Schizochytrium sp. (T18) Oil as a Fish Oil Replacement in Diets for Juvenile Rainbow Trout (Oncorhynchus mykiss): Effects on Growth Performance, Tissue Fatty Acid Content, and Lipid-Related Transcript Expression

Influence of a Mixture of Protein Hydrolysate from Black Soldier Fly Larvae and Schizochytrium on Palatability, Plasma Biochemistry, and Antioxidative and Anti-Inflammatory Capacity in Cat Diets

The objective of this research was to evaluate palatability, plasma biochemistry, antioxidative and anti-inflammatory capacity, and immune levels in cats by feeding supplementing inclusion of different levels of a mixture of protein hydrolysate from black soldier fly larvae and schizochytrium (BSFPs) in diets. In the feed experiment, a total of 24 adult cats (12 females and 12 males; BW: 3.02 ± 0.06 kg) were randomly divided into four groups: (1) diet with chicken and fish meal as primary protein resource (CON); (2) diet with 5% BSFPs replacing chicken meal, fish meal, chicken oil, and fish oil (5% BSFPs); (3) 10% BSFPs; and (4) 15% BSFPs. The body weight and feed intake were recorded, and a blood sample was collected for analysis. In the palatability experiment, three diets containing 5%, 10%, and 15% BSFPs were evaluated by comparing with CON. These results suggested that different levels of BSFPs could improve palatability in cat diets by enhancing the first sniff, the first bite, and feed intake (p < 0.05). However, no significant influence existed in body weight and average daily feed intake (p > 0.05). In comparison to the CON group, 5% and 15% BSFPs significantly increased the total protein content, and all treatment groups decreased the triglyceride content and enhanced the calcium concentration in plasma; in addition, the activity of aspartate aminotransferase and alanine aminotransferase and the content of creatinine and urea nitrogen were significantly reduced by the supplementation inclusion of BSFPs in the diets (p < 0.05). The enzyme activity of glutathione peroxidase was dramatically enhanced by the supplementation of 10% and 15% BSFPs in diets compared with the CON diet, and the activity of superoxide dismutase was increased and the malondialdehyde concentration was remarkably reduced in all three treatments (p < 0.05). Compared with the CON group, different levels of BSFPs in the diets significantly increased the immunoglobulin A content in plasma; similarly, the immunoglobulin G concentration was significantly enhanced by the supplementation of 10% and 15% BSFPs in the diets (p < 0.05). Furthermore, the interleukin-1β content was significantly reduced in the inclusion of 10% and 15% BSFPs in the diets, and 15% BSFPs remarkably decreased the content of interleukin-8 in plasma compared with the CON diet (p < 0.05). To sum up, the supplementation of different levels of BSFPs exhibited a positive effect on palatability and enhanced the antioxidant, anti-inflammatory, and immune capacity. Particularly, the addition levels of 10% and 15% BSFPs were more effective in antioxidation, anti-inflammation, and immunity.

Metabolomic and Transcriptomic Analysis of Effects of Three MUFA-Rich Oils on Hepatic Glucose and Lipid Metabolism in Mice

SCOPE

Olive oil, rapeseed oil, and lard are dietary fats rich in monounsaturated fatty acids, but the effects of dietary oils enriched in monounsaturated fatty acids on hepatic lipid deposition have seldom been compared.

METHODS AND RESULTS

Ninety 8-week-old C57BL/6J male mice are randomly divided into six groups and fed diets containing lard, rapeseed oil, or olive oil with a 10% or 45% fat energy supply for 16 weeks. Under high-fat conditions, serum total cholesterol levels in the lard and olive oil groups are significantly higher than those in the rapeseed oil group. