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

• Published in: PeerJ
• Main Authors: Selvam, Chandrasekar, Powell, Mark D., Liland, Nina S., Rosenlund, Grethe, Sissener, Nini H.
• Other Authors: Norwegian Seafood Research Fund—FHF, Norwegian Research Council—NRC
• Format: Article in Journal/Newspaper
• Language: English
• Published: PeerJ 2021
• Subjects: Gata; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.7717/peerj.12028; https://peerj.com/articles/12028.pdf; https://peerj.com/articles/12028.xml; https://peerj.com/articles/12028.html

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 PGE 2 -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.