Body Energy Gain Research Articles

Chronic REM sleep restriction in young rats increases energy expenditure with no change in food intake.

What is the central question of this study? What are the effects of different periods of REM sleep restriction (7, 14 and 21days) on metabolic parameters in young rats? What is the main finding and its importance? Animals submitted to each period of REM sleep deprivation showed a negative energy balance, with reduced body weight gain, body energy gain and gross food efficiency, less body fat content, and increased energy expenditure. There was no increase in food intake after any of the REM sleep restriction periods. In young rats, negative energy balance is not compensated by increased dietary intake as observed in adult rats. Reduced sleep is associated with metabolic alterations, not only in adults, but also in children and adolescents. Several studies have shown that sleep restricted (SR) adult rats exhibit metabolic changes, followed by increased food intake, but few have evaluated these functions in young animals. The aim of the present study was to establish the metabolic parameters of young rats subjected to different periods of REM sleep restriction and to propose a correction factor for the correct measurement of food intake. Young male Wistar rats were distributed in control and SR groups for 7, 14 or 21days. Sleep restriction was performed by the single platform method for 18 h. Regardless of the length of sleep restriction, all SR rats had a negative energy balance, evidenced by reduction in body weight gain, body energy gain and gross food efficiency, accompanied by increased energy expenditure. In addition, sleep restriction reduced body fat content throughout the entire period. Discounting food spillage, there was no increase in food intake by SR rats. In conclusion, the present study revealed metabolic changes in SR young rats after different lengths of REM sleep restriction and that weight loss and increased energy expenditure were not compensated by increased dietary intake as occurs in adult rats, indicating that young rats use other mechanisms to cope with the negative energy balance caused by sleep restriction. In addition, we propose a correction factor for food intake, to prevent overestimation of this parameter, due to food spillage in the water containers.

Effects of dietary sodium acetate on food intake, weight gain, intestinal digestive enzyme activities, energy metabolism and gut microbiota in cultured fish: Zebrafish as a model

Acetate is the most abundant short-chain fatty acids (SCFAs) in the gastrointestinal tract of fish. The aim of this study was to investigate the effects of dietary sodium acetate (NaAc) on food intake, weight gain, intestinal digestive enzyme activities, energy metabolism and gut microbiota of zebrafish (Danio rerio). In this study, 1-month-old zebrafish were fed with 0.15% NaAc diet for 4 weeks under satiation feeding. At the end of feeding trial, the level of intestinal acetate in the fish fed with 0.15% NaAc containing diet were significantly increased (p < .05), which was accompanied by a higher weight gain and daily feeding rate compared with the control group (p < .05). Dietary supplementation of 0.15% NaAc significantly promoted the body fat mass, energy gain and energy conversion efficiency, as well as intestinal digestive enzyme (amylase) activity in fish (p < .05). The expression of food intake-related genes (ghre, npy and npy7R) in the brain of fish fed on the diet contacting 0.15% NaAc was higher than that of the control group. Consistently, intracerebroventricular injection of NaAc in the brain of zebrafish also increased the expression of genes related to food intake. The effects of NaAc on orexigenic genes expression in the brain of zebrafish could be prevented by co-injection of atropine, suggesting that acetate played a direct role in controlling appetite through the parasympathetic nerve system. Moreover, there was significantly decrease (p < .05) in the relative abundance of Plesiomonas genus in the fish gut fed on the diet supplemented with NaAc. These data suggest that NaAc has a potential value as fish feed additive in aquaculture.

