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Fat Reserves (fat + reserve)
Selected AbstractsComparison of mesenteric and tissue fat content in relation to sexual cycle of the sardine, Sardina pilchardus (Walb., 1792), in the eastern Middle Adriatic fishery grounds (Croatia)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2009B. Musta Summary The study objective was to analyse Sardina pilchardus (Walb., 1792) for mesenteric fat, which is easier to evaluate than the muscle lipid, for comparisons thereof with the sexual cycle and condition of the examined specimens. Fat reserves, moisture and the sexual cycle of sardines were studied from monthly random samples of purse seine catches from March 2004 to February 2005. A total of 1209 specimens were collected (668 males; 541 females). Total length and mass ranged from 13.0 to 19.0 cm and from 16.7 to 51.5 g, respectively. Lipid analyses in muscle tissues were done using the Soxhlet method. An inverse relation between fat content and the sexual cycle was established. Greatest fat quantities were observed in August (72%) during the gonadal resting phase; lowest values were noted in winter, and in spring during the spawning period peak. Moisture content and sexual cycle were positively correlated (r = 0.7913). Total lipids in sardine tissues were higher in females than in males; however, the moisture content was higher in males than in females. [source] Fuel reserves affect migratory orientation of thrushes and sparrows both before and after crossing an ecological barrier near their breeding groundsJOURNAL OF AVIAN BIOLOGY, Issue 1 2009Mark E. Deutschlander Fat reserves influence the orientation of migrating songbirds at ecological barriers, such as expansive water crossings. Upon encountering a body of water, fat migrants usually cross the barrier exhibiting ,forward' migration in a seasonally appropriate direction. In contrast, lean birds often exhibit temporary ,reverse' orientation away from the water, possibly to lead them to suitable habitats for refueling. Most examples of reverse orientation are restricted to autumn migration and, in North America, are largely limited to transcontinental migrants prior to crossing the Gulf of Mexico. Little is known about the orientation of lean birds after crossing an ecological barrier or on the way to their breeding grounds. We examined the effect of fat stores on migratory orientation of both long- and short-distance migrants before and after a water crossing near their breeding grounds; Catharus thrushes (Swainson's and gray-cheeked thrushes, C. ustulatus and C. minimus) and white-throated sparrows Zonotrichiaalbicollis were tested for orientation at the south shore of Lake Ontario during spring and autumn. During both spring and autumn, fat birds oriented in a seasonally appropriate, forward direction. Lean thrushes showed a tendency for reverse orientation upon encountering water in the spring and axial, shoreline orientation after crossing water in the autumn. Lean sparrows were not consistently oriented in any direction during either season. The responses of lean birds may be attributable to their stopover ecology and seasonally-dependent habitat quality. [source] Effect of experimentally altered food abundance on fat reserves of wintering birdsJOURNAL OF ANIMAL ECOLOGY, Issue 5 2003Christopher M. Rogers Summary 1Current models of adaptive fat regulation make opposing predictions concerning the effect of increased winter food supply on size of the avian winter fat reserve. To distinguish between models, food supply was varied experimentally in nature and two measures of size of the fat reserve were taken at food-supplemented sites and non-supplemented sites. 2In two winters, most of the seven species sampled showed slightly higher visible subcutaneous fat class at supplemented than at non-supplemented sites; treatment and species factors were statistically significant. Body mass corrected for wing length showed a similar if non-significant trend. 3A parallel dispersal study of birds colour-banded at non-supplemented sites showed that these birds did not move 0·8 or 1·5 km to use supplemental food at private feeding stations in the study areas. In addition, accipiter hawk attack rate did not differ between supplemented and non-supplemented sites. 4These results are consistent with a model of adaptive fat regulation (based on between-day environmental variability caused by severe weather events) that predicts an increase in the winter fat reserve at increased food supply. Other published studies, all from the north temperate zone, showed the same pattern. 5The present results are inconsistent with a second model (based on within-day foraging interruption) which predicts a decrease in the fat reserve under increased food supply. However, a set of published studies, all from tropical regions or regions with mild maritime climate, showed the decrease at higher food predicted by the second but not the first model. 