Publications by authors named "Malcolm Jobling"

6 Publications

  • Page 1 of 1

Digestive tract morphology and enzyme activities of juvenile diploid and triploid Atlantic salmon (Salmo salar) fed fishmeal-based diets with or without fish protein hydrolysates.

PLoS One 2021 11;16(1):e0245216. Epub 2021 Jan 11.

Faculty of Biosciences, Fisheries and Economics, UiT - the Arctic University of Norway, Tromsø, Norway.

Triploid, sterile Atlantic salmon (Salmo salar) could make a contribution to the development of the farming industry, but uncertainties about the performance and welfare of triploids have limited their adoption by farmers. In this study, we compared the ontogeny of digestive tract morphology and enzyme activities (pepsin, trypsin, chymotrypsin, alkaline phosphatase and aminopeptidase) of diploid and triploid Atlantic salmon. Fish were fed diets based on fishmeal (STD) or a mix of fishmeal and hydrolysed fish proteins (HFM) whilst being reared at low temperature from start-feeding to completion of the parr-smolt transformation. Fish weights for each ploidy and feed combination were used to calculate thermal growth coefficients (TGCs) that spanned this developmental period, and the data were used to examine possible relationships between enzyme activities and growth. At the end of the experiment, faeces were collected and analyzed to determine the apparent digestibility coefficients (ADCs) of the dietary amino acids (AAs). Digestive tract histo-morphology did not differ substantially between ploidies and generally reflected organ maturation and functionality. There were no consistent differences in proteolytic enzyme activities resulting from the inclusion of HFM in the diet, nor was there improved digestibility and AA bioavailability of the HFM feed in either diploid or triploid fish. The triploid salmon had lower ADCs than diploids for most essential and non-essential AAs in both diets (STD and HFM), but without there being any indication of lower intestinal protease activity in triploid fish. When trypsin-to-chymotrypsin activity and trypsin and alkaline phosphatase (ALP) ratios (T:C and T:ALP, respectively) were considered in combination with growth data (TGC) low T:C and T:ALP values coincided with times of reduced fish growth, and vice versa, suggesting that T:C and T:ALP may be used to predict recent growth history and possible growth potential.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245216PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7801030PMC
January 2021

Growth and development of skeletal anomalies in diploid and triploid Atlantic salmon (Salmo salar) fed phosphorus-rich diets with fish meal and hydrolyzed fish protein.

PLoS One 2018 22;13(3):e0194340. Epub 2018 Mar 22.

Faculty of Biosciences, Fisheries and Economics, University of Tromsø -the Arctic University of Norway, Tromsø, Norway.

Diploid and triploid Atlantic salmon, Salmo salar were fed high-protein, phosphorus-rich diets (56-60% protein; ca 18g phosphorus kg-1 diet) whilst being reared at low temperature from start-feeding until parr-smolt transformation. Performances of salmon fed diets based on fish meal (STD) or a mix of fishmeal and hydrolysed fish proteins (HFM) as the major protein sources were compared in terms of mortality, diet digestibility, growth and skeletal deformities. Separate groups of diploids and triploids were reared in triplicate tanks (initially 3000 fish per tank; tank biomass ca. 620 g) from 0-2745 degree-days post-start feeding (ddPSF). Growth metrics (weight, length, condition factor) were recorded at ca. 4 week intervals, external signs of deformities to the operculum, jaws and spinal column were examined in parr sampled at 1390 ddPSF, and external signs of deformity and vertebral anomalies (by radiography) were examined in fish sampled at the end of the trial (2745 ddPSF). The triploid salmon generally had a lower mass per unit length, i.e. lower condition factor, throughout the trial, but this did not seem to reflect any consistent dietary or ploidy effects on either dietary digestibility or the growth of the fish. By the end of the trial fish in all treatment groups had achieved a weight of 50+ g, and had completed the parr-smolt transformation. The triploids had slightly, but significantly, fewer vertebrae (Triploids STD 58.74 ± 0.10; HFM 58.68 ± 0.05) than the diploids (Diploids STD 58.97 ± 0.14; HFM 58.89 ± 0.01), and the incidence of skeletal (vertebral) abnormalities was higher in triploids (Triploids STD 31 ± 0.90%; HFM 15 ± 1.44%) than in diploids (Diploids STD 4 ± 0.80%; HFM 4 ± 0.83%). The HFM diet gave a significant reduction in the numbers of triploid salmon with vertebral anomalies in comparison with the triploids fed the STD diet possibly as a result of differences in phosphorus bioavailability between the two diets. Overall, the incidence of skeletal deformities was lower than reported in previous studies (Diploids 20+%, Triploids 40+%), possibly as a result of the combination of rearing at low-temperature and phosphorus-rich diets being used in the present study.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0194340PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864013PMC
July 2018

