Biomedical subjects

J A Madrid

Publications and source records attributed to J A Madrid.

At least 19 recordsLinked to original sources

PubMed2006

Feeding entrainment of locomotor activity rhythms, digestive enzymes and neuroendocrine factors in goldfish.

The existence of food anticipatory activity (FAA) in animals subjected to daily feeding schedules seems to be mediated by a feeding-entrainable oscillator (FEO). Such an FEO may help in anticipating meal time and so optimizing food acquisition and nutrient utilization. In this study we investigated the existence of FAA and whether digestive enzymes, plasma cortisol, hypothalamic NPY and gastrointestinal tract (GIT) and plasma melatonin were entrained by periodic feeding in goldfish. We observed that periodically fed goldfish showed FAA in locomotor activity as well as in amylase and NPY. Alkaline protease and GIT melatonin were higher after feeding, whereas plasma cortisol levels were reduced. Plasma melatonin remained unmodified before and after meal time. These results suggested that scheduled feeding entrained both behavioral and certain physiological patterns in goldfish, FAA being of adaptive value to anticipate a meal and prepare the digestive physiology of fish.

Activity Cycles↗

PubMed2006

Response of plasma and gastrointestinal melatonin, plasma cortisol and activity rhythms of European sea bass (Dicentrarchus labrax) to dietary supplementation with tryptophan and melatonin.

Melatonin is an effective antioxidant, immunostimulant, gonadal maturating regulator and antistress indoleamine that may be potentially useful for fish farmers. We have explored two possible ways of increasing plasma melatonin levels through the diet: direct melatonin supplementation (ME diet) and supplementation with the melatonin precursor tryptophan (TRP diet). To this end, a group of sea bass was fed a commercial diet (STD diet) at a regular time for 16 days, after which plasma, intestine, and bile samples were taken at four different time points: 120 min before, and 15, 180 and 480 min after feeding. Locomotor activity, intestinal and biliary melatonin, and plasma melatonin, serotonin and cortisol levels were measured. This same sampling process and analyses were also carried out after feeding sea bass TRP diet or ME diet for 1 week. Our results show that melatonin, but not tryptophan supplementation of the diet increases plasma, intestine and bile levels of melatonin. Plasma serotonin levels, on the other hand, were increased by dietary tryptophan, but not by melatonin, confirming the availability of supplemented tryptophan for serotonin synthesis. Both treatments were equally effective in reducing the high cortisol levels observed with the STD diet.

Animals↗

PubMed2006

Influence of nutrient preload on encapsulated macronutrient selection in European sea bass.

The sea bass is a teleost that is able to regulate its energy intake by selecting from pure macronutrient sources, although the regulatory mechanisms involved in this selection are unknown. Nutrient preloads are known to reduce food intake and modify macronutrient selection patterns in mammals, but no information is available on its effects in fish. The aim of the present work was to determine the effect of orally administered macronutrient preloads of protein (P), fat (F) or carbohydrate (CH) on the subsequent macronutrient selection, using for the purpose feed consisting of CH, P or F packaged separately in gelatin capsules. The macronutrient preloads left the total food intake unaltered, but caused differential changes in the pattern of macronutrient selection. The CH preload increased the selection of CH (39%) and decreased that of P (20%), independently of the fish's previous nutritional preferences. The F preload induced an F increase (32%) and a P decrease (18%) in P-preferring fish, but not in F-preferring fish in which the macronutrient selection pattern remained unaffected. The P preload stimulated F selection by 42% in P-preferring fish, but left the macronutrient selection pattern unchanged in F-preferring fish. In conclusion, oral macronutrient preloads affected the pattern of macronutrient selection in fish, acting by post-ingestive mechanisms. The effect was influenced by the fish's previous nutritional preference and/or status, which could depend on its metabolic capacity.

Administration, Oral↗

PubMed2006

Macronutrient selection through post-ingestive signals in sharpsnout seabream fed gelatine capsules and challenged with protein dilution.

