Impact of dietary level and ratio of n-6 and n-3 fatty acids on disease progression and mRNA expression of immune and inflammatory markers in Atlantic salmon (Salmo salar) challenged with Paramoeba perurans

Abstract

The aim of the study was to investigate the influence of dietary level and ratio of n-6/n-3 fatty acids (FA) on growth, disease progression and expression of immune and inflammatory markers in Atlantic salmon (Salmo salar) following challenge with Paramoeba perurans. Fish (80 g) were fed four different diets with different ratios of n-6/n-3 FA; at 1.3, 2.4 and 6.0 and one diet with ratio of 1.3 combined with a higher level of n-3 FA and n-6 FA. The diet with the n-6/n-3 FA ratio of 6.0 was included to ensure potential n-6 FA effects were revealed, while the three other diets were more commercially relevant n-6/n-3 FA ratios and levels. After a pre-feeding period of 3 months, fish from each diet regime were challenged with a standardized laboratory challenge using a clonal culture of P. perurans at the concentration of 1,000 cells L−1. The subsequent development of the disease was monitored (by gross gill score), and sampling conducted before challenge and at weekly sampling points for 5 weeks post-challenge. Challenge with P. perurans did not have a significant impact on the growth of the fish during the challenge period, but fish given the feed with the highest n-6/n-3 FA ratio had reduced growth compared to the other groups. Total gill score for all surfaces showed a significant increase with time, reaching a maximum at 21 days post-challenge and declined thereafter, irrespective of diet groups. Challenge with P. perurans influenced the mRNA expression of examined genes involved in immune and inflammatory response (TNF-α, iNOS, IL4-13b, GATA-3, IL-1β, p53, COX2 and PGE2-EP4), but diet did not influence the gene expression. In conclusion, an increase in dietary n-6/n-3 FA ratio influenced the growth of Atlantic salmon challenged with P. perurans; however, it did not alter the mRNA expression of immune genes or progression of the disease.

Comparison of Different Dietary Fatty Acids Supplement on the Immune Response of Hybrid Grouper (Epinephelus fuscoguttatus × Epinephelus lanceolatus) Challenged with Vibrio vulnificus

“…They revealed that a diet containing 2% of LN and LA showed significantly higher phagocytic and respiratory burst activities compared with the other treatments with lower levels of pure fatty acids of LN or LA. On the contrary, in other studies, the intake of more than 2% of the total prepared feed formulation of fatty acids, such as n-3 or n-6 PUFAs, may suppress the immune responses of several fishes, including juvenile golden pompano, Trachinotus ovatus [ 51 ] and Atlantic salmon, Salmo salar [ 52 ]. In the present study, grouper fed with a diet containing 2% oleic acid showed significantly higher immune responses among the treatment groups in pre- and post-bacterial challenge conditions.…”

Triacylglycerols and Other Lipids Profiling of Hemp By-Products

“…Human beings evolved on a diet with a ratio of ω-6/ω-3 essential fatty acids of 1 whereas in Western diets the ratio is 15/1 to 16.7/1; a lower ratio of ω-6/ω-3 is needed for the prevention and management of chronic diseases [ 34 ]. A study suggested that an increase in the dietary ω-6/ω-3 ratio was reported to influence the growth of Atlantic salmon challenged with Paramoeba perurans [ 35 ]. The ω-6/ω-3 fatty acid ratio of oils extracted from hemp cake and hemp hulls was 3.0:1 and 3.1:1, respectively.…”

Long-term feeding of Atlantic salmon with varying levels of dietary EPA + DHA alters the mineral status but does not affect the stress responses after mechanical delousing stress

“…The beneficial effects of dietary n-3 LC-PUFA on immune functions are well documented in many vertebrates (2)(3)(4) , including Atlantic salmon (5,6,8) . However, many studies in Atlantic salmon have found no detrimental effects on health and immune functions when fed low dietary n-3 LC-PUFA (71)(72)(73) . Similarly, in this current study, dietary EPA þ DHA level did not alter the mRNA expression of analysed immune genes (IFN-γ, TNF-α, TGF-β and IL4/13a).…”

“…Similarly, in this current study, dietary EPA þ DHA level did not alter the mRNA expression of analysed immune genes (IFN-γ, TNF-α, TGF-β and IL4/13a). As pointed out by others (71,73,74) , the dietary manipulation of gene expression is not always straightforward. It may also be influenced by various other factors, which include ingredient composition, duration of feeding, species, studied tissue, rearing conditions and other environmental factors.…”