6Models of adaptive fat regulation in small birds are therefore limited in their predictive power, perhaps because they are developed for environments that differ in the time scale of environmental stochasticity. New studies are needed that explore further the complexities of environment-specific adaptive fat models, e.g. a winter feeding experiment in a tropical bird species. [source] How a mega-grazer copes with the dry season: food and nutrient intake rates by white rhinoceros in the wildFUNCTIONAL ECOLOGY, Issue 2 2006A. M. SHRADER Summary 1Few studies have investigated how free-ranging wild herbivores adjust their food intake rate and nutrient gains during the dry season. Our study focused on the largest extant grazer, the white rhinoceros (Ceratotherium simum Burchell 1817). Field measurements were made on changes in bite mass, bite rate and nutrient concentrations of food eaten during the dry season. 2As the dry season progressed, the quality and availability of food resources declined. During this time white rhinos foraged mainly in high-quality short and woodland grasslands. Late in the dry season they also used flushes of green grass in previously burnt Themeda grasslands. 3Bite mass increased linearly with increasing sward height, while bite rate declined. Intake rate was determined primarily by bite mass and thus tended to increase linearly with sward height. Maximum bite mass and intake rate was obtained in swards >20 cm. 4White rhinos did not compensate for seasonal declines in food quality by adjusting their food intake rate or diet breadth. We suggest that white rhinos mobilize fat reserves to help meet their nutritional needs during the dry season. [source] Measuring natural abundance of 13C in respired CO2: variability and implications for non-invasive dietary analysisFUNCTIONAL ECOLOGY, Issue 6 2001S. E. PERKINS Summary 1,Three experiments were performed, using laboratory mice (Mus musculus) as a model species, to evaluate the potential of using measurements of carbon isotope ratios in expired CO2 for tracing diets. 2,Breath 13C signatures of mice fed a constant diet (,21·4, ± 0·35) reflected their diet, but were depleted by on average ,5·7,. Body mass, sex and age were independent and significant factors correlated with the variability of 13C enrichment in respired CO2. 3,Breath 13C signatures from starved mice (7 h) were lower than unstarved mice by 2·0,. Subsequently when starved mice were fed a small meal of a new diet, breath 13C signatures approached those of the new diets within 15 min, returning to preingestion levels after 105 min. 4,After a permanent diet switch 13C values of breath were not asymptotic within 6 days, possibly because of use of fat reserves during the daytime carrying an isotopic memory of the previous diet. Hence, individual breath 13C signatures may vary according to nutritive state and previous dietary history. 5,Interindividual variability was measured at 3·3,. The implications are that large samples of individuals will be required to distinguish between diets of different populations where the isotopic difference between their diets was small , for example, that expected between herbivorous and carnivorous diets. However, breath would be suitable for distinguishing between dietary intakes of individuals for food types that are isotopically more distinct , such as between C3 and C4 plants. [source] Interactions between land use, habitat use, and population increase in greater snow geese: what are the consequences for natural wetlands?GLOBAL CHANGE BIOLOGY, Issue 6 2005Gilles Gauthier Abstract The North American greater snow goose population has increased dramatically during the last 40 years. We evaluated whether refuge creation, changes in land use on the wintering and staging grounds, and climate warming have contributed to this expansion by affecting the distribution, habitat use, body condition, and migration phenology of birds. We also reviewed the effects of the increasing population on marshes on the wintering grounds, along the migratory routes and on the tundra in summer. Refuges established before 1970 may have contributed to the initial demographic increase. The most important change, however, was the switch from a diet entirely based on marsh plants in spring and winter (rhizomes of Scirpus/Spartina) to one dominated by crops (corn/young grass shoots) during the 1970s and 1980s. Geese now winter further north along the US Atlantic coast, leading to reduced hunting mortality. Their migratory routes now include portions of southwestern Québec where corn production has increased exponentially. Since the mid-1960s, average temperatures have increased by 1,2.4°C throughout the geographic range of geese, which may have contributed to the northward shift in wintering range and an earlier migration in spring. Access to spilled corn in spring improved fat reserves upon departure for the Arctic and may have contributed to a high fecundity. The population increase has led to intense grazing of natural wetlands used by geese although these habitats are still largely undamaged. The foraging in fields allowed the population to exceed limits imposed by natural marshes in winter and spring, but also prevented permanent damage because of their overgrazing. [source] The effect of dominance rank on fat deposition and food hoarding in the Willow Tit Parus montanus, an experimental testIBIS, Issue 1 2003Ken Lundborg We studied the effects of dominance rank on fat deposition and hoarding behaviour in Willow Tits Parus montanus. Dominant individuals can displace subordinates which gives them priority to new food sources; they can also pilfer stored food from subordinates. This