Dietary Self-selection Research Articles

Nile tilapia and gilthead seabream dietary self-selection of alternative feeds

Classical assessments of new fish feeds are anthropocentric, focusing mainly on growth. Although this methodology is accurate, it does not consider the fish’ perspective. This study aimed to investigate the behavioural responses and feed preferences of Nile tilapia (Oreochromis niloticus) and gilthead seabream (Sparus aurata) through a self-selection trial using self-feeders. Both species were offered three feeds: a control (PD) commercial-like feed and two diets (ORG1 and ORG2) formulated with different inclusions of alternative ingredients to address some of the current environmental concerns and/or ethical issues often associated with commercial formulations. Three groups of tilapia with an average weight of 163.0 g ± 4.3 g (mean ± SD) and four groups of seabreams with 174.7 g ± 27.0 g were tested. Tilapia exhibited a preference for ORG2 (46.5%), influenced by the sensory properties of the feed and post-ingestion signals. Seabream did not show a preference for any feed. These findings highlight the effectiveness of self-selection experiments in allowing fish to express their feeding behaviour and preferences. Therefore, this approach should be considered in the initial screening and design of new aquaculture feeds and ingredients.

Crickets (Gryllus Bimaculatus) using food waste usefulness of self-selection feed design method through each growth stage

Abstract In this study, a self-selected feed design was conducted for Japanese food wastes, considering the macronutrients (protein, lipid, carbohydrate) and six feed options and three options for vegetable wastes, and performance was compared with commercial diet to determine the usefulness of the feed design method and the possibility of using food waste in Japan were examined by comparing the performance of the feed design method with commercial diet. Data on self-selection diet design for crickets at different growth stages were obtained to determine the differences in feed consumption rates and nutrient requirements among stages. The results showed that it is possible to achieve cricket weight and feed conversion efficiencies (0.5-0.8) comparable to those of commercial diets using food residues when macro-nutrients are considered, and abundant options are provided. On the other hand, the use of only vegetable wastes resulted in lower cricket weight and higher feed conversion efficiency (0.8-1.4). Based on feed consumption rates, bread bran, rice bran, and fish meal were found to be suitable feeds among Japanese food waste for production in all growth stages, while bean curd and sake less were found to be suitable for production in some growth stages. Data obtained from self-selections separated by growth stage revealed that the percentage of feed consumption varied greatly among growth stages, being about 50-68% in the late growth stage. Percentages of macronutrients and micronutrients were also found to vary by growth stage. Protein percentages were found to be higher in the second week after hatching. Lipids were highest in the first week and decreased thereafter. Crude fiber was lowest in the fourth week. Ash content did not change significantly at all stages. This research is the first attempt at self-selection of crickets in different growth stages, and the data obtained can contribute to feed design.

Voluntary physical activity modulates self-selection of a high-caloric choice diet in male Wistar rats

