diet and/or when fish were fed twice or thrice a day. However, daily feed intake and daily energy intake were significantly affected only by feeding frequency and were significantly reduced when the fish were fed only once every 2 d compared with those fed more frequently. Whole‐body moisture content of fish tended to decrease with increasing dietary lipid level and frequency of feeding. In contrast, whole‐body lipid content increased in fish as dietary lipid level and feeding frequency increased. Consequently, we can conclude that feeding spotted seabass twice daily to apparent satiation is acceptable and sufficient to achieve good growth and FE, as fish performance was not significantly enhanced when feeding was increased from two to three times daily.  相似文献   

11.
A 56‐day growth trial was conducted to study the utilization of hydrolysed potato starch by juvenile Atlantic salmon Salmo salar L. using a restricted feeding regime. Two diets supplemented with either 15% or 30% hydrolysed potato starch and a control diet without carbohydrate supplementation were each fed to triplicate groups of salmon. Feeding rate varied from 1.4% to 2.0% of body weight per day, so that fish were fed similar amounts of protein and lipid. In spite of the restricted feeding used, no growth stimulation was measured as a consequence of the additional starch intake. No variation was found in protein utilization, measured as protein efficiency ratio values (PER), while feed utilization showed decreased values as starch intake increased. Plasma glucose concentrations did not vary as a consequence of increased starch intake when measured 24 h after feeding, indicating efficient regulation of plasma glucose. In fish fed the 30% starch, the plasma triacylglycerol concentration was significantly increased, which may point to de novo lipid synthesis from the high starch intake. No variation was found in plasma cholesterol or protein concentrations, or asparagine aminotransferase, alanine aminotransferase and lactate dehydrogenase activities. This shows that the fish health status and liver function were normal (no mortality was registered). Liver and muscle showed increased glycogen levels as a function of increased starch intake. The same diets were also fed to juvenile white sturgeon Acipencer transmontanus and hybrid tilapia Oreochromis niloticus×O. aureus. These results are presented separately.  相似文献   

12.
The effect of dietary water content and feeding rate on the growth and food conversion efficiency of turbot was investigated using diets which contained identical amounts of dry nutrient material but different quantities of water, ranging from 0 to 74%. The dietary water content did not significantly influence the growth, composition, condition factor or food conversion efficiency of the turbot. It appeared that, as long as the basic nutrients were formulated so as to produce an adequate diet, the water content was immaterial. The over-riding factor governing growth was the rate of food intake. Comparisons at feeding rates which in energy equivalents ranged from 24 to 72 calories per gram of fish a day, showed that the higher the energy intake the more rapid the growth. At the highest feeding rate, fast growth was accompanied by a marked increase in the condition factor and an elevated lipid content of the fish. The percentage protein content, however, was relatively stable in relation to the feeding rate. Food conversion efficiency was also relatively stable. On average, 40.3% of the dietary protein and 36.3% of the ingested energy was converted into turbot.  相似文献   

13.
An hypothesis on the control of voluntary food intake (appetite) in fish is presented. According to the hypothesis, only two parameters are necessary to design a feeding regime which might result in maximum growth of fish in an aquaculture system. The necessary parameters are maximum voluntary food intake in one meal, and evacuation rate of the stomach. This hypothesis is discussed in relation to empirical data.  相似文献   

14.
在水温12.1～13.9°C下和直径80 cm、高60 cm,水深40 cm的圆形选育缸中研究了不同光照强度(1200lx、600 lx和300 lx)对平均体质量为10.10±0.8g的山女鳟(Oncorhynchus masou masou)幼鱼生长和存活的影响。结果表明,光照强度显著影响山女鳟幼鱼特定生长率(SGR)、肥满度(CF)和变异系数(CV)(P<0.01),高光照强度组SGR和CF值显著高于两个低光照强度组,而CV值则是高光照强度组显著低于两个低光照强度组;高光照强度组摄食率(FI)明显高于两个低光照强度组。实验表明,适度增强光照强度有利于山女鳟幼鱼的生长,这对于优化山女鳟幼鱼培育条件具有指导意义。  相似文献   

15.
Mandarin fish is a typical carnivorous fish, it can accept artificial diet after domestication, which is significantly essential to optimize its artificial diet. Nevertheless, only few studies were conducted on artificial diet of mandarin fish. Therefore, an 8‐week feeding trial was conducted to evaluate the influence of feeding stimulants on growth performance, feed intake and appetite regulation of mandarin fish. In this trial, six diets were formulated, a basal diet contained 80% of Fish Meal without feeding stimulants, named as Control, 0.4% inosinic acid meal, 0.4% L‐Alanine meal, 3% Yeast meal, 3% a commercial squid extract meal and 0.4% betaine meal were added into the basal diet to make five experimental diets, which were named as IM, AM, YM, SVO and BM respectively. At the end of feeding trial, SVO group showed higher feed intake, up‐regulated mRNA expression of neuropeptide Y (NPY) and down‐regulated mRNA expression of pro‐opiomelanocorticoid (POMC) significantly as compared to control group, which suggested that squid extract improved feed acceptability and promoted appetite in mandarin fish. Similarly, compared to control group, SVO group showed low food conversion ratio, high weight gain and SGR, indicated that squid extract enhanced the growth performance. Our results suggested that the appropriate level of squid extract addition could contribute to optimize artificial diet in mandarin fish.  相似文献   