Relationship between residual feed intake and digestibility for lactating Holstein cows fed high and low starch diets

We determined if differences in digestibility among cows explained variation in residual feed intake (RFI) in 4 crossover design experiments. Lactating Holstein cows (n=109; 120±30d in milk; mean ± SD) were fed diets high (HS) or low (LS) in starch. The HS diets were 30% (±1.8%) starch and 27% (±1.2%) neutral detergent fiber (NDF); LS diets were 14% (±2.2%) starch and 40% (±5.3%) NDF. Each experiment consisted of two 28-d treatment periods, with apparent total-tract digestibility measured using indigestible NDF as an internal marker during the last 5d of each period. Individual cow dry matter (DM) intake and milk yield were recorded daily, body weight was measured 3 to 5 times per week, and milk components were analyzed 2 d/wk. Individual DM intake was regressed on milk energy output, metabolic body weight, body energy gain, and fixed effects of parity, experiment, cohort (a group of cows that received treatments in the same sequence) nested within experiment, and diet nested within cohort and experiment, with the residual being RFI. High RFI cows ate more than expected and were deemed less efficient. Residual feed intake correlated negatively with digestibility of starch for both HS (r=−0.31) and LS (r=−0.23) diets, and with digestibilities of DM (r=−0.30) and NDF (r=−0.23) for LS diets but was not correlated with DM or NDF digestibility for HS diets. For each cohort within an experiment, cows were classified as high RFI (HRFI; >0.5 SD), medium RFI (MRFI; ±0.5 SD), and low RFI (LRFI; <−0.5 SD). Digestibility of DM was similar (~66%) among HRFI and LRFI for HS diets but greater for LRFI when fed LS diets (64 vs. 62%). For LS diets, digestibility of DM could account for up to 31% of the differences among HRFI and LRFI for apparent diet energy density, as determined from individual cow performance, indicating that digestibility explains some of the between-animal differences for the ability to convert gross energy into net energy. Some of the differences in digestibility between HRFI and LRFI were expected because cows with high RFI eat at a greater multiple of maintenance, and greater intake is associated with increased passage rate and digestibility depression. Based on these data, we conclude that a cow’s digestive ability explains none of the variation in RFI for cows eating high starch diets but 9 to 31% of the variation in RFI when cows are fed low starch diets. Perhaps differences in other metabolic processes, such as tissue turnover, heat production, or others related to maintenance, can account for more variation in RFI than digestibility.

Effects of partly replacing dietary starch with fiber and fat on milk production and energy partitioning

The effects of partly replacing dietary starch with fiber and fat to provide a diet with similar net energy for lactation (NEL) density on yields of milk and milk components and on energy partitioning were evaluated in a crossover design experiment. Holstein cows (n=32; 109±22 d in milk, mean ± standard deviation) were randomly assigned to treatment sequence. Treatments were a high-starch diet containing 33% corn grain (mixture of dry ground and high-moisture corn; HS) or a high-fiber, high-fat diet containing 2.5% palmitic acid-enriched fatty acid (FA) supplement (HFF). Diets contained corn silage, alfalfa silage, and wheat straw as forage sources; HS contained 32% starch, 3.2% FA, and 25% neutral detergent fiber, whereas HFF contained 16% starch, 5.4% FA, and 33% neutral detergent fiber. Compared with HS, the HFF treatment reduced milk yield, milk protein concentration, and milk protein yield, but increased milk fat concentration, milk fat yield, milk energy output, and milk to feed ratio (energy-corrected milk/dry matter intake). The HFF treatment reduced the yield of de novo synthesized (<16-carbon) milk FA and increased the yield of 16-carbon milk FA. Yield of preformed (>16-carbon) milk FA was not different. The HFF treatment increased plasma concentrations of triglycerides and nonesterified fatty acids, but decreased plasma concentration of insulin. Compared with HS, the HFF treatment reduced body weight gain, change in body condition score, and fat thickness over the rump and rib. Calculated body energy gain, as a fraction of NEL use, was less for HFF than HS, whereas milk energy as a fraction of NEL use was increased for HFF. We concluded that the 2 treatments resulted in similar apparent NEL densities and intakes, but the HS treatment partitioned more energy toward body gain whereas the HFF treatment partitioned more energy toward milk. A high-fiber, high-fat diet might diminish the incidence of over conditioning in mid-lactation cows while maintaining high milk production.