Physical exercise training has been positioned as a behavioral strategy to prevent or alleviate obesity via promotion of energy expenditure as well as modulation of energy intake resulting from changes in dietary preference. Brain adaptations underlying the latter process are incompletely understood. Voluntary wheel running (VWR) is a self-reinforcing rodent paradigm that mimics aspects of human physical exercise training. Behavioral and mechanistic insight from such fundamental studies can help optimize therapies that improve body weight and metabolic health based on physical exercise training in humans.To assess the effects of VWR on dietary self-selection, male Wistar rats were given access to a two-component “no-choice” control diet (CD; consisting of prefabricated nutritionally complete pellets and a bottle with tap water) or a four-component free-choice high-fat high-sucrose diet (fc-HFHSD; consisting of a container with prefabricated nutritionally complete pellets, a dish with beef tallow, a bottle with tap water, and a bottle with 30% sucrose solution). Metabolic parameters and baseline dietary self-selection behavior during sedentary (SED) housing were measured for 21 days, after which half of the animals were allowed to run on a vertical running wheel (VWR) for another 30 days. This resulted in four experimental groups (SEDCD, SEDfc-HFHSD, VWRCD, and VWRfc-HFHSD). Gene expression of opioid and dopamine neurotransmission components, which are associated with dietary self-selection, was assessed in the lateral hypothalamus (LH) and nucleus accumbens (NAc), two brain regions involved in reward-related behavior, following 51 and 30 days of diet consumption and VWR, respectively.Compared to CD controls, consumption of fc-HFHSD before and during VWR did not alter total running distances. VWR and fc-HFHSD had opposite effects on body weight gain and terminal fat mass. VWR transiently lowered caloric intake and increased and decreased terminal adrenal and thymus mass, respectively, independent of diet. VWR during fc-HFHSD consumption consistently increased CD self-selection, had an acute negative effect on fat self-selection, and a delayed negative effect on sucrose solution self-selection compared to SED controls. Gene expression of opioid and dopamine neurotransmission components in LH and NAc were unaltered by fc-HFHSD or VWR. We conclude that VWR modulates fc-HFHSD component self-selection in a time-dependent manner in male Wistar rats.

Plasma FGF21 concentrations and spontaneous self-selection of protein suggest that 15% protein in the diet may not be enough for male adult rats

Protein requirement has been determined at 10%-15% energy. Under dietary self-selection, rats ingest 25%-30% energy as protein and regulate FGF21 (a hormone signaling protein deficiency) to levels lower than those measured with a 15% protein (15P) diet. Our hypothesis is that if a 15P diet was indeed sufficient to ensure protein homeostasis, it is probably a too low protein level to ensure optimal energy homeostasis. Adult male Wistar rats were used in this study. The first objective was to determine the changes in food intake, body composition, and plasma FGF21, IGF-1, and PYY concentrations in rats fed 8P, 15P, 30P, 40P, or 50P diets. The second was to determine whether the FGF21 levels measured in the rats were related to spontaneous protein intake. Rats were fed a 15P diet and then allowed to choose between a protein diet and a protein-free diet. Food intake and body weight were measured throughout the experiments. Body composition was determined at different experimental stages. Plasma samples were collected to measure FGF21, IGF-1, and PYY concentrations. A 15P diet appears to result in higher growth than that observed with the 30P, 40P, and 50P diets. However, the 15P diet probably does not provide optimal progression of body composition owing to a tendency of 15P rats to fix more fat and energy in the body. The variable and higher concentrations of FGF21 in the 15P diet suggest a deficit in protein intake, but this does not appear to be a parameter reflecting the adequacy of protein intake relative to individual protein requirements.NEW & NOTEWORTHY Under dietary self-selection, rats choose to ingest 25%-30% of energy as protein, a value higher than the protein requirement (10%-15%). According to our results, this higher spontaneous intake reflects the fact that rats fed a 15% protein diet, compared with high-protein diets, tend to bind more fat and have higher concentrations of FGF21, a hormone signaling protein deficiency. A 15% protein diet appears to be sufficient for protein homeostasis but not for optimal energy homeostasis.

Comparison of Diet Preferences of Laboratory-Reared and Apartment-Collected German Cockroaches.

The German cockroach, Blattella germanica (L.) (Blattodea: Ectobiidae), is a common pest of human-built structures worldwide. German cockroaches are generalist omnivores able to survive on a wide variety of foods. A number of studies have concluded that laboratory-reared B. germanica self-select diets with an approximate 1P:3C (protein-to-carbohydrate) ratio. We predicted that field-collected insects would exhibit more variable dietary preferences, related to the wide-ranging quality, quantity, and patchiness of foods available to them. We compared diet self-selection of B. germanica within apartments and in the laboratory by offering them a choice of two complementary diets with 1P:1C and 1P:11C ratios. We observed high variation in the population-level self-selection of these diets among individual apartment sites as well as among various life stages tested in laboratory-based assays. Significant differences between populations in various apartments as well as between populations maintained in the laboratory suggested that factors beyond temporary food scarcity influence diet choice. Nevertheless, we found significant correlations between the amounts of diets ingested by cockroaches in apartments and cockroaches from the same populations assayed in the laboratory, as well as between males, females, and nymphs from these populations. These findings suggest that females, males, and nymphs within apartments adapt to the local conditions and convergently prefer similar amounts of food of similar dietary protein content.