Sharpsnout seabream ability for macronutrient self-selection was studied using gelatine capsules containing pure macronutrients. In particular, the existence of non-oropharyngeal chemosensory pathways involved on protein (P), fat (F) and carbohydrate (CH) selection, as well as sharpsnout seabream response to dietary protein dilution were investigated. In a sequence of experimental phases, sharpsnout seabream were fed a pelleted complete diet, an encapsulated complete diet or a combination of separately encapsulated pure macronutrients. In order to induce associative learning, capsules containing a given macronutrient were paired with a particular colour. The animals composed a diet containing 62.7% P, 21.3% CH and 16.0% F, in terms of macronutrient percentage intake, and this selection pattern was maintained throughout all experimental phases. In a second experiment, individually kept sharpsnout seabream were challenged with protein dilution. After protein capsules were diluted (from 91.9% P to 56.3% P) with cellulose, the animals increased their protein intake to compensate for dilution in such a way that their energy intake was not significantly modified (17.4 kJ/100 g BW vs. 17.6 kJ/100 g BW after dilution). These results show that sharpsnout seabream feeding on encapsulated diets are able to select and maintain a particular diet composition, as well as sustain their energy intake, without using the diet's oropharyngeal chemosensory properties. Moreover, they were also able to maintain their protein intake after dilution, which highlights the importance of this macronutrient in this omnivorous species.

Animals↗

PubMed2006

Locomotor, feeding and melatonin daily rhythms in sharpsnout seabream (Diplodus puntazzo).

Sharpsnout seabream is a marine teleost of increasing interest for Mediterranean aquaculture, but there is still a lack of information regarding its circadian organization. In this study, we have investigated sharpsnout seabream locomotor activity, feeding and plasma melatonin daily rhythms under a 12:12-h LD cycle, as well as the persistence of locomotor activity circadian rhythmicity under constant light (LL) conditions. When submitted to an LD cycle, most sharpsnout seabream displayed a diurnal locomotor pattern, with an average 74% of activity recorded during daytime. However, along the experiment 40% of fish spontaneously changed their locomotor rhythm phasing and became nocturnal. Feeding behaviour, nevertheless, remained strictly diurnal in all cases, with 97% of food demands being made during the light period. Free-running locomotor rhythms were recorded in one third of the fish kept under LL. Daily plasma melatonin levels displayed a rhythmic profile, with low daytime values (111 pg/ml) and high nighttime concentrations (791 pg/ml). Taken together, these results evidence a high degree of plasticity for sharpsnout seabream activity patterns, as well as phasing independence of locomotor and feeding rhythms. Finally, the existence of a well-defined daily rhythm of plasma melatonin was found.

Animals↗

PubMed2006

Melatonin effects on food intake and activity rhythms in two fish species with different activity patterns: Diurnal (goldfish) and nocturnal (tench).

Melatonin has several known physiological functions, the main one being synchronization of daily and seasonal rhythms. In addition, melatonin has been reported to influence food intake and behavioral rhythms with varying results depending on the species. The aim of this research was to evaluate the effects of intraperitoneal melatonin injection on food intake and locomotor activity in two different fish species: goldfish (diurnal) and tench (nocturnal), under different light regimes: constant light (LL) conditions or LD 12:12, with melatonin administration at mid-light (ML), mid-dark (MD), and after a 1-h light pulse at MD. In addition to these acute tests, in the case of goldfish we also investigated the effects of daily melatonin administration for 1 week. Our results indicated that acute melatonin administration significantly decreased goldfish food intake (16-52% inhibition, depending on the light regime) and locomotor activity (55-100%), with the chronic treatment inducing a similar total food intake inhibition that persisted for 7 days. In tench, a nocturnal fish species, acute melatonin administration at MD and ML reduced food intake (37% and 29%, respectively), while locomotor activity was not affected at MD and slightly increased at ML. Taken together, these results indicated that melatonin reduced food intake in both species, while its effects on locomotor activity depended on the time of administration (light or dark phase) and the activity patterns of the species.

Animals↗

PubMed2006

Effects of melatonin administration on oxidative stress and daily locomotor activity patterns in goldfish.

Melatonin has a number of physiological functions in addition to light-dark transduction. In recent years, many in vivo and in vitro studies in rodents have revealed an important antioxidant activity of melatonin, both directly and indirectly. Nevertheless, the potential effects of melatonin as an antioxidant in fish remain unknown. The aim of this research was to evaluate the capacity of melatonin injections (3 mg/kg) to attenuate oxidative damage after submitting goldfish to oxidative stress caused directly by hydrogen peroxide (H2O2) baths and indirectly by hypoxia and subsequent reoxygenation, as well as the locomotor activity. The results revealed that melatonin decreased lipid damage in muscle after hypoxia/reoxygenation (1.22 vs. 2.27 nmoles lipid peroxides/g tissue), but not in liver. Mortality caused by oxidative stress was not attenuated by melatonin. Surprisingly, melatonin caused an increase of mortality (50 vs. 95%) when administered before hypoxia. Locomotor activity was also affected by melatonin but not by the administration of the vehicle, suggesting a sedative effect of melatonin in goldfish. In conclusion, melatonin administration provoked slight effects on lipid peroxidation and mortality resulting from oxidative stress, with reduction of locomotor activity in relation to the vehicle.

Animals↗

PubMed2005

Oral serotonin administration affects the quantity and the quality of macronutrients selection in European sea bass Dicentrarchus labrax L.

Teleost fish are able to regulate their energy intake selecting from pure macronutrients sources, but the regulatory mechanisms involved in macronutrients selection remain unknown. Serotonin (5-HT) reduces food intake in mammals and fish and modifies the macronutrients selection pattern in mammals; however, no information is available about its role on macronutrients selection in fish. The aim was to determine the effect of orally administered 5-HT (0.1, 0.5 and 2.5 mg kg BW(-)(1)) into gelatine capsules on the subsequent macronutrient selection of sea bass, using for this purpose gelatine capsules including carbohydrates, protein, or lipids separately. The voluntary ingested 5-HT was released into the plasma of fish, reaching a level two times greater than the controls, 45 min after the ingestion of a capsule containing 2.5 mg kg BW(-1) of 5-HT. The indoleamine, at doses of 0.1, 0.5 and 2.5 mg kg BW(-1), produced a reduction in total food intake of 31%, 49% and 37%, respectively, compared to the baseline, modifying the macronutrient selection pattern. The percentage of fat selected was significantly reduced whereas the percentage of protein significantly increased after administration of highest dose, but no changes were observed in the proportion of carbohydrate for any 5-HT doses. In conclusion, oral administration of 5-HT affected both amount of food intake and pattern of macronutrients selected. This is the first evidence supporting a role of 5-HT as a neurohumoral mediator involved in macronutrients selection in fish.

Administration, Oral↗

PubMed2005

Effects of salinity on food intake and macronutrient selection in European sea bass.

Salinity is one of the most relevant environmental parameters in regards to fish physiology, modifying food intake and growth performance in many fish species; however, its possible effects on macronutrient selection are still unknown. The aim of this study was to determine the effects of three salinity levels (25 per thousand, 7 per thousand, and 0 per thousand) on total food intake and encapsulated macronutrient selection in a euryhaline teleost, European sea bass. A total of 40 fish (five per tank) with an average body weight of 52.4 +/- 7.1 g were used. Lowering the salinity level from 25 per thousand to 7 per thousand and 0 per thousand reduced food intake by 27% and 42%, respectively. Regarding macronutrient selection, these salinity changes significantly decreased the percentage of CH intake by 31% and 27%, while increasing that of P by 30% and 25%, respectively. Fat selection remained unaltered, with an average value of 22% for all tested salinities. Specific growth rate (SGR) and feed conversion efficiency (FCE) were affected by macronutrient selection pattern, which in turn was salinity-dependent. These results indicate a strong influence of salinity on European sea bass food intake and macronutrient selection.

Analysis of Variance↗

PubMed2005

Fish macronutrient selection through post-ingestive signals: effect of selective macronutrient deprivation.

Recent reports describe teleosts as being able to regulate energy intake by selecting from pure macronutrient sources, although the regulatory mechanisms involved in this selection remain unknown. The aim of the present work was to determine the effect of selective macronutrient deprivation on energy regulation and macronutrient selection, using for this purpose carbohydrate (CH), protein (P), and fat (F) packaged separately into gelatin capsules, a method that prevents the diet chemosensory properties at oropharyngeal level from interfering with macronutrient selection. Twenty-four individually housed sea bass (Dicentrarchus labrax) were subjected to two experiments: (a) two-macronutrient deprivation, and (b) one-macronutrient deprivation. In two-macronutrient deprivation, fish were fed sequentially with P, CH, or F, and in one-macronutrient deprivation, they were fed sequentially with two separately packaged macronutrients (P and CH, CH and F, or P and F). There was a rapid reduction of macronutrient intake in two-macronutrient deprivation, reaching 80% inhibition after 4, 5, and 7 days of P, CH, and F intake, respectively. In one-macronutrient deprivation, the energy intake was significantly reduced during selective F deprivation, but not with P or CH deprivation. Although the fish were being fed with only two macronutrients, the relative proportions of these macronutrients in each selective deprivation phase were the same as the baseline. These results show that in deprivation studies fish need at least F plus one other macronutrient to regulate their energy intake, and that their macronutrient selection is stable even when one is absent. In summary, fish seem to regulate energy and macronutrient selection through post-ingestive mechanisms probably involving chemosensory detection in the gut, and/or post-absorptive mechanisms.

Animal Feed↗

PubMed2005

Demand-feeding rhythms and feeding-entrainment of locomotor activity rhythms in tench (Tinca tinca).

Tench (Tinca tinca) has been described as a strictly nocturnal species whose locomotor activity rhythms, albeit strongly synchronised by light, have an endogenous nature. Aside from light, a number of other environmental factors, such as mealtime, can act as circadian system synchronisers in fish; however, there is a scarcity of information on tench feeding rhythms. This study describes daily self-feeding rhythms in tench, and analyses the role of feeding time on synchronisation of locomotor activity rhythms. Tench were able to operate string sensor-activated self-feeders, and they displayed a strictly nocturnal behavior, both under indoor and outdoor conditions. Locomotor activity remained strictly nocturnal irrespective of whether tench were fed only during the scotophase (D-feeding) or the photophase (L-feeding). However, no statistically significant differences were detected between both groups in terms of food intake or growth performance. Furthermore, unlike L-feeding, D-feeding elicited a clear anticipatory activity (FAA). When tench were given the possibility of feeding at both times of the day, they showed a clear preference for D-feeding. Finally, in fish exposed to constant darkness (DD), feeding time acted as a true zeitgeber and FAA was observed. When animals were fasted under DD conditions, locomotor activity free-run and 6 out of 12 individuals yielded significant results in the periodogram analysis. Under DD, fish resynchronised when regular food was resumed, with some tench displaying FAA. The obtained results indicated the existence of a feeding-entrainable oscillator (FEO) in tench.

Animals↗

PubMed2005

Influence of light intensity on plasma melatonin and locomotor activity rhythms in tench.

Melatonin production by the pineal organ is influenced by light intensity, as has been described in most vertebrate species, in which melatonin is considered a synchronizer of circadian rhythms. In tench, strict nocturnal activity rhythms have been described, although the role of melatonin has not been clarified. In this study we investigated daily activity and melatonin rhythms under 12:12 light-dark (LD) conditions with two different light intensities (58.6 and 1091 microW/cm2), and the effect of I h broad spectrum white light pulses of different intensities (3.3, 5.3, 10.5, 1091.4 microW/cm2) applied at middarkness (MD) on nocturnal circulating melatonin. The results showed that plasma melatonin in tench under LD 12:12 and high light conditions displayed rhythmic variation, where values at MD (255.8 +/- 65.9 pg/ml) were higher than at midlight (ML) (70.7 +/- 31.9 pg/ml). Such a difference between MD and ML values was reduced in animals exposed to LD 12: 12 and low light intensity. The application of 1 h light pulses at MD lowered plasma melatonin to 111.6 +/- 3.2 pg/ml (in the 3.3-10.5 microW/cm2 range) and to 61.8 +/- 18.3 pg/ml (with the 1091.4 microW/cm2 light pulse) and totally suppressed nocturnal locomotor activity. These results show that melatonin rhythms persisted in tench exposed to low light intensity although the amplitude of the rhythm is affected. In addition, it was observed that light pulses applied at MD affected plasma melatonin content and locomotor activity. Such a low threshold suggests that the melatonin system is capable of transducing light even under dim conditions, which may be used by this nocturnal fish to synchronize to weak night light signals (e.g., moonlight cycles).

Animals↗

PubMed2005

How to engage medical students in chronobiology: an example on autorhythmometry.

This contribution describes a new laboratory experience that improves medical students' learning of chronobiology by introducing them to basic chronobiology concepts as well as to methods and statistical analysis tools specific for circadian rhythms. We designed an autorhythmometry laboratory session where students simultaneously played the role of researchers and experimental subjects. During this session, which lasted 24 h, students recorded their own arterial pressure, heart rate, oral temperature, forced expiratory flow, glucose tolerance, muscular strength, reaction time, and sensorimotor coordination at regular intervals and also took the Horne and Ostberg test, after which they analyzed their own data. Furthermore, to gather information from subjects under normal sleep and eating schedules, some students acquired data at home. To guide and help students with their work, a dedicated web page was implemented with scientific references, cosinor analysis software, and other valuable information. All these "raw" data were combined into a single database that students could use to evaluate whatever aspect of the data they seemed fit. A number of suggestions were offered to them as guidance. Students were then instructed to write a scientific article on the subject they had chosen. The experience was highly rewarding for both instructors and students alike. In view of the high level of absenteeism in Spanish universities and the fact that 93% of the students attended the exam and 95% of these passed, the experience was considered a great success.

Adult↗

PubMed2004

Binding characteristics and daily rhythms of melatonin receptors are distinct in the retina and the brain areas of the European sea bass retina (Dicentrarchus labrax).

Melatonin is synthesized, with a circadian rhythm, in the pineal organ of vertebrates, high levels being produced during the scotophase and low levels during the photophase. The retina also produces melatonin, although in the case of the European sea bass, its secretion pattern appears to be inverted. In the study described here, radioreceptor assay techniques were used to characterize the melatonin binding sites, their regional distribution and their daily variations. Brain and retina membrane preparations were used in all the binding assays and 2-[125I]iodomelatonin ([125I]Mel) as radioligand at 25 degrees C. The specific binding of [125I]Mel was seen to be saturable, reversible, specific and of high affinity. In all the tissues assayed, the power of the ligands to inhibit [125I]Mel binding decreased in the following order: melatonin>>4-P-PDOT>luzindole> or =N-acetylserotonin, which points to the presence of Mel1-like receptors. The inhibition curves of 4-P-PDOT suggested the presence of two different binding sites in the brain areas, but only one type of site of low affinity in the neural retina. No daily variations in [125I]Mel binding capacity (Bmax) or affinity (Kd) were detected in the brain areas, while a clear rhythm in Kd melatonin receptor affinity and Bmax binding capacity was observed in the retina. Kd and Bmax retinal rhythms were out of phase with the lowest Kd and the highest Bmax occurring at scotophase. This result suggests that retinal melatonin is a paracrine factor able to control receptor desensitization during photophase when ocular melatonin is higher in this species.

Animals↗

PubMed2004

Daily locomotor activity and melatonin rhythms in Senegal sole (Solea senegalensis).

The daily locomotor and melatonin rhythms of the Senegal sole, a benthonic species of increasing interest in aquaculture, are still unknown, despite the fact that such knowledge is of prime importance for optimising its production. The aim of the present research was therefore to investigate the daily rhythms of locomotor activity and melatonin in the Senegal sole. For this purpose, the individual locomotor activity rhythms of fish were registered using a photocell. Plasma and ocular melatonin rhythms were studied in animals reared in circular tanks placed in earth under an LD 12:12 light regime and 16-18 degrees C temperature range (spring equinox). Blood and eye samples were taken every 3 h during a complete 24-h cycle. The impact of a light pulse in the middle of the dark period (MD) on plasma melatonin was also studied. Locomotor activity was mainly nocturnal, with 84.3% of the total activity occurring during darkness. The levels of plasma melatonin were higher at night (55 pg/ml) than during the day (2 pg/ml), while ocular melatonin levels appeared to be arrhythmic. Both weight and melatonin content were found to be significantly higher in the left eye in relation to the right eye. A light pulse in MD provoked a significant decrease in plasma melatonin levels. In summary, photoperiod is a key factor in synchronizing locomotor activity and melatonin rhythms in the Senegal sole, whose nocturnal habits should be taken into account for their rearing by aquaculture.

Animals↗

PubMed2004

Effect of photoperiod manipulation on the daily rhythms of melatonin and reproductive hormones in caged European sea bass (Dicentrarchus labrax).

Reproduction in fish is cyclical and timed to guarantee the survival of the offspring. Seasonal variations in reproductive hormones of fish have been deeply investigated in fish over the last years. However, there are few studies regarding the daily changes in reproductive hormone profiles in teleosts. The aim of the present research was to investigate the effects of photoperiod manipulation on melatonin and reproductive hormones (pituitary sbGnRH, pituitary LH and plasma LH, testosterone [T], and 11-ketotestosterone [11KT]) daily rhythms in male sea bass, kept in net cages under farming conditions in winter (9L:15D). Fish were distributed in two groups, one under constant long photoperiod (18L:6D) and the other under natural photoperiod. The photoperiod strongly influenced the daily melatonin profile, so that the duration of the nocturnal melatonin rise was longer in the control group than in the group exposed to the artificial photoperiod (18L:6D). A daily rhythm was observed in the pituitary sbGnRH profile in both groups, showing the lowest levels during the dark period. A daily rhythm of pituitary LH was detected in the control group, which was suppressed in the group under long photoperiod. Daily variations in plasma LH were observed, the highest levels being found in the dark phase in both groups, although this profile was significantly altered by artificial light, maintaining a fixed relationship between the first nocturnal rise of melatonin and the nocturnal peaks of plasma LH in both groups. Plasma T levels showed significant fluctuations in their daily cycle following a sinusoidal pattern with an acrophase around sunrise in both groups, without any influence of light regime. No significant daily variations in plasma levels of 11-KT were observed in none of the groups. Our results provide the first evidence of the presence of daily variations in pituitary sbGnRH content, pituitary and plasma LH, and plasma T in sea bass. Artificial lights suppressed the circulating melatonin and significantly affected the daily rhythm of LH storage and release.

Animals↗

PubMed2004

Oral administration of melatonin reduces food intake and modifies macronutrient selection in European sea bass (Dicentrarchus labrax, L.).

Seasonal and circadian changes have been observed in dietary selection and feeding behavior of fish. It is known that the light-dark cycle is the principal mediator of the production of pineal-derived melatonin in fish, and also that the digestive tract synthesizes and secretes melatonin and indeed is the principal extrapineal source of this secretor product, suggesting that melatonin could be involved in the processes of feeding and/or digestion. Fish are capable of regulating their energy intake from separate sources of macronutrients, but the mechanisms of this selection process are unknown. In the present paper, we explored the effect of melatonin administered orally to European sea bass on their selection of encapsulated macronutrients. Melatonin doses of 0.1, 0.5, and 2.5 mg/kg body weight were administered in gelatin capsules. The voluntarily ingested melatonin was absorbed into the fish's plasma, 45 min after the administration reaching a level depending on the dose that was up to 26 times greater than the controls with the highest dose of melatonin. The indole produced a dose-dependent inhibition of total food intake of 9, 26, and 34%, respectively, and also modified the pattern of macronutrient selection. Carbohydrate intake was significantly reduced (by 17, 33, and 42% for the three doses, respectively), but the observed reductions in fat and protein intake were not statistically significant. On the contrary, fat percentage significantly increased for the highest dose, but no changes were observed in the protein or carbohydrate percentages for any of the melatonin doses. In conclusion, orally administered melatonin affected both the amount of food consumed and the pattern of macronutrients selected. This is the first evidence for the existence of neurohumoral mediators involved in the selection of macronutrients in fish.

Administration, Oral↗

PubMed2003

Macronutrient selection through postingestive signals in sea bass fed on gelatine capsules.

The role of the food orosensory properties on protein (P), fat (F) and carbohydrate (CH) self-selection was investigated in fish fed gelatine capsules containing pure macronutrients. A total of 40 sea bass (39.6+/-6.2 g initial body weight) distributed in eight 75-l tanks were used. In a sequence of experimental phases, sea bass were fed a pelleted complete diet, an encapsulated complete diet or a combination of separately encapsulated pure macronutrients. In order to induce associative learning, capsules containing a given macronutrient were paired with a particular colour. Our results demonstrate that fish are able to regulate food intake, so as to balance their energy intake, when they are fed a complete encapsulated diet and, therefore, without using the orosensory properties of the diet. Moreover, sea bass learn to discriminate and select among colour-coded, pure macronutrient capsules to compose a complete and balanced diet using colour as the only external cue. The composition of selected diet was 55% P, 23% CH and 22% F in terms of macronutrient percentage. The diet orosensory properties do not seem to be necessary to regulate macronutrient intake either, suggesting that an associative learning between capsule colour and content can be established through monitoring of macronutrient intake by postingestive and/or postabsorptive mechanisms. These results provide the first insight into energy and macronutrient self-selection by fish fed on gelatine capsules containing separate macronutrients.

Animals↗