16.
Two trials with Atlantic salmon (Salmo salar) were conducted to evaluate the potential of krill meal to improve feed intake. In the first experiment, after transfer to sea water, salmon smolts were fed diets added 75 or 150 g kg?1 Antarctic krill meal in substitution for fish meal for 13 weeks. The apparent digestibility coefficient for crude protein and the majority of the amino acids was significantly lower in the feeds added krill meal (around 83.5%) than in the control diet (84.9%), whereas the digestibility of crude lipids, dry matter and energy was not significantly different among the three diets. Krill meal addition resulted in higher feed intake, which led to higher growth rates and final body weights. In the second experiment, large salmon were fed a diet containing 100 g kg?1 krill meal for 6 weeks before slaughter. Their feed intake and growth performance were assessed, and fillet and visceral fat contents were measured. Salmon fed the 100 g kg?1 krill meal diet tended to eat more, resulting in significantly increased growth rates, when compared to control fish. Fish fed krill meal also had a significantly lower condition factor.  相似文献   

17.
Physiological studies of growth in animals predict that growth rates should decrease with increasing size, but when Arctic charr, Salvelinus alpinus, were reared together in large groups there was often a positive correlation between initial body size and the growth rate of an individual fish. This suggested that social interactions were important determinants of growth rates and, in the absence of the establishment of direct linear hierarchies, it is suggested that growth suppression is the result of short-term bouts of aggression associated with feeding periods leading to reduced food intake by certain fish. Evidence is presented to show that growth suppression can be reduced by increasing the frequency of feeding.  相似文献   

18.
Feed-restricted fish gain less body mass and storage reserves than well-fed fish, and reduced rates of gain often trigger compensatory responses, characterized by increased appetite (hyperphagia) and growth rate. The results of previous investigations have introduced a hypothesis in which adipose tissue (fat stores) had a regulatory role in governing appetite. An extension of this suggests that hyperphagia may relate to the severity of the feed restriction, and that the compensatory responses will cease once fat reserves are restored relative to body size. This was tested in two trials in which feed-restricted or -deprived postsmolt Atlantic salmon, Salmo salar , became hyperphagic after transfer to excess feeding. At the end of the first trial, previously feed-restricted fish had fully compensated for their lost weight gain compared to continuously fed control fish, but had a leaner body composition (i.e. reduced energy stores) and were still showing signs of compensatory growth. In the second trial, feed deprivation drained body lipids and caused a stronger hyperphagic response than restrictive feeding, although it took longer to develop. Feed intake became coincident when fish had a similar body composition for size, but this occurred at different times. Hence, the fish that had been deprived of feed were smaller than the restricted fish at the end of the trial. The results of the present study demonstrate a link between the magnitude of lipid stores, feed intake and weight gain, and provide some evidence for lipostatic appetite regulation in fish.  相似文献   

19.
To determine seasonal variation in growth and feed conversion ratio (FCR), Atlantic salmon postsmolts (Salmo salar L.) were exposed to either simulated natural photoperiod (SNP) for 12 months or continuous light (LL) from January to June followed by SNP until December. Feed was given to excess and uneaten feed pellets were collected after every meal for estimation of feed intake and calculation of FCR. Body weight increased from 1086 ± 9 g (mean ± SEM) in January to 4970 ± 7 g (SNP) and 5190 ± 23 g (LL) in December. Specific growth rate (SGR), condition factor and feed intake displayed strong seasonal variation in both groups. Measurements of the thermal growth coefficient correlated highly with SGR (r = 0.98, P < 0.05), indicating that the seasonal variation in SGR was independent of temperature and fish size. Continuous light treatment resulted in increased growth from spring, while the fish exposed to simulated natural light had increased growth rate in late summer. Furthermore, LL improved FCR. Periods of high SGR were concurrent with periods of low FCR in both groups.  相似文献   

20.
将270尾均质量约500 g的大西洋鲑随机分为5组,每组2个重复,分别以3次/d、2次/d、1次/d、1次/2 d、1次/3 d的投喂频率饱食投喂56 d,以研究投喂频率对大西洋鲑生长性能、消化率、激素水平和抗氧化指标的影响。试验结果表明,随着投喂频率的降低,大西洋鲑质量增加率和摄食量明显降低,1次/2 d试验组和1次/3 d试验组质量增加率较3次/d试验组分别显著降低50%和75%,摄食量显著降低53%和72%。饵料系数、死亡率、皮质醇和抗氧化指标呈先降后升的趋势;饵料系数和皮质醇2次/d试验组最低,1次/3 d试验组最高,较其他组分别高1.2～2.1倍和0.38～4.78倍。血浆生长激素和甲状腺激素与之呈相反趋势,2次/d试验组各项指标较好;各试验组消化率均呈升高—降低—升高的变化趋势,2次/d和1次/3 d试验组值较高。试验结果表明,500～900 g大西洋鲑的最佳投喂频率为2次/d,在此基础上提高或降低投喂频率均会对大西洋鲑造成应激,对生长和饲料利用率产生负面影响。  相似文献   

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