Rats Self-Select a Constant Protein-to-Carbohydrate Ratio Rather Than a Constant Protein-to-Energy Ratio and Have Low Plasma FGF21 Concentrations.

Under dietary self-selection (DSS), rats ingest 25-30% of energy as protein. This high level appears to be explained by metabolic benefits related to reduced carbohydrate dependence and associated pathologies. However, the mechanisms underlying these choices remain largely misunderstood. The aim was to test the hypothesis that in a DSS model, rats select a protein-to-energy (PE) ratio to maintain the protein-to-carbohydrate (PC) ratio constant and that fibroblast growth factor 21 (FGF21) is involved in this response. Adult male Wistar rats were used in 3 experiments. The first was to determine whether the PE ratio was influenced by changes in carbohydrate content. The second was to test whether the PE ratio was defended with a modified DSS model. The third was to determine whether the selected PE ratio was of metabolic interest compared with a standard 15% protein diet. Food intake, body weight, and energy expenditure were measured. After 3 wk, plasma was sampled and rats were killed to determine body composition and gene expression. Statistical analyses were mainly done by ANOVA tests and correlation tests. The selected PE ratio increased from 20% to 35% when the carbohydrate content of the protein-free diet increased from 30% to 75% (R2 = 0.56; P<10-6). Consequently, the PC ratio was constant (70%) in all groups (P=0.18). In self-selecting rats, plasma FGF21 concentrations were 3 times lower than in rats fed the 5% protein diet (P<10-4) and similar to those in rats fed a 30% diet. This study showed that self-selecting rats established PE ratios larger than those considered sufficient to achieve optimal growth in adult rats (10-15%), and the ratios were highly dependent on carbohydrates, apparently with the aim of maintaining a constant and high PC ratio. This was associated with a minimization of plasma FGF21.

Self-selection of food ingredients and agricultural by-products by the house cricket, Acheta domesticus (Orthoptera: Gryllidae): A holistic approach to develop optimized diets

The house cricket, Acheta domesticus L. (Orthoptera: Gryllidae) is one of the most important species of industrialized insects in the United States. Within the past five years the market of cricket powder as a food ingredient has been growing with increasing consumer interest on more sustainable sources of food. However, high labor costs of cricket production and high prices of cricket feed formulations result in cricket powder market prices much higher than other protein-rich food ingredients, making cricket powder only competitive within the novelty food market. In this study new diets formulated using by-products were developed using dietary self-selection followed by regression analysis. Crickets selected among seven different combinations of ingredients. Consumption ratios of food ingredients and by-products were used to determine macro and micro-nutrient intake. Regression analysis was used to determine the individual nutrient intake effect on cricket biomass production. Intake of vitamin C, sterol, manganese, and vitamins B1 and B5 had the most significant impact on live biomass production. Four diets were formulated based on this information and compared with a reference (Patton's 13) and a commercial diet. Although, crickets reared on Patton's diet 13 produced the most dry-weight biomass and developed the fastest, diet 4 (consisting of 92% by-products) generated the most profit (with a cost of $0.39 USD per kg) after an economic analysis that did not include the commercial formulation. Dry-weight biomass production was not significantly different among the four new diets and the commercial diet. This study demonstrated the value of dietary self-selection studies in developing oligidic insect diets and in studies of insect nutrition. This is the first such study involving farmed edible crickets and agricultural by-products. Four new cricket diet formulations contain between 62 and 92% agricultural by-products are included.

