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Haematological and intestinal health parameters of rainbow trout are influenced by dietary live yeast and increased water temperature

Journal article
Authors D. Huyben
A. Vidakovic
Henrik Sundh
Kristina Sundell
A. Kiessling
T. Lundh
Published in Fish and Shellfish Immunology
Volume 89
Pages 525-536
ISSN 1050-4648
Publication year 2019
Published at Department of Biological and Environmental Sciences
Pages 525-536
Language en
Keywords Blood biochemistry, Gene expression, Heat stress, Histology, qPCR, Saccharomyces cerevisiae, Salmonids, claudin 6, fish protein, gamma interferon, heat shock protein, hemoglobin, hot water, hydrocortisone, interleukin 8, occludin, protein ZO1, transforming growth factor beta, tricellulin, tumor necrosis factor, animal cell, animal experiment, animal tissue, Article, chronic stress, colony forming unit, controlled study, edema, erythrocyte count, fish meal, food intake, hematocrit, hematology, hemoglobin blood level, hydrocortisone blood level, innate immunity, intestine, intestine injury, intestine villus, lamina propria, mean corpuscular hemoglobin, mean corpuscular volume, nonhuman, Oncorhynchus mykiss, oxygen consumption, priority journal, temperature stress, water temperature
Subject categories Marine ecology


Live yeast may be a sustainable protein source in salmonid diets while exhibiting a probiotic effect to counteract environmental stressors, such as increased water temperature that is being exacerbated by climate change. The objective of this study was to evaluate the effects of feeding a high dietary inclusion of live yeast and increased water temperature on growth, haematological and intestinal physiology of rainbow trout. For six weeks, 129 g fish in 16 tanks (n = 4) were fed either a diet based on fishmeal or based on live yeast (214 g kg −1 of diet or 7.6 log CFU g −1 of Saccharomyces cerevisiae) that replaced 40% of fishmeal protein while fish were reared in water temperatures of either 11 °C (cold) or 18 °C (warm). Fish weights, caudal blood and proximal and distal intestines were collected and analysed. Fish fed live yeast resulted in reduced growth (SGR and WG) and higher FCR, while growth in cold and warm water was similar despite differences in TGC. However, increased mortality, plasma cortisol, and intestinal oedema and villous damage indicated fish reared in warm water were subjected to chronic stress. Temperature had a significant effect on haematocrit and red blood cell counts that resulted in significantly higher haemoglobin levels in fish kept in warm water attributed to an elevated oxygen demand. In the proximal intestine, increased temperature resulted in reduced expression of pro-inflammatory cytokines, e.g. TNFα and IL8, that were further reduced in fish fed live yeast. In addition, feeding live yeast reduced gene expression of CLD6 involved in gut barrier function, which suggests that the level of yeast was too high and masked any beneficial effects on fish health. In conclusion, feeding a high inclusion of live yeast reduced fish growth and expression of intestinal genes, while increasing the temperature from 11 to 18 °C subjected fish to chronic stress that restricted growth, suppressed innate immunity and induced intestinal damage. Replacing 40% of fishmeal protein with live yeast did not counteract negative effects caused by increased temperature, thus alternative strategies need to be explored and implemented to protect the growth and health of rainbow trout from seasonal and long-term rises in water temperature. © 2019

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