Seasonal Differences in Relative Gene Expression of Putative Central Appetite Regulators in Arctic Charr (Salvelinus alpinus) Do Not Reflect Its Annual Feeding Cycle.

PLoS One 2015 30;10(9):e0138857. Epub 2015 Sep 30.

Department of Arctic and Marine Biology, UiT-The Arctic University of Norway, Tromsø, Norway.

The highly seasonal anadromous Arctic charr (Salvelinus alpinus) was used to investigate the possible involvement of altered gene expression of brain neuropeptides in seasonal appetite regulation. Pro-opiomelanocortin (POMCA1, POMCA2), Cocaine and amphetamine regulated transcript (CART), Agouti related Peptide (AgRP), Neuropeptide Y (NPY) and Melanocortin Receptor 4 (MC4-R) genes were examined. The function of centrally expressed Leptin (Lep) in fish remains unclear, so Lep (LepA1, LepA2) and Leptin Receptor (LepR) genes were included in the investigation. In a ten months study gene expression was analysed in hypothalamus, mesencephalon and telencephalon of immature charr held under natural photoperiod (69°38'N) and ambient temperature and given excess feed. From April to the beginning of June the charr did not feed and lost weight, during July and August they were feeding and had a marked increase in weight and condition factor, and from November until the end of the study the charr lost appetite and decreased in weight and condition factor. Brain compartments were sampled from non-feeding charr (May), feeding charr (July), and non-feeding charr (January). Reverse transcription real-time quantitative PCR revealed temporal patterns of gene expression that differed across brain compartments. The non-feeding charr (May, January) had a lower expression of the anorexigenic LepA1, MC4-R and LepR in hypothalamus and a higher expression of the orexigenic NPY and AgRP in mesencephalon, than the feeding charr (July). In the telencephalon, LepR was more highly expressed in January and May than in July. These results do not indicate that changes in central gene expression of the neuropeptides investigated here directly induce seasonal changes in feeding in Arctic charr.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0138857PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4589418PMC
May 2016

Long-term fasting in the anadromous Arctic charr is associated with downregulation of metabolic enzyme activity and upregulation of leptin A1 and SOCS expression in the liver.

J Exp Biol 2013 Sep 16;216(Pt 17):3222-30. Epub 2013 May 16.

Faculty of Biosciences, Fisheries and Economy, Department of Arctic and Marine Biology, University of Tromsø, Tromsø, Norway.

The life strategy of the anadromous Arctic charr (Salvelinus alpinus) includes several months of voluntary fasting during overwintering in freshwater, leading to emaciation prior to seawater migration in spring. In this study we compared changes in condition, substrate utilization and liver metabolism between captive anadromous charr subjected to food deprivation during late winter and spring, and conspecifics fed in excess. In March, nine out of the 10 sampled fed fish had not eaten, indicating that they were in a voluntary anorexic state. In June, the fed fish were eating and all had higher body mass, condition factor and adiposity than in March. In fasted fish there were only small decreases in body mass, condition factor and adiposity between March and May, but all these parameters decreased markedly from May to June. The fasted fish were depleted in fat and glycogen in June, had suppressed activity of hepatic enzymes involved in lipid metabolism (G6PDH and HOAD) and seemed to rely on protein-derived glucose as a major energy source. This was associated with upregulated liver gene expression of leptin A1, leptin A2, SOCS1, SOCS2 and SOCS3, and reduced IGF-I expression. In an in vitro study with liver slices it was shown that recombinant rainbow trout leptin stimulated SOCS1 and SOCS3 expression, but not SOCS2, IGF-I or genes of enzymes involved in lipid (G6PDH) and amino acid (AspAT) metabolism. It is concluded that liver leptin interacts with SOCS in a paracrine fashion to suppress lipolytic pathways and depress metabolism when fat stores are depleted.
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http://dx.doi.org/10.1242/jeb.088344DOI Listing
September 2013

Seasonal appetite regulation in the anadromous Arctic charr: evidence for a role of adiposity in the regulation of appetite but not for leptin in signalling adiposity.

Gen Comp Endocrinol 2012 Sep 23;178(2):330-7. Epub 2012 Jun 23.

Faculty of Biosciences, Fisheries and Economy, University of Tromsø, N-9037 Tromsø, Norway.

The aim of this study was to investigate whether the seasonal feeding cycle of the anadromous Arctic charr (Salvelinus alpinus) is regulated by a lipostatic mechanism and if leptin (Lep) might act as an endocrine signal of adiposity. Offspring of anadromous Arctic charr with a body mass of 121 g were divided into two treatment groups; one was given feed in excess from March to November, and the other was fasted between April and early June and fed in excess thereafter. In the continuously fed group there was an 8-fold increase in body mass, and a doubling of percentage body fat, from March to August, after which there was no further increase. Fish in the other group lost weight and body fat during fasting, but grew rapidly on being fed, and had partially compensated for their deficit in body mass by August. Differences in percentage body fat between treatment groups were eliminated by August, providing evidence for a lipostatic regulation of feeding and energy homeostasis in Arctic charr. Neither liver total LepA gene expression nor plasma Lep concentrations correlated positively with fish adiposity, so there was no evidence that Lep acts as a signal of adiposity in this species. On the other hand, there was a strong increase in liver LepA1 gene expression at the end of the fasting period, concomitant with fat mobilization and increased plasma glucose, indicating that LepA1 may play a role in regulating metabolic processes associated with fasting.
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http://dx.doi.org/10.1016/j.ygcen.2012.06.017DOI Listing
September 2012

Polychlorinated biphenyl toxicokinetics and P4501A responses in anadromous Arctic charr during winter emaciation.

Environ Toxicol Chem 2002 Aug;21(8):1745-52

Norwegian Institute for Nature Research, Polar Environmental Centre, Tromsø.

Polychlorinated biphenyl (PCB) toxicokinetics and hepatic P450 (CYP) 1A activities were studied in wild anadromous Arctic charr (Salvelinus alpinus) during winter emaciation. The fish were captured as they returned from summer feeding in seawater and were held without food over winter. In September the fish were given a single, oral dose of either 0 (control), 0.1, 1, or 50 microg PCB/g fish. During winter a net loss of PCB occurred from the carcass (including gut), whereas net inputs and increases in concentrations of PCB in the liver and brain occurred with increases in brain PCB concentrations being up to 10-fold. Hepatic CYP1A activities were positively correlated with the PCB dose in October. In the fish given 1 mg PCB/kg fish in September, however, a 12-fold increase in CYP1A activity occurred from October to May. This increase in CYP1A activity was observed during a period in which the body burden of PCB decreased by 20%. These results demonstrate that interpretations of the CYP1A biomarker response must be made with caution. Overall, the findings point to potentiated risks of biological effects of PCB during periods of emaciation.
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August 2002