Residual feed intake is repeatable for lactating Holstein dairy cows fed high and low starch diets

Residual feed intake (RFI) is a tool to quantify feed efficiency in livestock and is commonly used to assess feed efficiency independent of production level, body weight (BW), or BW change. Lactating Holstein cows (n=109; 44 primiparous and 65 multiparous), averaging (mean ± standard deviation, SD) 665±77kg of BW, 42±9kg of milk/d, and 120±30 d postpartum, were fed diets of high (HI) or low (LO) starch content in 4 crossover experiments with two 28-d treatment periods. The LO diets were ~40% neutral detergent fiber (NDF) and ~14% starch and the HI diets were ~26% NDF and ~30% starch. Individual dry matter intake (DMI) of a cow was modeled as a function of milk energy output, metabolic BW, body energy change, and fixed effects of parity, experiment, cohort nested within experiment, and diet nested within cohort and experiment; RFI for each cow was the residual error term. Cows were classified as high (>0.5 SD of the mean), medium (±0.5 SD of the mean), or low (<−0.5 SD of the mean) RFI. On average, for the linear model used to determine RFI for individual cows, each unit increase in milk energy output, metabolic BW, or body energy gain was associated with 0.35, 0.09, or 0.05kg increase in DMI, respectively. When compared with LO diets, HI diets increased energy partitioning to body energy gain and tended to increase DMI. The correlation between RFI when cows were fed HI diets and RFI when cows were fed LO diets was 0.73 and was similar across each parity and experiment. Fifty-six percent of cows maintained the same RFI classification (high, medium, or low RFI) and only 4 of 109 cows changed from high RFI to low RFI or vice versa when diets were changed. Milk:feed, income over feed cost, and DMI were also highly repeatable (r=0.72, 0.84, and 0.92, respectively). We achieved significant changes in milk yield and component concentration as well as energy partitioning between HI and LO diets and still determined RFI to be repeatable across diets. We conclude that RFI is reasonably repeatable for a wide range of dietary starch levels fed to mid-lactation cows, so that cows that have low RFI when fed high corn diets will likely also have low RFI when fed diets high in nonforage fiber sources.

Predictors of body composition and body energy changes in response to chronic overfeeding

ObjectiveWe have previously shown that 24 young lean men (12 pairs of identical twins) subjected to a standardized 353 MJ (84 000 kcal) overfeeding protocol over 100 days exhibited individual differences in body weight and composition gains. The mean (+SD) gains in fat mass (FM) and fat-free mass (FFM) were 5.4+1.9 kg and 2.7+1.5 kg for a total body energy (BE) gain of 221+75 MJ representing 63% of the energy surplus consumed. We report here on the most important baseline correlates of these overfeeding-induced changes with the aim of identifying biomarkers of the response.ResultsBaseline maximal oxygen uptake per kilogram body mass was negatively correlated with gains in weight, FM, and BE (all p<0.05). Enzyme activities indicative of skeletal muscle oxidative potential correlated with gains in FM and BE (all p<0.05). Baseline TSH levels in response to a TRH stimulation correlated positively with changes in FM-to-FFM ratio (p<0.05). Plasma concentrations of androstenediol-sulfate, dehydroepiandrosterone, and 17-hydroxy pregnenolone were negatively correlated with gains in FM and BE (0.01<p<0.05), while level of estrone was negatively and androsterone-glucoronide was positively correlated with FFM gains (p<0.05). Baseline leptin and abdominal fat cell size correlated positively with gains in weight, FM, and BE (p<0.05). When compared to the six highest BE gainers, the six lowest gainers exhibited higher thermic effect of a meal (TEM) and plasma levels of total testosterone, cortisol, estradiol, androstenedione, and androstenediol-sulfate (all p<0.05). High baseline levels of total TEM, testosterone, and androstenediol-sulfate were associated with lower FM gains whereas high baseline levels of FT4 and estrone were found in low-FFM gainers.ConclusionAlthough none of the variables exerted individually an overwhelmingly strong influence on overfeeding-induced changes, baseline FFM, maximal oxygen uptake, muscle oxidative capacity, androgens, and leptin levels were the most consistent significant biomarkers of the responsiveness to chronic overfeeding.

Interspecies differences in the empty body chemical composition of domestic animals

Domestication of animals has resulted in phenotypic changes by means of natural and human-directed selection. Body composition is important for farm animals because it reflects the status of energy reserves. Thus, there is the possibility that farm animals as providers of food have been more affected by human-directed selection for body composition than laboratory animals. In this study, an analysis was conducted to determine what similarities and differences in body composition occur between farm and laboratory animals using literature data obtained from seven comparative slaughter studies (n = 136 observations). Farm animals from four species (cattle, goats, pigs and sheep) were all castrated males, whereas laboratory animals from three species (dogs, mice and rats) comprised males and/or females. All animals were fed ad libitum. The allometric equation, Y = aXb, was used to determine the influence of species on the accretion rates of chemical components (Y, kg) relative to the growth of the empty body, fat-free empty body or protein weights (X, kg). There were differences between farm and laboratory animals in terms of the allometric growth coefficients for chemical components relative to the empty BW and fat-free empty BW (P < 0.01); farm animals had more rapid accretion rates of fat (P < 0.01) but laboratory animals had more rapid accretion rates of protein, water and ash (P < 0.01). In contrast, there was no difference in terms of the allometric growth coefficients for protein and water within farm animals (P > 0.2). The allometric growth coefficients for ash weight relative to protein weight for six species except sheep were not different from a value of 1 (P > 0.1), whereas that of sheep was smaller than 1 (P < 0.01). When compared at the same fat content of the empty body, the rate of change in water content (%) per unit change in fat content (%) was not different (P > 0.05) across farm animal species and similar ash-to-protein ratios were obtained except for dogs. The fraction of empty body energy gain retained as fat increased in a curvilinear manner, and there was little variation among farm animals at the same fat content of the empty body. These findings may provide the opportunity to develop a general model to predict empty body composition across farm animal species. In contrast, there were considerable differences of chemical body composition between farm and laboratory animals.

Effects of winter growing programs on subsequent feedlot performance, carcass characteristics, body composition, and energy requirements of beef steers12

The purpose of this study was to investigate the effects of winter growing program on subsequent finishing performance, carcass merit, and body composition of beef steers. Four steers were slaughtered to determine initial body composition. Remaining steers (n = 256) were blocked by BW and randomly allotted to 1 of 4 treatment groups: 1) ad libitum fed a high-concentrate diet (CF), 2) grazed on wheat pasture (WP), 3) fed a sorghum silage-based diet (SF), or 4) program fed a high-concentrate diet (PF). Steers in the WP, SF, and PF groups were managed to achieve approximately equal rates of BW gain. After the growing phase (112 d), 6 steers were randomly selected from the WP, SF, and PF treatments for determination of body composition. Remaining steers were adapted to a high-concentrate diet for finishing and slaughtered at 1.27 cm of 12th-rib fat. Six steers from each treatment were used to determine carcass, offal, and empty body composition. During the growing phase, WP, SF, and PF steers gained 1.15, 1.10, and 1.18 kg/d, respectively, and ME intake did not differ (P = 0.50) among treatments. Program-fed and SF steers had greater (P < 0.05) offal and empty body fat content than WP steers. Gain in offal and empty body fat was greatest (P < 0.05) for PF steers, intermediate for SF steers, and least for WP steers. During the finishing phase (123, 104, 104, 196 d for WP, SF, PF, and CF, respectively) DMI was greater (P < 0.01) for SF steers (10.9 kg/d) than for PF steers (10.1 kg/d); WP steers were intermediate (10.4 kg/d). Daily BW gain was greatest (P < 0.05) for SF steers (2.02 kg/d), intermediate for PF steers (1.85 kg/d), and least for WP and CF steers (1.64 and 1.63 kg/d, respectively). Accretion (kg/d) of carcass and empty body mass was less (P < 0.05) for WP and CF steers compared with PF and SF steers. Calf-fed steers had greater (P < 0.05) fat content of offal than SF and PF steers; WP steers were intermediate. Gain in empty body and carcass energy (Mcal/d) was greater (P < 0.05) for PF steers than CF steers with SF and WP steers being intermediate. At slaughter, SF steers had reduced (P < 0.01) yield grades and greater marbling scores compared with CF and WP steers; PF steers were intermediate. In conclusion, growing programs that increase fat composition of feeder calves did not negatively affect subsequent finishing performance. Finishing steers as calves may reduce retained energy of carcass tissues and increase internal fat during high-grain feeding compared with steers that previously underwent a growing program.