gives subordinates less certain access than dominants both to their own caches and to new food sources. Theory predicts that subordinates should invest more than dominants both in body fat reserves and stored food. Empirical evidence is equivocal; some studies have shown that subordinates built up larger reserves than dominants, whereas others show the opposite. In an earlier indoor experiment, Pravosudov and Lucas found no effect of rank on either hoarding rate or fat reserves, but the experimental design was such that the results were ambiguous. This paper reports on a similar, but improved, experiment in outdoor aviaries. However, our results agree with the earlier experiment, since we found no effect of rank on either food storing or fat deposition. The reasons for this are explored. [source] Sex, diet and feeding method-related differences in body condition in the Oystercatcher Haematopus ostralegusIBIS, Issue 1 2001SARAH E.A. Measurements were made of Oystercatcher corpses to find the most reliable measure of body condition in live birds. Total body weight was as accurate as muscle thickness in assessing the weight of the pectoral muscles, a major store of protein reserves. Total body weight was also a good indicator of fat reserves. Wing-length was the most reliable measure of body size. Body condition in live birds was measured as an individual's residual weight derived from a general linear model of (loge) body weight against age, month, (loge) wing-length and time since capture. On the Exe estuary in autumn, there was no significant difference in body condition between same-age Oystercatchers of different diets and feeding methods. In the winter months, however, body condition differed significantly between mussel feeders using different feeding methods, and between mussel feeders and birds that fed on worms and clams. Differences between diet/feeding methods were not the same for each age group. Birds with the highest mean body condition index in adults were mussel hammerers, in immatures mussel stabbers and in juveniles, worm/clam feeders. No significant difference in body condition was found between the sexes in any age group in autumn. In winter, when birds with the same diet/feeding method were considered, females were significantly heavier than males. However, when birds of all diets and feeding methods were combined, weight differences between the sexes were not apparent. We examine reasons why birds with certain diets and feeding methods may be heavier than others in winter, and why females are sometimes heavier than males. We conclude that, in most cases, it is due to differences between birds in their ability to achieve a common target weight. However, we conclude that adult females try to achieve a higher target weight than males, probably as a premigratory and prebreeding strategy. In the light of this, we consider the consequences for adult females, in terms of reproductive success and survival, of specializing in diets and feeding methods associated with lower body weights in winter. [source] Fly or die: the role of fat stores in the growth and development of Grey-headed Albatross Diomedea chrysostoma chicksIBIS, Issue 2 2000KEITH REID Chicks of albatrosses, like other Procellariiformes, become independent at a mass similar to their parents but during growth attain a peak mass some 30% or more greater, before losing mass prior to fledging. The current views are that this high peak mass represents chicks storing fat reserves as an energy sink, or as an insurance against periodic food scarcity, or as a Consequence of natural stochastic variation in provisioning rate. We analysed growth and body composition of Grey-headed Albatross Diomedea chrysostoma chicks at Bird Island, South Georgia in 1984 and 1986, two years of very different food availability. In 1984 when overall breeding success was only 28% (the lowest in 20 years and less than halt that in 1986), chicks were significantly smaller in terms of peak mass (by 37%), primary length (by 25%), liver, lung, heart and kidney size (by 18,34%) and fat (by 75,80%) but not significantly different in terms of skeletal (tarsus, culmen, ulna, sternum) or muscle (pectoral, leg) size. Despite these differences, there were some important similarities in the patterns of growth in both years. Up to the attainment of peak mass, most of the growth of organs and of skeletal structures was completed and little fat was deposited. In the remaining part of the chick-rearing period, feather growth and acquisition of fat stores were undertaken. Thus Grey-headed Albatross chicks begin to acquire substantial fat stores only during the later part of the development period; this is contrary to the predictions of any of the existing hypotheses concerning provisioning patterns and the role of fat stores in Procellariiformes. We propose that the deposition of fat in the later stages of chick growth is an adaptation to: (a) ensure against energy demands and/or nutritional stress affecting the quality of flight feathers (many of which are not renewed for up to three years after fledging); and (b) provide an energy reserve for chicks to use in the critical period immediately after independence. [source] Effect of experimentally altered food abundance on fat reserves of wintering birdsJOURNAL OF ANIMAL ECOLOGY, Issue 5 2003Christopher M. Rogers Summary 1Current models of adaptive fat regulation make opposing predictions concerning the effect of increased winter food supply on size of the avian winter fat reserve. To distinguish between models, food supply was varied experimentally in nature and two measures of size of the fat reserve were taken at food-supplemented sites and non-supplemented sites. 