Thierry Boujard

Food intake in fish.

List of Contributors. Preface. Feed Composition and Analysis (Malcolm Jobling). Feed Types, Manufacture and Ingredients (Malcolm Jobling, Emidio Gomes and Jorges Dias). Techniques for Measuring Feed Intake (Malcolm Jobling, Denis Coves, Borge Damsgard, Henrik R. Kristiansen, Juha Koskela, Thuridur E. Petursdottir, Sunil Kadri and Olafur Gudmundsson). Experimental Design in Feeding Experiments (Kari Ruohonen, Juhani Kettunen and Jonathan King). Gustation and Feeding Behaviour (Charles F. Lamb). Environmental Factors and Feed Intake: Mechanisms and Interactions (Patrick Kestemont and Etienne Baras). Environmental Factors and Feed Intake: Rearing Systems (Marie--Laure Begout Anras, Marilyn Beauchaud, Jon--Erik Juell, Deniks Coves and Jean--Paul Lagardere). Feeding Rhythms (Juan Antonio Madrid, Thierry Boujard and F. Javier Sanchez--Vazquez). Feeding Anticipatory Activity (F. Javier Sanchez--Vazquez and Juan Antonio Madrid). Effects of Feeding Time on Feed Intake and Growth (Valerie Bolliet, Mezian Azzaydi and Thierry Boujard). Effects of Nutritional Factors and Feed Characteristics on Feed Intake (Manuel de la Higuera). Regulation of Food Intake by Neuropeptides and Hormones (Nuria de Pedro and Bjorn Thrandur Bjornsson). Physiological Effects of Feeding (Chris Carter, Dominic Houlihan, Anders Kiessling, Francoise Medale and Malcolm Jobling). Feeding Management (Anders Alanara, Sunil Kadri and Mihalis Paspatis). Nutrient Partitioning and the Influence of Feed Composition on Body Composition (Malcolm Jobling). Glossary of Terms. Index

Digestibility of extruded peas, extruded lupin, and rapeseed meal in rainbow trout (Oncorhynchus mykiss) and turbot (Psetta maxima)

Apparent digestibility coefficients (ADC) of nutrients and energy of extruded peas, extruded lupin and rapeseed meals were determined in juvenile rainbow trout and turbot. Extruded lupin was found to be a promising substitute for fish meal in the diets of trout and turbot, with an acceptable digestibility of its dry matter (70% in trout and 81% in turbot) and a high digestibility of its protein (96% in trout and 98% in turbot) and its energy (77% in trout and 85% in turbot). Extruded peas had a lower digestibility of its protein in trout (88%) than in turbot (92%), and the ADC of energy, mainly supplied as starch, was relatively low (69% in trout and 78% in turbot). The digestibility of rapeseed meal was improved by a thermal treatment. Without thermal treatment, rapeseed meal had a low digestibility of its dry matter (57%) and energy (69%) in turbot. The availability of phosphorus was higher for extruded lupin (62% in trout and 100% in turbot) compared to the other plant-ingredients. When compared to a solvent-extracted meal, the availability of phosphorus from rapeseed meal was improved by heat treatment in both species (42% vs. 26% in trout and 65% vs. 49% in turbot).

Potential of plant-protein sources as fish meal substitutes in diets for turbot (Psetta maxima): growth, nutrient utilisation and thyroid status.

Abstract An experiment was conducted in order to assess the incorporation in diets for juvenile turbot of extruded lupin ( Lupinus albus ) and heat-treated (RM1) or untreated (RM2) rapeseed meals ( Brassica napus ) (26 and 40 μmol glucosinolate/g DM, respectively). The level of incorporation of 30% for each plant-protein, as well as 46% for RM1 and 50% for lupin was tested and compared with a fish meal based control diet. Triplicate groups of turbot (initial body weight of 66 g) were fed by hand with isonitrogenous and isoenergetic experimental diets, twice daily and to visual satiety, during 63 days. Extruded lupin can be incorporated in diets of turbot up to a level of 50% without adverse effects on growth performance and body composition. Rapeseed meal can only be incorporated at levels up to 30%, but a preliminary heat treatment of RM is necessary in order to improve its nutritional quality. In turbot-fed the RM-based diets, plasma T 4 levels were reduced with low dietary content in glucosinolate breakdown products (3.6 μmol/g), but no decrease in plasma T 3 levels was observed with the higher level of toxic compounds (4.4 μmol/g). A significant deiodinase type II compensatory effect, leading to an increase of the conversion of T 4 to T 3 , was observed in vitro in the liver of turbot fed RM1-based diets. The intake of lupin-based diets also had an effect on thyroid status with an increase of plasma T 3 levels and of deiodinase type I activity in liver and kidney, suggesting an increase in the degradation of rT 3 and in the conversion of T 4 to T 3 .

Voluntary feed intake, nitrogen and phosphorus losses in rainbow trout (Oncorhynchus mykiss) fed increasing dietary levels of soy protein concentrate

High energy extruded diets were formulated to contain the same level of protein supplied either by soy protein concentrate (SPC) or fish meal. Three experiments were performed in order to measure voluntary feed intake and feed waste, faecal losses and soluble losses of nitrogen and phosphorus in rainbow trout (average body weight: 100 g). Voluntary feed intake and growth performance of fish fed with demand feeders were not different when diets contained 0, 50 or 75 % SPC instead of fish meal. Total replacement of fish meal by SPC led to a significant decrease in feed intake and resulted in poor growth. This was partly due to methionine deficiency in the SPC based diet. With the addition of crystalline DL-methionine in the diets, an improvement of feed intake and growth performance was apparent. Protein digestibility was high, regardless of the protein source. Excretion of ammonia and urea increased with the level of SPC in the diet. Nitrogen losses decreased when methionine was added to the diet containing only SPC as a protein source. Availability of phosphorus increased with the level of SPC in the diets. Daily soluble losses were not affected by the dietary treatments but the pattern of phosphorus excretion after feed intake was modified. The rise in soluble phosphorus in water occurred later when fish were fed diets with soy protein whatever the dietary level of soy protein concentrate.

Diel feeding activity and the effect of time-restricted self-feeding on growth and feed conversion in European sea bass

The feeding rhythm and growth performance of European sea bass Dicentrarchus kzbrar (initial weight 65 g) were studied under free and time-restricted access to self-feeders. Under free access to the feeders, significant feeding rhythms with a nocturnal acrophase were observed, although there was considerable variability between replicates. When access to the self-feeders was restricted to two periods of 4 h day-‘, the feed demand (FD) was reduced at the beginning of the experiment but not at the end, indicating that the period of adaptation, rather than appetite, was affected by such feeding practice. When access to the self-feeders was restricted to only one period of 4 h day- I, two thirds of the replicates eventually displayed FD similar to the fish having free access to feed, indicating that the restricted temporal access to feed could be compensated for. There was no detectable effect of feeding protocol on feed conversion or body composition, but growth was closely related to the total FD. Thus, growth was influenced by the fact that fish subjected to a time-restricted access to feed needed time to adapt to the new feeding situation. The results indicate that sea bass are capable of operating self-feeders, and can easily modify their feeding, resulting in both good growth performance and good feed conversion. Kqvwords: Sea bass; Self-feeding; Growth; Feed conversion

Incorporation of high levels of extruded lupin in diets for rainbow trout (Oncorhynchus mykiss): nutritional value and effect on thyroid status

Three experiments and a digestibility trial were conducted in order to assess the incorporation of extruded lupin (Lupinus albus) in diets for juvenile rainbow trout. Digestibility of protein and phosphorus were higher in lupin than in fish meal, but digestibility of dry matter and energy were lower. The first trial was designed to determine the maximum level of incorporation of lupin in the diet of trout. Levels of 30, 50 and 70% were tested and compared with a fish meal-based control diet. The diets were formulated to be isonitrogenous and isoenergetic. Triplicate groups of trout were fed twice daily to visual satiety by hand during 64 days. Two subsequent trials, using another yearly crop of lupin, were performed to analyze the effects of very high levels of incorporation of lupin. Growth performances, feed intake and nitrogen balance of fish fed diets with 50% of lupin incorporation were comparable to those of fish fed the control diet. However, higher fat deposition was observed. Incorporation of lupin led to higher phosphorus retention and lower phosphorus excretion, but only in two of the three trials. In trout fed the diets containing 70% lupin, growth was reduced by 41%, feed intake by 15% and nitrogen retention by 12% when the first crop of lupin was used. Feed intake was not reduced and growth performance was higher when the second crop of lupin was used, i.e., a decrease of only 16% when fish were fed by hand to satiety (decrease of feed efficiency) or null when fish were fed on demand using self-feeders. The incorporation of lupin can lead to a decrease in plasma thyroxine levels, but this effect was not clear and not recurring. However, when this effect was observed, a deiodinase compensatory effect adjusted the plasma triiodothyronine levels. In general, the plasma triiodothyronine levels were related to the growth performance of the trout.

A comparative study of automatic feeding and self-feeding in juvenile Atlantic salmon (Salmo salar) fed diets of different energy levels

Abstract The growth performances of juvenile Atlantic salmon fed diets differing in energy content, either using self-feeders or in excess with automatic feeders, were compared. In addition, the pattern of feeding activity is described for fish fed with self-feeders. In fish fed using self-feeders, growth was intermediate between the performance of fish fed with low and high energy diets by means of automatic feeders. Fish groups tended to become more homogeneous in size with the passage of time, this being more pronounced in groups fed using self-feeders than in those fed using automatic feeders. Dietary energy content influenced growth and digestible energy intake of salmon fed by means of automatic feeders, but this was not seen in self-fed salmon. These results indicate that regulation of feed intake is influenced by the feeding strategy, probably because pellets are only available on demand for fish fed with self-feeders, whereas in groups fed by means of automatic feeders, pellets are freely available in excess. In fish fed with self-feeders, all feed distributed appeared to have been eaten. Feeding activity showed a main peak during the first hours of light and a second, smaller, peak at the end of the light phase. It is concluded that Atlantic salmon feeds preferentially during the photophase and can be fed efficiently with self-feeders.

