Gastric emptying and the return of appetite in juvenile turbot, Scophthalmus maximus L., fed on artificial diets

Abstract

Gastric emptying time in Scophthalmus maximus, when fed friable artificial pellets based on fishmeal. is composed of two phases: (a) a delay time ( I d ) during which the meal forms a bolus and which shortens with temperature, and (b) an emptying phase (duration tend) which varies with meal size (8, body weight ( W ) and temperature (0 according to: log, tcnd=4.66+0.448 log, S-0.2664 log, W-0.051 7 (where tend is in h, S is in g, W is in g and Tis C). During the emptying phase, stomach contents decrease curvilinearly according to: S,O.448 = S00.448 -0.448 K (where S, & So is in g and I is in h) in which the instantaneous digestion rate, K , varies with fish weight and temperature as: ~= 0 . 0 2 1 ~0 . 2 6 6 4 p 5 1 iFood pellets were prepared which remained separate and did not form a bolus in the stomach; K increased if a given meal size was subdivided to increase surface area. If meal size was increased by ingestion of identical pellets, K decreased. After a satiation meal, appetite in young turbot returns in direct relation to the degree of stomach emptiness. When food is regularly available, young turbot feed steadily at a rate which maintains their stomachs at c. 85% maximum fullness.When trained to use demand feeders, the fish interact a s a group to feed rhythmically. but feeding rate falls 33% to only two-thirds of the previous rate since stomach fullness, and hence digestion rate (g h-I). i s maintained at a lower level. Reduction in dietary energy density below I kCal g -' increases gastric emptying rate and the turbot demonstrate partial compensation by increasing food intake. On energy-rich diets, protein nitrogen and energy assimilation efficiencies remain high (97.5% and 91 YO respectively) irrespective of feeding rate and frequency.

Effects of meal and body sizes on gastric evacuation rate in brooktrout Salvelinus fontinalis (Mitchill, 1814) fed commercial pellets in group feeding

“…Diet with higher energy has been found to depress the GE rate of fish (Jobling, 1987). Similar to length exponent, a lower value of mass exponent was also reported by Grove et al (1985) for turbot fed pellet feed.…”

“…The general applicability of the square root model properly describes the evacuation of different fish and crustacean prey from the stomachs of whiting Merlangius merlangus, saithe Pollachius virens and cod Gadus morhua, fed different meal sizes (Andersen, 2001). The square root model has been used to describe the pattern of evacuation in various other fish species such as pikeperch Stizostedion lucioperca (Koed, 2001) and coho salmon Oncorhynchus kisutch (Andersen and Beyer, 2007); different gadoids (Jones, 1974;Temming and Herrmann, 2003) and turbot Scophthalmus maximus (Grove et al, 1985).…”

Gastrointestinal and metabolic effects of feeding schedule on voluntary feed intake and growth of European eel, Anguilla anguilla

“…Feed intake is also expressed as daily average, i.e., for the fish fed once every 2 days feed intake (meal size) on alternate days was twice the average (cf. are the most important determinants (Grove et al 1978(Grove et al , 1985Seymour 1984;Hossain et al 1998;Tekinay et al 2003;Riche et al 2004). Stomach capacity has been estimated more or less directly by filling dissected stomachs with fluid and measuring the volume at a fixed pressure (Jobling et al 1977;Ruohonen and Grove 1996;Grove et al 2001), or indirectly by equating stomach capacity with maximal meal size either as maximum amount eaten per meal or as maximal stomach content after a satiation meal (Hossain et al 1998;Riche et al 2004;Tekinay et al 2003).…”

“…Shortterm feed intake is, therefore, often expressed as the closely related concept appetite, defined as the instantaneous willingness to eat, which is often measured as the amount of feed consumed per meal, or per opportunity to eat (Langhans 1999). With fish, much attention has been given to the return of appetite with time after a satiation meal (Grove et al 1978(Grove et al , 1985Seymour 1984;Hossain et al 1998;Tekinay et al 2003;Riche et al 2004). During a meal an animal becomes satiated, when internal signals provide a negative feedback, which at a certain treshold will tell the animal to stop eating (Langhans 1999).…”

“…The feeding schedule has been shown to affect growth of fish through an effect on average group feed intake (Seymour 1984; Van der Meer et al 1997;Ruohonen et al 1998;Riche et al 2004) but also on variation in intake and growth between individuals within a group (Jobling 1983;Petursdottir 2002;Almazan-Rueda et al 2004). Effects on feed intake are mainly linked to gastrointestinal factors, stomach fullness and stomach emptying after a single satiation meal, often combined with measured or calculated implications towards optimal feeding schedules (Grove et al 1978;1985;Bromley 1987;Hossain et al 1998) The present study intended to optimise the feeding schedule for European eel, Anguilla anguilla L., by examining the effect of feeding schedule on group and individual feed intake and growth and by investigating if variation in feed intake and growth with feeding schedule could be related to variation in gastrointestinal and metabolic factors.…”