2In two winters, most of the seven species sampled showed slightly higher visible subcutaneous fat class at supplemented than at non-supplemented sites; treatment and species factors were statistically significant. Body mass corrected for wing length showed a similar if non-significant trend. 3A parallel dispersal study of birds colour-banded at non-supplemented sites showed that these birds did not move 0·8 or 1·5 km to use supplemental food at private feeding stations in the study areas. In addition, accipiter hawk attack rate did not differ between supplemented and non-supplemented sites. 4These results are consistent with a model of adaptive fat regulation (based on between-day environmental variability caused by severe weather events) that predicts an increase in the winter fat reserve at increased food supply. Other published studies, all from the north temperate zone, showed the same pattern. 5The present results are inconsistent with a second model (based on within-day foraging interruption) which predicts a decrease in the fat reserve under increased food supply. However, a set of published studies, all from tropical regions or regions with mild maritime climate, showed the decrease at higher food predicted by the second but not the first model. 6Models of adaptive fat regulation in small birds are therefore limited in their predictive power, perhaps because they are developed for environments that differ in the time scale of environmental stochasticity. New studies are needed that explore further the complexities of environment-specific adaptive fat models, e.g. a winter feeding experiment in a tropical bird species. [source] Population dynamics of the pipistrelle bat: effects of sex, age and winter weather on seasonal survivalJOURNAL OF ANIMAL ECOLOGY, Issue 2 2003Thomas Sendor Summary 1Life-history theory assumes increased mortality at certain stages such as hibernation. However, seasonal variation of survival rates of hibernating mammals has rarely been estimated. In this study, apparent survival of pipistrelle bats (Pipistrellus pipistrellus) hibernating and performing summer swarming at a large hibernaculum (Marburg Castle, Hesse, Germany), was modelled using seasonal (summer/winter) capture,recapture data for the years 1996,2000. The spring survival interval includes the period of arousal at the end of hibernation and therefore validly measures survival associated with hibernation. 2In five summers and four winters, 15 839 bats were captured and released (13 082 individuals) and 3403 recaptures recorded. Analysis was complicated by transience and trap-dependence. Recapture rates varied seasonally and by group. The autumnal survival estimates were negatively biased due to transience effects that could not be taken into account. 3Survival could be modelled using two age-classes, with reduced first-year juvenile survival. The age effect persisted over the first autumn and spring. There was virtually no evidence for sex-specific survival rates; male and female survival were found to be almost equal. In the best-fitting models, survival rates varied over time and differed among sexes and age-classes by a constant amount. Between years, there was only a small variation in spring survival, which could not be explained by winter severity. 4Adult spring survival was surprisingly high, averaging 0·892 (= 0·028). No evidence for increased mortality during hibernation could be found. This contradicted the expectation of reduced over-winter survival due to depleted fat reserves at the end of hibernation. Thus, hibernation does apparently not entail a survival cost for the pipistrelle bat. Rough estimates of annual adult survival averaged 0·799 ( = 0·051), which considerably exceeds previous estimates; annual juvenile survival was estimated at 0·527 ( = 0·095). Hence, previous studies have substantially underestimated pipistrelle bat survival. Possible consequences of these findings for various aspects of life histories are discussed. [source] Effects of fat reserves on annual apparent survival of blackbirds Turdus merulaJOURNAL OF ANIMAL ECOLOGY, Issue 1 2003Mark W. Miller Summary 1Fat reserves are stored energy that may help birds survive periods of harsh winter weather. This hypothesis predicts that annual apparent survival is higher for birds with large fat reserves than for birds with few or no fat reserves in winter. 2Blackbirds (Turdus merula Linnaeus) were ringed in central Italy from 16 November to 20 February during 1990,2001. Fat scores were recorded for each bird. We used these capture,mark,recapture data for 1703 blackbirds to estimate the effect of large fat reserves on annual apparent survival, while controlling for transients, using computer programs surviv and mark. Probability of birds retaining large fat reserves, or retaining few fat reserves, over 2 successive years was also estimated. 3Birds with large fat reserves did not have higher estimated annual apparent survival than birds with few fat reserves (,,large= ,,few= 0·595, SE = 0·043), inconsistent with our prediction. No effects of age, sex or year were detected on annual apparent survival. Birds with few fat reserves in any given year tended to have few fat reserves the following year (, SE = 0·052). Birds with large fat reserves in any given year were unlikely to have large fat reserves the next year (, SE = 0·080). 4Large fat reserves may not increase annual survival of blackbirds wintering in central Italy. Winter weather in our study area may be too mild to effect survival. Alternatively, increased predation risk associated with large fat reserves may counteract any benefits of reduced starvation risk. [source] Reproduction in puyen, Galaxias maculatus (Pisces: Galaxiidae), in the southernmost extreme of distributionJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2007C. C. Boy Summary Reproductive aspects of a peripheral population of Galaxias maculatus are described and the relationship with the physiology and handling of energetic reserves under marginal environmental conditions is investigated. The G. maculatus population of Tierra del Fuego has an extended reproductive season, with differences in timing and duration compared to other populations of continental Patagonia, New Zealand and Australia. Elevated gonadosomatic indexes (IG) were observed during this period in both sexes (maximum IG = 33.49% males; 35.94% females). The high abundance of mature males (with high IG values) on the spawning grounds during the reproductive season suggests that they were waiting for the return of the mature females. Larger females reached total maturation at the beginning of the reproductive season, whereas the size of maturing females diminished toward the end (mean TL = 96 mm, October; 70 mm, February). Both sexes showed an extremely high investment in reproduction, reaching a maximum IG of about 35% for both sexes. At the beginning of the reproductive season females reached the maximum median IH (3.37%) and males the minimum (0.96%), suggesting differences in the role of the liver in the management of energetic reserves during sexual maturation. The variation in the fat index (IF) suggests that fat reserves were used to survive winter (maximum median IF > 1%, autumn; minimum about 0.2%, spring). [source] Characterizing the nutritional strategy of incubating king eiders Somateria spectabilis in northern AlaskaJOURNAL OF AVIAN BIOLOGY, Issue 6 2008Rebecca L. Bentzen We measured plasma concentrations of variables associated with lipid metabolism (free fatty acids, glycerol, triglyceride, and ,-hydroxybutyrate), protein metabolism (uric acid), and baseline corticosterone to characterize the nutritional state of incubating king eiders Somateria spectabilis and relate this to incubation constancy at two sites, Kuparuk and Teshekpuk, in northern Alaska. King eiders at both sites appeared to employ a partial-income incubation strategy, relying on both endogenous and exogenous energy resources. Females maintained high invariant levels of free fatty acids, ,-hydroxybutyrate, and glycerol throughout incubation, indicating that fat reserves were a major energy source, and not completely depleted during incubation. Similarly, uric acid did not increase, suggesting effective protein sparing or protein ingestion and adequate lipid reserves throughout incubation. Baseline corticosterone and triglyceride levels increased during incubation, indicative of an increase in foraging during late stages of incubation. Incubating females at Kuparuk had higher triglyceride concentrations but also had higher ,-hydroxybutyrate concentrations than females at Teshekpuk. This dichotomy may reflect a short-term signal of feeding overlaying the longer-term signal of reliance on endogenous lipid reserves due to higher food intake yet higher metabolic costs at Kuparuk because of its colder environment. Incubation constancy was not correlated with plasma concentrations of lipid or protein metabolites. [source] Thyrotrophin-Releasing Hormone Decreases Feeding and Increases Body Temperature, Activity and Oxygen Consumption in Siberian HamstersJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2007S. Schuhler Thyrotrophin-releasing hormone (TRH) is known to play an important role in the control of food intake and energy metabolism in addition to its actions on the pituitary-thyroid axis. We have previously shown that central administration of TRH decreases food intake in Siberian hamsters. This species is being increasingly used as a physiological rodent model in which to understand hypothalamic control of long-term changes in energy balance because it accumulates fat reserves in long summer photoperiods, and decreases food intake and body weight when exposed to short winter photoperiods. The objectives of our study in Siberian hamsters were: (i) to investigate whether peripheral administration of TRH would mimic the effects of central administration of TRH on food intake and whether these effects would differ dependent upon the ambient photoperiod; (ii) to determine whether TRH would have an effect on energy expenditure; and (iii) to investigate the potential sites of action of TRH. Both peripheral (5,50 mg/kg body weight; i.p.) and central (0.5 µg/ml; i.c.v.) administration of TRH