Influence of oligosaccharides on the digestibility of lupin meals when fed to rainbow trout, Oncorhynchus mykiss

We examined the influence of the oligosaccharide component of a lupin (Lupinus angustifolius) meal when fed to rainbow trout. Two strategies for examining the influence of oligosaccharides were undertaken, including the use of an exogenous enzyme supplement of α-galactosidase to degrade the oligosaccharides and ethanol extraction processing to remove the oligosaccharides. Controls for both processing and degradation of the galactosides were also included in the study. The test treatments were fed to the fish as 30% of their diet and were compared against a reference diet using standard diet-dilution digestibility techniques. The removal of the ethanol-soluble component of the lupin meal had the greatest influence on its apparent digestibility, with significant effects clearly seen on the digestibility of the nitrogen, organic matter and nitrogen-free extractive (NFE) components. Addition of exogenous α-galactosidase to the lupin meal produced a significant difference in the digestibility of nitrogen and numerical improvements in the values of most nutrient parameters. Comparison of the digestibilities of the enzyme-supplemented lupin meal, the galactose-supplemented extracted lupin meal and the original lupin meal treatments indicated that rainbow trout can absorb the monosaccharides produced from the degradation of α-galactosides. This improvement was further validated by examining the influence of the ethanol extraction process, which showed that it is the removal of the ethanol-soluble components, most likely oligosaccharides, that is the contributing factor. These findings indicate that further processing of lupin meals to remove their oligosaccharide fraction would have beneficial nutritional implications for fish.

Demand-feeding rhythm in rainbow trout and European catfish : synchronisation by photoperiod and food availability

The effect of light-dark (LD) cycle and food availability was tested on the demand-feeding rhythm of single and groups of rainbow trout and European catfish. Under LD and free food access, most trout and catfish displayed, respectively, a diurnal and a nocturnal pattern of demand-feeding activity, whereas a few fish or groups of fish switched from diurnalism to nocturnalism or vice versa. In both species held under constant lighting conditions and a restricted feeding (RF) cycle (RF 20:4), the demand-feeding rhythm rapidly synchronised to food availability. The demand-feeding rhythm was under endogenous control and, in rainbow trout, periodogram analysis suggested the existence of two oscillators, one synchronised by photoperiod (LEO) and the other by food (FEO). When submitted to both LD and RF cycles, LD was, at least in the rainbow trout, the dominant zeitgeber synchronising the demand-feeding rhythm. In catfish, food availability rapidly synchronised demand-feeding rhythm. Finally, in both species, the synchronisation of single fish to LD or feed availability appeared slower than that of groups of fish, supporting the idea that social organisation affects the circadian activity in fish.

Dietary low-glucosinolate rapeseed meal affects thyroid status and nutrient utilization in rainbow trout (Oncorhynchus mykiss).

Two rapeseed (Brassica napus) meals, RM1 and RM2, with two levels of glucosinolates (GLS; 5 and 41 mumol/g DM respectively) were incorporated at the levels of 300 and 500 g/kg of the diets of juvenile rainbow trout (Oncorhynchus mykiss) in replacement of fish meal, and compared with a fish-meal-based diet. A decrease in the digestibility of the DM, protein, gross energy and P was observed with high-rapeseed meal (RM) incorporation. In trout fed on RM-based diets, growth performance was reduced even after only 3 weeks of feeding. Feed efficiency was adversely affected by RM and GLS intake. Protein and energy retention coefficients were significantly lower in fish fed on the diet containing the higher level of GLS. P retention was significantly lower with all the RM-based diets than with the fish-meal diet. Irrespective of the degree of growth inhibition, fish fed on RM-based diets exhibited similar typical features of hypothyroid condition due to GLS intake, expressed by lower plasma levels of triiodothyronine and especially thyroxine and a hyperactivity of the thyroid follicles. This hypothyroidal condition led to a strong adjustment of the deiodinase activities in the liver, the kidney and the brain. A significant increase of the outer ring deiodinase activities (deiodinases type I and II respectively) and a decrease of the inner ring deiodinase activity (deiodinase type III) were observed. It is concluded that the observed growth depression could be attributed to the concomitant presence of GLS, depressing the thyroid function, and of other antinutritional factors affecting digestibility and the metabolic utilization of dietary nutrients and energy.