BACKGROUND: The study focused on the impact of Ulva fasciata extract (UFE) supplementation in the diets of Nile tilapia (Oreochromis niloticus) on blood and biochemical markers, immune and oxidative responses, and the expression of related genes, with a specific interest in their condition following exposure to Aeromonas hydrophila.
METHODS: Four different levels of UFE were tested in the diets: 0% (0 mg kg- 1) for the control group (U0), and incremental additions of 0.05% (50 mg kg-1), 0.1% (100 mg kg-1), and 0.15% (150 mg kg-1) for the experimental groups U50, U100, and U150 respectively. Groups of 45 fish weighing 3.126 ± 0.120 g were fed these diets over 90 days.
RESULTS: The study found that groups treated with UFE showed statistically significant enhancements (p < 0.05) compared to the control group. These improvements included increased red and white blood cell counts, higher haemoglobin concentrations, greater packed cell volume, and elevated enzyme activities-specifically, superoxide dismutase, catalase, alanine aminotransferase, and aspartate aminotransferase. Additionally, lysozyme and phagocytic activities were notably higher, especially in the U100 group after exposure. Before exposure to Aeromonas hydrophila, all levels of UFE supplementation led to increased expression of TNF-α and COXII genes and decreased NFκ-B expression. After the challenge, UFE intake resulted in varied expression levels of immune and antioxidant genes (TNF-α, NFκ-B, SOD, and COXII) in the liver, with the most effective responses observed in the U50, U100, and U150 groups.
CONCLUSIONS: The findings underscore the potential of dietary UFE as a natural antioxidant and immune booster for Nile tilapia.

Serum amyloid A (SAA) proteins belong to a family of acute-phase reactants, playing an integral role in defending the organism from pathological damage. Despite a wealth of data on the regulation of SAA transcripts in teleosts, there is only limited information on these proteins\' abundance in fish. The aim of this study is to characterise SAA protein levels in salmonids using a newly developed antibody specific to salmonid SAA. The salmonid SAA antibody detected SAA and accurately discriminated between stimulated and control specimens from rainbow trout macrophage cell line (RTS-11) in vitro, as well as rainbow trout challenged with Aeromonas salmonicida- or flagellin-stimulated Atlantic salmon in vivo. The presence of SAA protein was analysed in RTS-11 cell line supernatants, liver, and spleen samples using ELISA, immunoblotting, and immunohistochemistry. This study is the first to characterise SAA protein levels in salmonids in vivo and in vitro. The newly developed salmonid SAA antibody was able to discriminate between stimulated and unstimulated specimens, showing that it can be used to study the acute-phase response in salmonids with the potential to be further developed into assays to monitor and evaluate health in wild and farmed fish.

The growth of aquaculture, both in terms of the volume of production and the diversity of species and production systems, has created challenges for effective animal health policies. This paper presents results of a case study of the costs to a sector of U.S. aquaculture in which producers raising fish that are sold and shipped live contend with widely differing requirements for testing and certification of aquatic animal health. These are compared to related costs under a proposed uniform standard. The uniform standard scenario assumes adoption by the majority of the industry of a non-regulatory surveillance and biosecurity program with veterinary oversight, as an alternative to the current complex regulatory environment based on administrative political districts rather than on risk of disease transmission. Farm-level cost data were obtained through a survey that captured 74% of the national volume of baitfish and sportfish production in the U.S. Reflecting recent joint industry/federal efforts to develop a non-regulatory national U.S. program to set and verify a uniform standard for aquatic animal health, seven scenarios were modelled to determine the potential benefits and costs of such a program. Results showed that the net benefit of a uniform standard, if adopted nationally, could result in an estimated annual savings of $6.6 million to the U.S. baitfish and sportfish industry, and an average savings of $81,175/farm (with a range of $17,851/farm to $265,968/farm). Such cost savings provide an incentive for producers to support the program. Moreover, development of a uniform standard has potential to move aquatic animal health policies from the current framework of political administrative units to one based on epidemiological approaches and sound science.