decreased food intake, and increased locomotor activity, body temperature and oxygen consumption in the Siberian hamster, with a rapid onset and short duration of action. Systemic treatment with TRH was equally effective in suppressing feeding regardless of ambient photoperiod. The acute effects of TRH are likely to be centrally mediated and independent of its role in the control of the production of thyroid hormones. We conclude that TRH functions to promote a catabolic energetic state by co-ordinating acute central and chronic peripheral (thyroid-mediated) function. [source] Lipid dynamics in the viperine snake, Natrix maura, from the Ebro Delta (NE Spain)OIKOS, Issue 1 2004Xavier Santos Body reserves play a major role in several aspects of vertebrate biology. Accurate identification and quantification of body reserves constitute a useful contribution to the better understanding of the energetic costs of reproduction and the implication of food availability in life history traits of organisms. In this study, lipid content in fat bodies, liver and muscle of the viperine snake (Natrix maura) were measured along an active season. Samples were collected monthly from a natural population of the Ebro Delta Natural Park (NE Spain). This methodology pointed out that lipids stored in fat bodies were the main energetic source during reproduction. In addition, lipids stored in liver appeared to be critical for vitellogenesis, while lipids stored in muscle turned out to be a supplementary energetic resource to fuel reproductive effort. Relationships between changes in body reserves and prey availability in canals of the Ebro Delta were also considered. In males, lipid reserves presented a positive correlation with food availability. On the contrary, lipid reserves in female viperine snakes decreased during vitellogenesis even though food availability increased in this period, which suggests a quick transfer of body lipids to clutch. In April, when rice fields of the Ebro Delta were dry and aquatic prey was scarce for viperine snakes, males and females presented a lower lipid content in fat bodies, liver and muscle than they did in other months, showing a clear link between prey availability and body reserves during food shortage. Thus, patterns of variation in fat levels indicated that Natrix maura is a capital breeder since it acquires resources in advance and stores them until they are invested during the reproductive period. Nevertheless, the shortage in April forces Natrix maura to turn into a facultative income breeder to fuel vitellogenesis. Finally, fat reserves in body components were compared with an estimate of body condition calculated by the residuals from the regression of body mass on body length. In male viperine snakes, the estimate of body condition was correlated with fat levels, revealing that this index is useful to measure condition in living individuals. On the contrary, body condition in females was not correlated with fat levels, which suggests that it is not appropriate to infer condition in female viperine snakes since it depends on the reproductive status of the individuals. [source] Impact of seasonal scarcity on energy balance and body composition in peasant adolescents from Calakmul, Campeche MexicoAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2007José A. Alayón Gamboa A time allocation and anthropometric study were performed on 46 male and 38 female adolescents from 16 peasant households from two different adaptive strategies in the municipio of Calakmul, Campeche Mexico to see if they could maintain energy balance during the annual scarcity season. These strategies were called: "household subsistence agricultural strategy" (HSA) and "household commercial agricultural strategy" (HCA). Each month, from June 2001 to May 2002, adolescents were measured and followed for 24 h. Their activities were recorded at 15 min intervals. Weight for age (W/A), height for age (H/A), body mass index (BMI), arm muscle area, arm fat area, total energy expenditure (TEE), activity energy expenditure (AEE), and basal metabolic rate (BMR) were estimated and the data compared between seasons using a repeated measurements analysis of variance. The results suggest that HCA offers their adolescents better buffering against seasonal scarcity, and that HSA males are better protected than females. HCA adolescents didn't show significant losses of weight, and HCA females lost body fat during the scarcity season. HSA vulnerability was observed in W/A and BMI z score reductions during the scarcity season. It also reflected itself in stunted adolescent males and adolescent females with fewer fat reserves. HSA adolescents reduced their BMR to down regulate their energy expenditure during the scarcity season without reducing TEE and physical activity levels. HSA females lost muscle mass during the scarcity season while HSA males didn't. This difference was associated with a more demanding work schedule throughout the year for females. Am. J. Hum. Biol., 2007. © 2007 Wiley-Liss, Inc. [source] Weight gain and lipid deposition in Atlantic salmon, Salmo salar, during compensatory growth: evidence for lipostatic regulation?AQUACULTURE RESEARCH, Issue 12 2001S J S Johansen Abstract 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. [source] | |||||||||||||||||||||||||