Anders Kiessling

Changes in the structure and function of the epaxial muscle of rainbow trout (Oncorhynchus mykiss) in relation to ration and age: I. Growth dynamics

Abstract Growth of white and red muscle fibres was studied in a feeding ration experiment with rainbow trout, from hatching until sexual maturity (2.5 years). The trout were fed ration levels (RL) which ranged from appreciable underfeeding to overfeeding (RL=25% and 200% of full ration, respectively). They were also subjected to changed rations in order to study adaptation effects and recovery growth. The ratio of carcass to body weight (CW%) indicated that in young fish (0.3 year) on a restricted ration, growth of internal organs was favoured compared with that of total muscle. In older fish all groups, irrespective of ration, increased their carcass to body ratio until saltwater adaptation (1.0 year) and thereafter a sharp decline was noted. No decrease was seen in fish remaining in freshwater. There was a high correlation between body length and the length ( r 2 =0.99), width ( r 2 =0.97) and height ( r 2 =0.96) of the muscle, and also of the diameter ( r 2 =0.86-0.93) and length ( r 2 =0.94) of individual white muscle fibres. In fish with a body length less than 250 mm, red fibre diameter was more closely related to ration level than to body length and vice versa in larger fish. In large fish, recruitment of small fibres was seen in all muscles studied. However, periods of rapid growth favoured fibre hypertrophy and periods of slow growth fibre recruitment. Significant differences were found between the lateral and the dorsal parts of the white epaxial muscle, suggesting different growth rates in the two muscle areas.

Anaesthesia of farmed fish: implications for welfare

During their life cycle as farmed animals, there are several situations in which fish are subjected to handling and confinement. Netting, weighing, sorting, vaccination, transport and, at the end, slaughter are frequent events under farming conditions. As research subjects, fish may also undergo surgical procedures that range from tagging, sampling and small incisions to invasive procedures. In these situations, treatment with anaesthetic agents may be necessary in order to ensure the welfare of the fish. The main objective of this paper is to review our knowledge of the effects of anaesthetic agents in farmed fish and their possible implications for welfare. As wide variations in response to anaesthesia have been observed both between and within species, special attention has been paid to the importance of secondary factors such as body weight, water temperature and acute stress. In this review, we have limited ourselves to the anaesthetic agents such as benzocaine, metacaine (MS-222), metomidate hydrochloride, isoeugenol, 2-phenoxyethanol and quinaldine. Anaesthetic protocols of fish usually refer to one single agent, whereas protocols of human and veterinary medicine cover combinations of several drugs, each contributing to the effects needed in the anaesthesia. As stress prior to anaesthesia may result in abnormal reactions, pre-anaesthetic sedation is regularly used in order to reduce or avoid stress and is an integral part of the veterinary protocols of higher vertebrates. Furthermore, the anaesthetic agents that are used in order to obtain general anaesthesia are combined with analgesic agents that target nociception. The increased use of such combinations in fish is therefore included as a special section. Anaesthetic agents are widely used to avoid stress during various farming procedures. While several studies report that anaesthetics are effective in reducing the stress associated with confinement and handling, there are indications that anaesthesia may in itself induce a stress response, measured by elevated levels of cortisol. MS-222 has been reported to elicit high cortisol release rates immediately following exposure, while benzocaine causes a bimodal response. Metomidate has an inhibitory effect on cortisol in fish and seems to induce the lowest release of cortisol of the agents reported in the literature. Compared to what is observed following severe stressors such as handling and confinement, the amount of cortisol released in response to anaesthesia appears to be low but may represent an extra load under otherwise stressful circumstances. Furthermore, anaesthetics may cause secondary adverse reactions such as acidosis and osmotic stress due to respiratory arrest and insufficient exchange of gas and ions between the blood and the water. All in all, anaesthetics may reduce stress and thereby improve welfare but can also have unwanted side effects that reduce the welfare of the fish and should therefore always be used with caution. Finally, on the basis of the data reported in the literature and our own experience, we recommend that anaesthetic protocols should always be tested on a few fish under prevailing conditions in order to ensure an adequate depth of anaesthesia. This recommendation applies whether a single agent or a combination of agents is used, although it appears that protocols comprising combinations of agents provide wider safety margins. The analgesic effects of currently used agents, in spite of their proven local effects, are currently being debated as the agents are administrated to fish via inhalation rather than locally at the target site. We therefore recommend that all protocols of procedures requiring general anaesthesia should be complemented by administration of agents with analgesic effect at the site of tissue trauma.

