Universidad Austral de Chile

Sustainable mitigation of piscirickettsiosis, the leading infectious cause of mortality in Chilean salmon aquaculture and a key driver of antibiotic dependence, demands green alternatives that fortify the intestinal health of fish. Here we show that brewer's spent grain (BSG), an abundant lignocellulosic by-product, can be upgraded into a functional feed additive through a fully aqueous, green-chemistry workflow comprising enzymatic hydrolysis with cellulase/hemicellulase, microwave-vacuum drying, and ultrasound-assisted water extraction. The process yields a solvent-free extract [bagasse extract-PBS (BEP)1860 μg/mL gallic acid equivalents (GAE)] that preserves ≥90 % RTgutGC cell viability up to 35 μg/mL GAE. A 24 h pre-exposure of rainbow trout intestinal epithelial cells to 5-25 μg/mL GAE of BEP markedly enhanced the inflammatory response (il-1β and il-8 up-regulated up to 4.3-fold), strengthened barrier integrity (zo-1 up-regulated 3.1-fold), and activated antioxidant defenses (sod, gpx, gr elevated 2-5-fold). Importantly, pre-treatment with 25-100 μg/mL GAE of BEP curtailed Piscirickettsia salmonis induced cellular lysis by ∼45 % and reduced bacterial translocation across epithelial monolayers by ∼1 log CFU, with the strongest protection against the prevalent EM-90-like genotype. This is the first report demonstrating that an agro-industrial residue can be converted, within a biocircular and sustainable-pharmacy framework, into an immunonutraceutical capable of simultaneously promoting the optimal immune system activation, the modulation of intercellular junctions, and the oxidative stress in this intestinal epithelial cell line. The present study suggests the use of BEP as a potential additive capable of modulating innate immune responses and contributing to future mitigation of the impact of P. salmonis infection. However, further studies are necessary to test this important issue for the aquaculture industry in Chile.

The Gram-negative facultative intracellular pathogen Piscirickettsia salmonis infects salmonid fish species and causes economic losses in the Chilean salmon farming industry. Until now, the virulence factors and the mechanisms involved in establishing the fish infection are scarcely understood. P. salmonis can infect and survive in salmonid macrophages, and reports have shown that the Icm/Dot type-IV secretion system is part of the virulence factors that are essential for bacterial infection and replication inside bacteria-induced vacuoles. Since the Icm/Dot substrate SdhA has been identified as a key protein factor in maintaining the integrity of the Legionella-induced vacuolar membrane, we seek to explore the possibility that this substrate can also play a role in P. salmonis infection in fish. In this study we first confirmed the presence of the orthologous gene encoding SdhA of P. salmonis, demonstrating an evolutionary relationship with the sdhA genes of Coxiella burnetii and Legionella pneumophila. The in-silico analysis of the protein revealed a conserved structure and short linear motifs that suggest several potential functions related to vacuolar stability, autophagy, apoptosis, and vesicular transport processes that probably enable the pathogen to manipulate the defense mechanisms of the host cell. Additionally, for the first time, we demonstrated the early expression of sdhA at both the transcript and protein levels in infected salmon cells, suggesting that SdhA could interfere with the host pathogen eradication mechanisms shortly after infection. These results set up the basis to further studies on the functional role of SdhA in the host-pathogen interaction mechanisms associated with P. salmonis infection of salmonid fish.

To accurately predict breeding values, genetic evaluations must define an appropriate model that considers the main factors influencing the traits of interest. The challenge increases in crossbreeding populations, such as those found in Chile, where multiple breeds, including those from different countries, are used. In particular, the country of origin is not currently incorporated into genetic models used in Chile. The objectives of this study were 2-fold: (1) to evaluate different genetic models of increasing complexity to determine if the inclusion of a specific strain classification, strain proportions in crossbred animals, and heterosis effects could enhance genetic evaluations compared with the current model used in Chile; and (2) to determine the presence of heterosis effects among specific dairy genetic strains when crossed with Chilean Friesian cows, focusing on annual milk, fat, and protein production; SCS; and calving interval. A dataset of 1,429,132 records from 586,624 cows that calved between 1998 and 2018 was provided by the Chilean Agricultural and Services Cooperative (COOPRINSEM; Osorno, Chile). Using pedigree information, the proportion of each cattle breed according to its different countries of origin (genetic strain) was calculated for each animal. Subsequently, strains concerning Chilean Friesian cows were selected with a wide range of proportions. The final dataset included 8 strains: Chilean Friesian, French Holstein-Friesian, US-Holstein, US-Jersey, French Montbéliarde, New Zealand Holstein-Friesian, Swedish Red and White, and British Friesian, representing 369,755 observations collected between 2009 and 2018. Production (milk, fat, and protein production per lactation) and functional traits (SCS and calving interval) were also provided by COOPRINSEM. Four different models were tested: the current model using only 5 breed categories based on physical appearance (M1), a more precise classification considering 8 dairy strains categories (M2), M2 plus the inclusion of a cross-classified effect of crossbreeding proportion with strain categories (M3), and M3 plus the cross-classified effect of heterosis level with strain categories (M4). Our results show that M4 was the best model for analyzing information on crossbred dairy cows from Chile. Our study also suggests that there are specific effects for some strains, as well as heterosis effects between several strains and the Chilean Friesian.