Perinatal exposure of rats to a maternal diet with varying protein quantity and quality affects the risk of overweight in female adult offspring

The maternal protein diet during the perinatal period can program the health of adult offspring. This study in rats evaluated the effects of protein quantity and quality in the maternal diet during gestation and lactation on weight and adiposity in female offspring. Six groups of dams were fed a high-protein (HP; 47% protein) or normal-protein (NP; 19% protein) isocaloric diet during gestation (G) using either cow's milk (M), pea (P) or turkey (T) proteins. During lactation, all dams received the NP diet (protein source unchanged). From postnatal day (PND) 28 until PND70, female pups (n=8) from the dam milk groups were exposed to either an NP milk diet (NPMW) or to dietary self-selection (DSS). All other pups were only exposed to DSS. The DSS design was a choice between five food cups containing HPM, HPP, HPT, carbohydrates or lipids. The weights and food intakes of the animals were recorded throughout the study, and samples from offspring were collected on PND70. During the lactation and postweaning periods, body weight was lower in the pea and turkey groups (NPG and HPG) versus the milk group (P<.0001). DSS groups increased their total energy and fat intakes compared to the NPMW group (P<.0001). In all HPG groups, total adipose tissue was increased (P=.03) associated with higher fasting plasma leptin (P<.05). These results suggest that the maternal protein source impacted offspring body weight and that protein excess during gestation, irrespective of its source, increased the risk of adiposity development in female adult offspring.

Regulation of macronutrient intake in termites: A dietary self-selection experiment

Many animals have been shown to select among nutritionally complementary foods to reach a specific balance of nutrients that optimizes key life history traits. Nutritional ecology theory, however, predicts that an animal with a diet that is very stable in its composition, and with nutritional requirements that do not vary in their balance through time, would not need to display such mechanisms of regulation. Here we use the Australian termite Nasutitermes exitiosus as a model to test this prediction for the first time. We used the nutritional geometric framework to investigate the regulation of carbohydrate and protein, as well as the effects on foraging behaviour of protein type and group caste composition and size. Our results support the prediction of nutritional ecology, as termites failed to actively defend a well-defined macronutrient ratio. Termites maintained food collection relatively constant across protein type and group composition, and only appear to vary their collection by avoiding diets too rich in protein.

Egg production and quality of local female chicken by dietary self-selection reared under semi-scavenging system in the tropics

The feeding standard for local chicken breeds in Indonesia has not been published yet. The present study were aimed to measure egg production and quality while estimating the ME and CP needs during production for local female chickens reared under semi-scavenging system in the tropics (Indonesia) through dietary self-selection. A total of 138 twenty two week-old chicks were randomly distributed into 12 sheltered pens, 10-14 birds each. Two feeding methods (control and self-selection) were assigned to pens, so each treatment consisted of 6 replicates. The control group received a control diet complying with the Hy-line Brown Nutrient Requirements Standard, whereas the self-selection group had access to the control and four other diets (high energy-high protein, low protein-high energy, high protein-low energy, and low protein-low energy diet). Feeds and drinking water were provided ad libitum to 53 weeks of age. Feed consumption (FC), CP intake, ME intake, concentration of dietary CP and ME and egg production were recorded weekly. Egg quality was measured three times. Daily temperature and relative humidity in the morning (07:00), noon (12:00), and afternoon (17:00) were 21.8 to 28.1°C and 46 to 88%; 24.7 to 34.5°C and 35 to 72%; and 23.5 to 34.5°C and 36 to 80%, respectively. Data were analyzed using Proc Mixed of SAS, but egg quality was analyzed by ANOVA. The results showed that feeding method had apparent effect on CP intake (P=0.018) and ME intake, dietary concentration of CP and ME, egg production (P<0.001) but not on FC. The effect of week and feeding method by week interaction were also very significant for all performance, except egg production was not affected with feeding method by week interaction. Weekly CP and ME intake of the self-selection group were greater than those of the control (105.8 vs. 101.3 g/bird; P=0.018 and 1,709 vs. 1,575 kcal/bird; (P<0.001), respectively). Dietary concentrations of CP and ME in the self-selection group was higher (P<0.001) than those in the control group (189.3 vs. 180.7 g/kg and 3,053 vs. 2,810 kcal/kg, respectively). Egg production of the self-selection group was higher (P<0.001) than those of the control (60.5% vs. 55%). Over all, egg quality (eggshell thickness, shell strength, shell weight, egg weight, Hmm, color, compare, HU, and yolk weight) was similar, except color and compare were higher in choice-fed birds when they grew older. Local female chickens were able to select diets to adjust their nutrient requirements by selecting more of an energy-rich diet and less of a protein-rich diet. CP and ME requirement by local female chickens were more likely greater than the current formulated for them in order to increase egg production.

Varying Protein Quantity and Quality in the Maternal Diet During the Perinatal Period Affects Growth and Adiposity Risk in Female Adult Offspring in Rats (OR09-03-19)

ObjectivesMaternal diet in the perinatal period can program health of adult offspring. This study evaluates the consequences of maternal dietary protein quality and quantity during gestation and lactation on overweight risk in female offspring subjected to dietary self-selection (DSS). MethodsSix groups of rat dams were fed a high-protein (HP; 47% protein) or normal protein (NP; 19% protein) isocaloric diet during gestation. Protein sources of HP and NP diets were either milk (M), pea (P), or turkey (T)-derived. During lactation, dams were fed NP diet containing the protein source as fed during pregnancy. From postnatal day (PND) 28 to 70, pups (n = 8 per group) were exposed to DSS with a choice between five cups containing either: HP-M, HP-P, HP-T diets, or only carbohydrates or only lipids. Pups’ weight gain and food intake were recorded daily. Body composition, fasting plasma insulin and leptin levels were assessed at the end of the study (PND70). ResultsDuring lactation, pups’ weight gain was lower in the “turkey and pea” compared to “milk” group (P < 0.0001), resulting in a lower weight gain in the “pea” compared to “milk” group at the end of the lactation period (PND28; P < 0.0001). Body weight gain from PND28 to 70 was also lower in the “pea and turkey “compared to “milk” group (P < 0.0001). Total food intake throughout the postweaning period, was lower in the “pea and turkey” compared to “milk” group (P < 0.05). At PND70, body composition was affected by (i) the maternal protein source showing a lower adipose tissue weight in the “pea and turkey” compared to “milk” group (P = 0.01), but also by (ii) the maternal protein quantity showing increased adipose tissue weight (≥16%) in HP compared to NP gestation groups (P = 0.03) (figure 1), regardless of the protein source in the maternal diet. In accordance with the increased adipose tissue weight in HP groups, fasting plasma leptin levels were significantly higher in HP compared to NP gestation groups (P < 0.05). Plasma insulin levels were not affected. ConclusionsDietary protein source during gestation and lactation directly affected weight gain of the offspring after weaning and at adulthood. HP diet during gestation resulted in a higher adiposity in the offspring, independent of the protein source. Funding SourcesThis thesis work was partly funded by Danone Nutricia Research. Supporting Tables, Images and/or Graphs▪

Maternal High-Protein Diet during Pregnancy Modifies Rat Offspring Body Weight and Insulin Signalling but Not Macronutrient Preference in Adulthood.

Diet of mothers during gestation may impact offspring phenotype. This study evaluated the consequences of a maternal High-Protein (HP) diet during gestation on food preferences and phenotypic characteristics in adult rat offspring. Dams were fed a HP or a Normal-Protein (NP) isocaloric diet during gestation only. Weaned female pups were divided into 3 diet groups: NP control or one of two dietary self-selection (DSS) conditions. In DSS1, offspring had a free choice between proteins (100%) or a mix of carbohydrates (88%) and lipids (12%). In DSS2, the choice was between proteins (100%), carbohydrate (100%) or lipids (100%). DSS2 groups consumed more of their energy from protein and lipids, with a decreased carbohydrate intake (p < 0.0001) compared to NP groups, regardless of the maternal diet. Offspring from HP gestation dams fed the DSS2 diet (HPDSS2) had a 41.2% increase of total adiposity compared to NPDSS2 (p < 0.03). Liver Insulin receptor and Insulin substrate receptor 1 expression was decreased in offspring from HP compared to NP gestation dams. These results showed the specific effects of DSS and maternal diet and data suggested that adult, female offspring exposed to a maternal HP diet during foetal life were more prone to adiposity development, in response to postweaning food conditions.

Daily self-feeding activity rhythms and dietary self-selection of pirarucu (Arapaima gigas)

Daily feeding rhythms and the ability of pirarucu (Arapaima gigas) to compose a balanced diet through macronutrient self-selection were evaluated. Twelve fish (1573.3±74.4g) were distributed in six tanks of 250l, two fish per tank. First, three experimental diets were prepared using an incomplete mixture of macronutrients (75%protein/25%carbohydrate-PC, 75%protein/25%fat-PF and 10% protein/45%fat/45%carbohydrate-PFC). These diets were provided to fish through a self-feeding system connected to a computer to record feeding activity. After this procedure, fish were challenged with a 50% protein dilution (diets: PC50 and PF50). The results showed that pirarucu exhibited a strict diurnal feeding pattern with 95.4% of daily feeding activity observed in the daytime. Fish selected 56.3% P, 24.2% C, 19.5% F, and consumed 150–151kJ/kg BW/day of energy. After protein dilution, fish sustained energy intake by increasing the consumption of PC50 and PF50 to maintain the target protein intake of the previous stage. When fish were protein-restricted, they failed to sustain previous energy intake. These findings can be used to design feeding regimes and for formulating aquafeed for pirarucu. Statement of relevanceThe use of an automatic feeder system activated by the fish could allow the animal to feed at their preferred time and hence reduces waste and improve the intake. Studies that consider the fish preference as a guide in designing diets can provide data on mechanisms of nutrient intake regulation for the development of aquafeeds for new species with potential for aquaculture.

Obesity‐prone high‐fat fed rats reduce caloric intake and adiposity and gain more fat‐free mass when allowed to separate protein from carbohydrate/fat intake

Dietary fat is among the factors often considered responsible for the high prevalence of adiposity. Both genetic and epigenetic factors influence who in a population will develop adiposity and it is established that humans as well as rodent models are not uniformly sensitive to adiposity gain under high fat diets.In addition it is also recognized that when placed on dietary self‐selection (DSS) conditions, most species are generally able to select an adequate diet for growth and maintenance. In most cases, caloric intake and body weight gain suggest that DSS is closely related to nutritional and physiological requirements. In one previous studies (1), when shifted from a control (low‐fat) mixed diets to DSS rats spontaneously increased protein and strongly decreased caloric intake (−40%) together with preservation of a normal growth which suggested that before DSS rats ate more food in order to increase protein intake.The present study tested the hypothesis that in rats fed a high fat diet (HFD), and particularly in individuals prone to adiposity gain (“fat sensitive”, FS, as opposed to “resistant”, FR), a prioritisation of maintaining protein intake could be involved in the excess energy consumption and hence obesity when fed diet with a protein content considered as too low by the animal. For that purpose, male Wistar rats first received three weeks of HFD (by energy ‐ Protein 15%, Fat 42%, Carbohydrate 42%) under which they were characterised as being FS or FR and then were switched to the same HF diet but in which protein was available separately from the carbohydrate/fat mixture (DSS).The results showed that under this DSS regimen, FR as well as FS rats maintained a similar intake of protein whereas intakes of fat and carbohydrate were reduced by 50%. Overall intake was: protein 27%, carbohydrate 37%, and fat 37%, ie caloric intake remained high in fat. All rats separated in time the ingestion of protein and that of the carbohydrate/fat mix, i.e. avoided to mix again the 3 macronutrients. In both FR and FS rats, adiposity gain was prevented and, in FS rats only, fat free mass gain was increased. Analysis of mRNA showed that enzymes expression of genes coding for lipogenesis was larger in liver and adipose tissue of FS rats.These results show that high‐fat fed rats were able to strongly reduce food intake and adiposity gain through macronutrient selection and that this response occurred in FS rats despite maintenance of mechanisms favoring fat storage.

Dietary self-selection in fish: a new approach to studying fish nutrition and feeding behavior

The principles of modern aquaculture encourage the development of fish feeds containing low fish meal content and several types of plant ingredients plus nutrients to avoid depleting global fish stocks and to reduce costs. However, food constituents can affect animal nutrition and feeding behavior, so the effect of different diets on fish behavior and growth needs to be understood to optimize the use of nutrients and to improve fish welfare. The development of multiple-choice self-feeding systems led to a new perspective for investigating these issues in aquaculture species. Our purpose with this review is to summarize the information that has been published to date on this topic and to identify gaps in knowledge where research is needed. Key subjects are assessed under the following major headings: How do we study dietary selection in fish? What food signals do fish use to choose the right diet? and How do fish respond to food challenges? The present review will provide a picture of the main results obtained to date in these studies in aquaculture fish species, as well as perspectives for future research in the field.

A Study of the self-selection of postoperative diets after gastrectomy

A Study of the self-selection of postoperative diets after gastrectomy

QTLs influencing carbohydrate and fat choice in a LOU/CxFischer 344 F2 rat population

Individual differences in macronutrient selection, particularly fat and carbohydrate, and associated body weight gain are partly inherited as polygenic traits, but the potential genetic pathways are unknown. To give an overview of the Quantitative Trait Loci (QTLs) and candidate gene pathways influencing these differences in rat was aimed in this study. To that end, F2 rats obtained from the crossbreeding between LOU/C and Fischer 344 rat strains to diet self-selection during 3 weeks were submitted. A genome scan was conducted with microsatellite markers covering evenly the whole genome. Genotypes and phenotypes were analyzed separately in male and female F2 rats by multiple interval mapping. Then, lists of candidate genes were treated by the Ingenuity Pathway software to propose gene pathways involved in our phenotypes. Among numerous others, a QTL on chromosome 12 that influences body weight gain, and fat and carbohydrate choices in the LOU/C x Fischer 344 F2 rat population was found. This locus contains notably the acyl-co-A dehydrogenase gene. A strong genetic determinism and complex pathways involving numerous candidate genes and processes, notably in accordance with the metabolic theory of feeding behavior control were found.

Self-selection of diets with different contents of arachidonic acid by Senegalese sole (Solea senegalensis) broodstock

Senegalese sole (Solea senegalensis) failed to reproduce and spawn viable eggs when bred and reared in captivity (first generation G1 cultured broodstock). Cultured sole were also shown to have significantly lower levels of arachidonic fatty acid (20:4n−6, ARA) in reproductive tissues compared to wild counterparts. However, to date no information about ARA requirements of Senegalese sole broodstock (wild or cultured) has been available. The present study was designed to determine dietary ARA preferences of adult G1 Senegalese sole by the use of automated demand feeders. For this purpose, three groups of 16 (eight females and eight males) G1 fish were offered to select between two diets, one with high (6.0% of total fatty acids, TFA) and another with low (0.7% TFA) ARA content. The experiment was conducted for 16 consecutive months. The results revealed that Senegalese sole changed the preference for ARA during the year, in correlation with the seasonal water temperature (r2=0.7), and with periods of high and low demand of total food ingested. Thus, a high ARA (3.9% TFA) selection was observed in summer and early-autumn, whereas low ARA (2.2% TFA) selection occurred in winter. The average ARA demanded during the whole year was 3.0% TFA, with a resultant high level of ARA in the tissues of the fish; especially in male testis (8.8% TFA). These results should be considered when formulating seasonal diets to suit sole broodstock preferences in ARA in intensive aquaculture.

Dietary selection by gilthead sea bream (Sparus aurata) provided with unbalanced mixed-macronutrient feeds dispensed from self-feeders

We investigated dietary self-selection in gilthead sea bream using a multiple-choice self-feeding system. To this end, five groups of 15 fish (154g BW) were distributed among 500-l tanks and allowed to self-feed from 3 self-feeders, each of which distributed feeds composed of combinations of macronutrients. Three different selection ranges of protein (P), carbohydrate (C) and fat (F) (expressed as percentage of total macronutrients) were tested: in phase 1, PF (75%–25%, respectively), PC (75%–25%) and CF (85%–15%); in phase 2, PF (60%–40%), PC (75%–25%) and CF (60%–40%); and in phase 3, PF (60%–40%), PCF (20%–50%–30%) and PC (90%–10%). In addition, the effect of P deprivation on energy intake was tested. The results revealed that, despite the different selection ranges in each phase, the macronutrient composition of the selected diets did not differ significantly during the experiments, being on average 63.7±0.6% P, 15.5±1.7% F and 20.6±1.15% C. When sea bream were restricted to self-feeding on a protein-free diet for 10days, and were only given the CF (60%–40%) diet, the fish sustained their average energy intake (260.0±37.7kJ/kg BW/day), which did not differ statistically from the average energy intake during the previous three experimental phases (284.6±26.9kJ/kg BW/day). In conclusion, sea bream were able to compose and defend a balanced diet by selecting from three incomplete diets, and the fish were also able to maintain their energy intake for a short period of time when allowed to self-feed on a protein-free diet.

Dietary self-selection by broilers at normal and high temperature changes feed intake behavior, nutrient intake, and performance

Self-selection assumes that at high ambient temperature, birds are able to select a diet from different sources to minimize the heat load associated with the ingested nutrient metabolism. The objective was to test the hypothesis that young chickens are able to compose an adequate ration by adjusting dietary nutrient intake from 3 different diets that vary in energy and in protein contents from a cafeteria system at high temperature (HT; 31–32°C) and at normal temperature (NT; 31–21°C). Night temperature was set at 25°C at HT and at 18°C at NT and 12 h dark:12 h light. Control birds were fed a standard control diet (CP: 215 g/kg; ME: 2,895 kcal/kg) for broiler chickens. The choice-fed birds could choose between the control diet, a high-protein diet (CP: 299 g/kg; ME: 2,780 kcal/kg), and a high-energy diet (CP: 150.7 g/kg; ME: 3,241 kcal/kg). The diets had similar pellet size and color. Birds had access to each diet in a separate feeding trough from 1 to 42 d of age. Results showed that broilers spent 3.3% more time eating at NT than at HT and showed 42% more panting behavior at HT than at NT. High temperature decreased feed intake, protein intake, energy intake, and BW gain. Choice-fed birds had similar feed intake and BW gain, 14% lower protein intake, and 6.4% higher energy intake than control-fed birds. Body temperature and heterophil/lymphocyte ratio were higher at HT than at NT. Water intake was 8% higher in control-fed birds than in choice-fed birds but similar at both temperature regimens. It can be concluded that broilers can compose a diet by selecting less protein but higher energy density from different diets compared with the control. Choice-fed birds had similar feed efficiency as control-fed birds at HT, indicating similar body composition for both groups. Extra energy intake of choice-fed birds at HT was used for panting activity.