Prey selection of the black stork in the African wintering area

AbstractTo determine what kind of factors are implied in the decline of long‐distance birds, knowledge on feeding ecology in breeding and wintering areas is essential. We present the first study recording the quantity and quality of food eaten by a population of black storks Ciconia nigra in the Africa wintering zone, as well as prey abundance in the field by testing an eventual foraging strategy based on the selection of biotic parameters of fish prey (body size, energy gain, swimming speed and fish armaments). Black storks preferentially selected two fish species of Siluriforms that were not the most abundant species in the field. Storks carried out interspecific selection according to the swimming speed of fish species and intraspecific selection depending on prey size, probably to avoid defensive armaments of the preferred fish prey. Small fishes consumed by the birds constituted 91% of the diet and 45% of the total food energy intake. Small fishes were more frequently caught than large ones, even if the storks sometimes took the opportunity to catch large fishes that provided a high energy gain. Energy assimilation of black storks is almost twofold higher than the estimated daily energy expenditure. This study suggests that the quantity of food would satisfy the energy requirements of the species during the winter in Africa, enable them to store reserves and ensure their survival in the African areas.

A Theoretical Framework for Deriving Direct Economic Values for Body Tissue Mobilization Traits in Dairy Cattle

The aim of this study was to simplify the description of body tissue mobilization during first lactation into 3 parameters for which breeding values can be estimated. The traits defined were 1) the rate at which a bull's daughters lost body energy early in lactation, 2) the maximum drop in body energy content, and 3) the rate at which a bull's daughters regained body energy after nadir. A theoretical framework was developed to derive economic values for the 3 traits of body tissue mobilization. The UK population parameters were used in the economic framework to derive economic weights for body tissue mobilization during lactation. Assuming the average calving pattern in the UK, the economic value for the maximum drop in body energy content is small and negative at −0.14 pence (p/MJ). The economic value for the rate of loss of body energy in early lactation is also negative (−3.1 p/MJ) and for the rate of body energy gain in later lactation is positive (19.7 p/MJ). Results showed that the economic values for the 3 traits of body tissue mobilization change dramatically depending on the date of calving due to changes in feed costs in different seasons. The framework was developed to accommodate various system parameters (e.g., the costs of differing energy sources throughout the year and calving pattern), thus allowing for farm-system–specific economic values for body tissue mobilization. The framework provides a method to select sires based on an index of body energy mobilization of their daughters.

Influence of dietary non-essential amino acid profile on growth performance and amino acid metabolism of Nile tilapia, Oreochromis niloticus (L.)

The quality of dietary protein is an important factor influencing the growth performance of fish. To evaluate the quality of protein, the variables commonly studied are the composition of the essential amino acids, the digestibility and the protein use efficiency. The goal of the present experiment was to test the effect of the dietary non-essential amino acid composition on the growth of Nile tilapia (Oreochromis niloticus). The fish were fed three purified diets differing only in their non-essential amino acid composition. The influence of the experimental diets on the growth performance, on the activity of enzymes involved in the amino acid metabolism, aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT), and on whole body delta(15)N values was investigated. Body mass, lipid, protein and energy gain differed significantly between the feeding groups. The activity of ASAT in the whole liver was significantly higher in fish with a positive protein balance compared to fish which lost protein. Whole body delta(15)N values of fish were negatively correlated with their body mass gain. Despite the poor utilisation of synthetic amino acids, the experiment indicates the importance of the dietary non-essential amino acid composition for the growth performance of fish. The study reveals the possibility to trace the utilisation of synthetic amino acids by determining the isotopic composition of dietary amino acids and tissues or whole bodies of animals.

Effect of high-fat feeding on metabolic efficiency and mitochondrial oxidative capacity in adult rats.

The changes in metabolic efficiency, body composition, and nutrient partitioning induced by high-fat feeding were evaluated in adult rats (90 d of age). The alterations in serum free triiodothyronine, insulin, and leptin levels, as well as in hepatic and skeletal muscle metabolism, were also assessed. Rats were fed either a low- or a high-fat diet for 2 weeks. Relative to the low-fat feeding, energy intake and expenditure, as well as body-energy gain, lipid gain, and energetic efficiency, were increased by the high-fat feeding. Increased serum leptin levels accompanied these variations. A positive correlation between serum leptin levels and percentage of body fat was found in the rats fed the low- or high-fat diet, with a significant divergence between the slope of the regression lines. Furthermore, a negative correlation between serum leptin level and energy intake was found in the rats fed the low-fat diet, while a positive correlation was found in the rats fed the high-fat diet. Finally, the high-fat feeding decreased the hepatic and skeletal muscle mitochondrial oxidative capacity. It is concluded that, in adult rats, a nutritional factor such as a high level of fat in the diet induces obesity, leptin resistance, and impairment of mitochondrial capacity, all phenomena typical of unrestrained aged rats.

D-psicose is a rare sugar that provides no energy to growing rats.

D-Psicose (D-ribo-2-hexulose), a C-3 epimer of D-fructose, is present in small quantities in commercial carbohydrate complexes and agricultural products. We have previously reported that D-psicose supplements in diets suppressed hepatic lipogenic enzyme activity The lower fat accumulation in rats fed D-psicose may be due to lower lipogenesis in the liver. The present study examined the energy available in D-psicose for rat growth. Male Wistar rats received 7 g daily of a basal diet to which fixed amounts of sucrose, D-fructose, or D-psicose (0.5-2.0 g) were added for 20 d. Body weight gain and body energy gain increased with increases in sucrose and D-fructose, but not with D-psicose. One gram of sucrose, D-fructose, and D-psicose produced a net energy gain of 2.29, 1.76, and 0.007 kcal, respectively. The efficiency of energy deposition from D-psicose was 0.3% that of sucrose. The energy value of D-psicose was effectively zero. These results suggest that D-psicose is a rare sugar providing zero energy that may be useful in sweeteners for obese people as an aid for weight reduction.

Compensatory growth in the gibel carp following feed deprivation: temporal patterns in growth, nutrient deposition, feed intake and body composition

To investigate the nature of compenstory growth in fish, an 8 week study at 28°C was performed on juvenile gibel carp Carassius auratus gibelio weighing 6·6 g. Fish were starved for 0 (control), 1 (S1) or 2 (S2) weeks and then re‐fed to satiation for 5 weeks. Weekly changes in weight gain, feed intake and body composition were monitored during re‐feeding. No significant difference was found in final body weight between the three groups, indicating complete compensation in the deprived fish. The deprived groups caught up in body weight with that of the control after 2 weeks of re‐feeding. Body fat: lean body mass ratio was restored to the control level within 1 week of re‐feeding. In the re‐feeding period, weekly gains in body weight, protein, lipid, ash and energy in the S1 group were significantly higher than in the controls for 1 week. For the S2 group, weekly gains in body weight, lipid, ash and energy were higher than in the controls for 2 weeks, and gain in protein was higher than in the controls for 3 weeks, though gain in body energy became elevated again during the last 2 weeks of the experiment. Feed intake remained higher than the control level for 3 weeks in the S1 group and 4 weeks in the S2 group. Growth efficiency was not significantly different among the three groups in any of the weeks during re‐feeding. Compensatory responses in growth and especially feed intake tended to last longer than the recovery of body composition.

Topiramate reduces energy and fat gains in lean (Fa/?) and obese (fa/fa) Zucker rats.

This study examined the effects of topiramate (TPM), a novel neurotherapeutic agent reported to reduce body weight in humans, on the components of energy balance in female Zucker rats. A 2 x 3 factorial experiment was performed in which two cohorts of Zucker rats differing in their phenotype (phenotype: lean, Fa/?; obese, fa/fa) were each divided into three groups defined by the dose of TPM administered (dose: TPM 0, vehicle; TPM 15, 15 mg/kg; TPM 60, 60 mg/kg). The reduction in body weight gain induced by TPM in both lean and obese rats reflected a decrease in total body energy gain, which was more evident in obese than in lean rats. Whereas TPM administration did not influence the intake of digestible energy in lean rats, it induced a reduction in food intake in obese animals. In lean, but not in obese rats, apparent energy expenditure (as calculated by the difference between energy intake and energy gain) was higher in rats treated with TPM than in animals administered the vehicle. The low dose of TPM decreased fat gain (with emphasis on subcutaneous fat) without affecting protein gain, whereas the high dose of the drug induced a reduction in both fat and protein gains. The effects of TPM on muscle and fat depot weights were representative of the global effects of TPM on whole body fat and protein gains. The calculated energetic efficiency (energy gain/energy intake) was decreased in both lean and obese rats after TPM treatment. TPM dose independently reduced hyperinsulinemia of obese rats, but it did not alter insulinemia of lean animals. The present results provide sound evidence for the ability of TPM to reduce fat and energy gains through reducing energetic efficiency in both lean and obese Zucker rats.

Stimulation of oxygen consumption following addition of lipid substrates in liver and skeletal muscle from rats fed a high-fat diet

We studied hepatic and skeletal muscle metabolic activity in rats fed a high-fat diet. Rats were fed a low-fat or high-fat diet for 15 days. At the end of the experimental period, full energy-balance determinations together with serum free triiodothyronine (FT 3), leptin, and free fatty acid (FFA) measurements were performed. In addition, we assessed fatty acid—stimulated oxygen consumption in perfused liver and in skeletal muscle homogenate. Rats fed a high-fat diet showed a significant increase in energy intake but no variation in body energy gain, due to a significant increase in energy expenditure. Serum FT 3 and FFA levels significantly increased in rats fed a high-fat diet versus rats fed a low-fat diet, while no variation was found in serum leptin levels. Perfused livers and skeletal muscle homogenates from rats fed a high-fat diet exhibited a significant increase in fatty acid-stimulated oxygen consumption. Our results suggest that the enhanced fatty acid oxidation rates in liver and skeletal muscle contribute to the maintenance of fat balance in response to increased fat intake, preventing excess fat deposition.

Diet composition affects weight gain, adiposity and blood parameters in healthy human volunteers

This study examined the effect of diet composition on weight gain and body composition during a controlled overfeeding program. In weight reducing regimens, the body is energy blind and dietary energy rather than diet composition appears to be the greatest determinant of changes in weight and body composition. However, in overfeeding, both diet composition and excess energy intake are being implicated in obesity. Sixteen healthy adult subjects were overfed, 40% above their maintenance energy requirements, diets high in fat (50%) or carbohydrates (CHO) (60%) for a period of 4 weeks. Eight subjects were assigned to each of the experimental diets. Body weight, body composition, adiposity, serum lipids, insulin and glucose were measured in all subjects before and at the end of the feeding period. An Excess Energy Efficiency Factor (EEEF) was calculated as body energy gain per excess dietary energy. Results showed that adiposity was significantly higher in the high fat as compared to the high CHO fed group. EEEF was higher on the high fat as compared to high CHO diet. HDL-cholesterol was higher in subjects consuming the high fat as compared to those on the high CHO diet. This study shows that under conditions of excess energy intake, a high fat diet is more efficient in increasing adiposity and fat deposition as compared to high carbohydrate diet. The relative efficiency of macronutrients on body composition when fed at maintenance energy requirements remains to be investigated.

Growth and feeding responses of a hatchery population of brown trout (Salmo trutta L.) at low temperatures

Abstract— Feed intake, specific growth rate and changes in body composition were studied in age 1+ (140‐190 g) brown trout (Salmo trutta L.) reared at three temperatures (2, 4 and 6°C) under continuous light conditions. Feed in take increased from 35.7 kJ‐kg−1.day−1 at 2°C to 95.7 kJ‐kg−1‐day−1 at 6°C, and the growth rate increased from 0.19%‐day−1 to 0.42%‐day−1 over the same temperature range. The estimated lower temperature limits for feeding and growth were slightly above 0°C. For all groups of fish, the majority (about 75%) of the weight gain comprised water and protein, but lipid deposition tended to increase with increasing temperature. The deposition of lipid accounted for about 50% of the body energy gain at all temperatures.

Feed intake, growth rate and body composition of juvenile Baltic salmon exposed to different constant temperatures

Feed intake, specific growth rate and changes in body composition of age 1+ and 2+ Baltic salmon, Salmo salar L, were studied for fish held under constant temperature conditions. The 1+ fish (60 g) were reared for 6 weeks at 11, 15, 17, 19 or 23 °C and 2+ fish (250 g) were held at 15 °C. Feed intake of 1+ salmon increased from 176 kJ kg-1 day-1 at 11 °C to 275 kJ kg-1 day-1 at 17 °C and decreased to 229 kJ kg-1 day-1 at 23 °C. Specific growth rate increased from 1.18% day-1 at 11 °C to 1.59% day-1 at 15 °C and decreased to 0.56% day-1 at 23 °C. Optimum temperatures for feed intake and growth were estimated at 17.8 °C and 15.6 °C, respectively, and estimated upper thermal limits for feeding and growth were 29.0 °C and 24.1 °C, respectively. Models for feed intake and growth rate in relation to temperature and fish size are presented. The utilization efficiency of ingested energy decreased from 57% at 11 °C to 22% at 23 °C. For all groups of 1+ fish, most (approximately 86%) of the weight gain consisted of water. Lipid deposition accounted for about 52% of the body energy gain irrespective of rearing temperature.

Effect of low temperature on feed intake, growth rate and body composition of juvenile Baltic salmon.

Feed intake, specific growth rate and changes in body composition were studied in juvenile (140-170 g) Baltic salmon, Salmo salar, reared at three temperatures (2, 4 and 6 °C) under continuous light conditions. Feed intake increased from 20.4 kJ kg-1 day-1 at 2 °C to 63.8 kJ kg-1 day-1 at 6 °C, and growth rate increased from 0.10% day-1 to 0.37% day-1 over the same temperature interval. The estimated lower temperature limits for feeding and growth were approximately 0.35 °C and 0.6 °C, respectively. Amongst fish reared at 2 °C the majority (86%) of the weight gain consisted of water and protein, and these fish deposited very little lipid. Lipid deposition increased amongst the groups of fish held at the higher temperatures, and amongst the salmon reared at 6 °C lipid accounted for 43% of the body energy gain.