Changes in fatty acid composition in muscle and adipose tissue of farmed rainbow trout (Oncorhynchus mykiss) in relation to ration and age

To evaluate the importance of age and feed ration level (RL) on the composition of tissue fatty acid (FA) in rainbow trout (Oncorhynchus mykiss), fish were fed rations ranging from appreciable underfeeding to gross overfeeding in a longitudinal experiment lasting from start of feeding to onset of sexual maturation 2.4 years later. In order to study the effects of compensatory growth and reduced feed availability, fish were moved from high to low ration and vice versa. Changes of individual FA of total lipid (TL), triacylglycerols (TAG) and total phospholipids (PL) were studied in white and red muscle, as well as in three major adipose tissues. The effect of saltwater transfer on FA composition was also examined. A strong interdependence was found between the relative proportion of PL and TAG with changes in TL content. This was most prominent in white muscle. In parallel with this change in relative lipid class composition, a major effect was seen on FA in the TL fraction. The most marked effect of RL was an inverse relationship between 22:6 n-3 of the PUFA n-3 series and 16:1 and 18:1 of the MUFA series. This was seen in all tissues studied. It is suggested that the most important factor governing FA composition in muscle, pending changes in feed intake, is the TL content, affecting the relative level of PL and TAG. In adipose tissue, consisting mainly of TAG, more subtle changes were observed. The FA compositions of PL and TAG were not affected to any major extent by RL, except at extreme reductions. Significant changes in FA of PL and TAG were observed as an effect of saltwater transfer.

Changes in the structure and function of the epaxial muscle of rainbow trout (Oncorhynchus mykiss) in relation to ration and age. III, Chemical composition

Abstract The chemical composition of white and red muscle has been studied in rainbow trout in relation to age and ration level (RL), together with the deposition and mobilization of fat from the three main adipose tissues (viscera, dorsal and abdominal wall). Protein in red and white muscle increased with age up to 1.4 years and remained practically constant from then on, irrespective of ration level. In all tissues studied, fat content increased with age until a final steady level was reached, dependent on ration level and tissue. In white muscle and viscera, however, this increase was preceded by a decrease in fat content (0.3–1.1 years). Subjecting fish to a new RL resulted in a change in the fat content to the same level as that in fish fed at this RL from the start. The total amount of fat was regulated in all tissues, except visceral adipose tissue, by altering the relative fat content rather than by increasing or decreasing the relative size of the tissue. Overall changes in dry matter content, from hatching to sexual maturation, correlated mainly with protein in white and with fat in red muscle. However, when young and older fish were studied separately it became apparent that a change in protein content was closely related to changes in dry matter in both muscle types early in life (fish 1.1 years). The glycogen level varied in parallel in red and white muscle, except for the large increase in white versus red muscle after the glycogen depletion in connection with saltwater transfer. Subjecting fish to a new RL caused rapid changes in glycogen content in young specimens. Underfed fish produced markedly elevated levels of muscle glycogen. Season, sex or sexual maturation had no effect on the chemical composition of the muscle.

Postprandial changes in plasma free amino acid levels obtained simultaneously from the hepatic portal vein and the dorsal aorta in rainbow trout (Oncorhynchus mykiss).

SUMMARY For the first time, changes in plasma concentrations of free amino acid (AA) and their metabolites were followed simultaneously in pre- and post-hepatic blood following a single meal in non-anaesthetized and free-swimming fish. Rainbow trout (Oncorhynchus mykiss), kept in 10°C water and fitted with cannulae in the hepatic portal vein (HPV) and the dorsal aorta (DA), were force-fed 1% of their body mass and blood samples were taken from both cannulae at 0, 3, 6, 12, 24 and 48 h postprandially to follow the free AA profile. Almost all free AAs increased rapidly within the first 3 h and only a few free AAs did not change significantly over time. By 6 h, the total free AA concentration had peaked in blood taken from both the DA (7107±369 nmol ml-1) and HPV (9999±572 nmol ml-1). However, individual free AAs showed three main profiles beyond this time: for type I, a peak concentration occurred only at 6 h; for type II, there was a more gradual rise in concentration to a peak at 24 h; and for type III there were two peaks, at 6 h and 24 h. All free AAs returned to or were lower than baseline levels within 48 h, with the exception of threonine and proline. The total free AA concentrations were consistently higher (P<0.05) in the HPV than in the DA at 3 h, 6 h, 12 h and 24 h. Our data provide clear evidence that, during the first pass through the liver, hepatic modification altered individual free AA concentrations as indicated by variable ratios among the simultaneous blood samples. Furthermore, the elevation of ammonium and urea in the HPV indicates intestinal catabolism of ingested free AA before release into the HPV. In conclusion, the dual HPV and DA cannulation shows promise as a useful technique for qualitative and quantitative investigations of absorption and turnover of nutrients, especially if the measurements can be combined with reliable estimates of blood flow and labelled substances.

Comparison of fatty acid composition and astaxanthin content in healthy and by M74 affected salmon eggs from three Swedish river stocks

M74 is an extremely lethal syndrome appearing during the yolk sac-swim up stage. The syndrome is known in the Baltic Sea salmon but is still unknown in Atlantic salmon. In this study, Baltic salmon eggs from females showing M74 syndrome were compared with those from healthy females. Further, the study also included a comparison between eggs from a western (Atlantic) and two eastern (Baltic) Swedish stocks. We found differences between the Atlantic and Baltic stocks in the content of 22:6 (n-3) both in the phospholipid and triacylglycerol lipid fractions (P<0.013, P<0.0001, respectively). In addition, the eggs from the Baltic stocks had a much lower astaxanthin content than the west coast stock (P<0.0001). In the phospholipid fraction, an inverse relation was found between river temperature and 22:6 (n-3) content, when rivers were arranged according to day degrees during egg development. M74 affected eggs had a higher content of 22:6 (n-3) compared to non-affected M74 ones. We found differences in the (n-3)/(n-6) ratio between healthy and M74 eggs (P<0.0046). Also, the astaxanthin content was significantly lower in M74 eggs (P<0.0018). We suggest that egg lipid composition is under strong genetic influence. Further, we suggest that in healthy eggs of Baltic salmon, there is a balance between oxidative potential and antioxidant capacity and that a disturbance of this balance at the cellular level could possibly be a cause of the M74 syndrome.

Nutritive value of two bacterial strains of single-cell protein for rainbow trout (Oncorhynchus mykiss)

Abstract The aim of the present study was to evaluate whether two dried and autoclaved single-cell bacterial protein sources (SCP) derived from Brevibacterium lactofermentum (PL) and Bacterium glutamaticum (PR) could partially replace fish meal on an available protein basis in diets for adult rainbow trout. In two experiments, 0, 4, 8 or 16% of the diet consisted of each source of bacterial protein by replacement of fish meal. The dietary level of PL (4–16%) did not significantly influence specific growth rate, feed efficiency, carcass yield, hepatosomatic index and gonadosomatic index. Similarly, 4% PR in the diet did not influence any of the foregoing performance parameters. However, higher dietary levels of PR caused a marked reduction in growth rate and feed efficiency. Since the fish on all diets ingested roughly the same amount of feed containing PL and PR, it is possible that PR was less digestible than PL and/or that PR had a toxic/antinutritional effect on the fish. There were no differences in either amino acid or fatty acid composition of the diets. Our results suggest that PL may comprise ≥ 16% of the diet for rainbow trout by replacement of fish meal whereas caution should be exercised in the use of PR until further investigations are conducted.

Effects of altered ration levels on sensory characteristics, lipid content and fatty acid composition of rainbow trout (Oncorhynchus mykiss)

Effects of altered ration levels on sensory characteristics, lipid content and fatty acid composition of rainbow trout (Oncorhynchus)

Effects of Starvation on Rainbow Trout Muscle

Abstract This study deals with the effects of up to three months starvation on white and red muscle in mature and immature rainbow trout. Examined in the study were the histochemistry of the muscle, the dynamics of muscle fiber growth, key enzymes involved in energy metabolism and the chemical composition. Muscle fibers in the different muscle tissues did not respond to starvation in a consistent way. In red muscle starvation induced a narrowing of the range of fiber sizes, regardless of the stage of maturation of the fish. In white muscle of immature fish starvation for 3 months had no effect on fiber sizes whereas in sexually mature fish the fiber cross section areas were smaller than expected based on the weight of the fish. This was probably caused by a pronounced break down of muscle protein in mature fish for gonad formation and energy production without a simultaneous replacement of protein by water. Pink muscle in immature fish showed a response intermediate between red and white muscle. Starvatio...

Effects of reduced feed ration levels on fat content and fatty acid composition in white and red muscle from rainbow trout

Abstract The effects of different ration levels (RL) on lipid content and composition in red and white muscle of rainbow trout (Salmo gairdneri Rich.) were investigated in a study lasting from start-feeding throughout life. Three experimental ration levels, adequate feeding, moderate restriction and strong restriction, were defined according to expected growth. Groups of trout were maintained at constant experimental ration levels, or subjected to changed levels. In this paper results from the first year of the ongoing experiment are presented. Total fat content was low in white and high in red muscle, with only minor differences between the groups. The fat content of the dorsal fat depot, however, was very low when RL was low but rose with increasing rations. The amount of saturated fatty acids was about the same in white and red muscle. Monounsaturated fatty acids were higher, whereas polyunsaturated fatty acids were lower, in red than in white muscle. Changing RL caused changes in mono- and polyunsaturated fatty acids in white as well as in red muscle, especially in the groups where RL was reduced from high to low and increased from low to high. This was particularly evident for the monounsaturated fatty acids 16:1, 18:1, 20:1 and 22:1 and the polyunsaturated acids 20:5 and 22:6. The fatty acid composition in muscle deviated from that of the feed. Thus, the content of 16:0, 18:1 and 22:6 was high, whereas 20:1, 22:1 and 20:5 were low in muscle compared to feed.