Cardiac responses to elevated seawater temperature in Atlantic salmon

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Spawning manipulation, broodfish diet feeding and egg production in farmed Atlantic salmon

Atlantic salmon aquaculture relies on continuous supply of high quality eggs. Broodfish nutrition and manipulation of ovulation time (photoperiod and temperature) are key factors. The optimum feeding period with broodfish diet has not been investigated before. The present study examined how feeding period with broodfish diet (9 vs. 17 months) interacted with manipulation of ovulation time (early (Nov), normal (Dec), late (Feb)) on broodstock egg production capacity and egg quality in two-sea-winter female Atlantic salmon (∼12 kg). All groups were fed until June 2021 when they were transferred to tanks and starved until ovulation.publishedVersio

Lens GSH metabolism.

<p>Relative levels of metabolites related to GSH metabolism in lenses from Atlantic salmon and rainbow trout reared at 13 or 19°C at the end of the 35d experiment: (A) 5-oxoproline, (B) cystathionine, (C) glutamate, (D) 2-aminobutyrate, (E) ophtalmate, (F) oxidized glutathione (GSSG), (G) reduced glutathione (GSH). Significant differences between species are denoted by an asterisk (*), significant differences between temperatures and interaction effects are denoted by lower case letters (a, b) (p<0.05).</p

Lens metabolomic profiling as a tool to understand cataractogenesis in Atlantic salmon and rainbow trout reared at optimum and high temperature

<div><p>Periods of high or fluctuating seawater temperatures result in several physiological challenges for farmed salmonids, including an increased prevalence and severity of cataracts. The aim of the present study was to compare cataractogenesis in Atlantic salmon (<i>Salmo salar</i> L.<i>)</i> and rainbow trout (<i>Oncorhynchus mykiss</i>) reared at two temperatures, and investigate whether temperature influences lens metabolism and cataract development. Atlantic salmon (101±2 g) and rainbow trout (125±3 g) were reared in seawater at either 13°C (optimum for growth) or 19°C during the 35 days experiment (n = 4 tanks for each treatment). At the end of the experiment, the prevalence of cataracts was nearly 100% for Atlantic salmon compared to ~50% for rainbow trout, irrespective of temperature. The severity of the cataracts, as evaluated by slit-lamp inspection of the lens, was almost three fold higher in Atlantic salmon compared to rainbow trout. The global metabolic profile revealed differences in lens composition and metabolism between the two species, which may explain the observed differences in cataract susceptibility between the species. The largest differences were seen in the metabolism of amino acids, especially the histidine metabolism, and this was confirmed by a separate quantitative analysis. The global metabolic profile showed temperature dependent differences in the lens carbohydrate metabolism, osmoregulation and redox homeostasis. The results from the present study give new insight in cataractogenesis in Atlantic salmon and rainbow trout reared at high temperature, in addition to identifying metabolic markers for cataract development.</p></div

Lens histidine and N-Acetylhistidine (NAH) concentrations.

<p>(A) Lens histidine and (B) NAH concentrations in lenses from Atlantic salmon and rainbow trout reared at 13 or 19°C at the end of the 35d experiment, as mean ± SEM (n = 4). Significant differences between the species are denoted by an asterisk (*), significant differences between temperatures and interaction effects are denoted by lower case letters (a, b) (p<0.05).</p

Lens lipid metabolism.

<p>Relative levels of metabolites related to the lipid metabolism in lenses from Atlantic salmon and rainbow trout reared at 13 or 19°C at the end of the 35d experiment: (A) prostaglandin E₂, (B) arachidonate (20:4n-6), (C) carnitine, (D) acetylcarnitine, (E) sphingosine. Significant differences between species are denoted by an asterisk (*), significant differences between temperatures are denoted by lower case letters (a, b) (p<0.05).</p

Lens histidine and N-Acetylhistidine (NAH) levels.

<p>(A) Relative levels of histidine and (B) NAH in lenses from Atlantic salmon and rainbow trout reared at 13 or 19°C at the end of the 35d experiment. Significant differences between the species are denoted by an asterisk (*), significant differences between temperatures and interaction effects are denoted by lower case letters (a, b) (p<0.05).</p

Statistical modelling of voluntary feed intake in individual Atlantic salmon (Salmo salar L.)

Precision feeding aims to provide the correct amount of feed to farmed animals for optimal growth and performance and to avoid feed waste. However, knowledge underlying the meal-to-meal variability in voluntary feed intake of farmed species is still limited. This study examined the relationship between meals, feed deprivation time and the feed (pellets) consumed by Atlantic salmon post smolts. The data was collected from individual fish handfed to satiety without social interaction in three independent short-term (6-12 days) experiments. The fixed variables of our model (feed deprivation time (i.e., time between meals), number of pellets provided, day, previous meal size, and fish growth) explained most of the feed intake (number of pellets ingested) (R2 0.68). Results show that fish ingested more pellets over the course of the trials as they grew, resulting in a positive correlation between feed intake and fish growth (final minus initial fish weight). The time between meals and prior meal size (the number of pellets ingested in the previous meal) significantly affected feed intake in the following meal. Our results suggest that it is possible to optimise meal size by considering the size of the previous meal and the time since it was given.publishedVersio

Lens carbohydrate metabolism.

<p>Relative levels of metabolites involved in glycolysis and the polyol pathway in lenses from Atlantic salmon and rainbow trout reared at 13 or 19°C at the end of the 35d experiment: (A) sorbitol, (B) fructose, (C) glucose-6-phosphate, (D) nicotinamide adenine dinucleotide (NAD+). Significant differences between species are denoted by an asterisk (*), significant differences between temperatures and interaction effects are denoted by lower case letters (a, b) (p<0.05).</p

Lens N-Acetylaspartate (NAA) levels.

<p>(A) Relative levels of NAA in lenses from Atlantic salmon and rainbow trout reared at 13 or 19°C at the end of the 35d experiment, and (B) NAA levels in relation to cataract score (mean level for lenses scored 0–3 for each of the species, T: trout, S: salmon) Significant differences between species are denoted by an asterisk (*), significant differences between temperatures and interaction effects are denoted by lower case letters (a, b) (p<0.05).</p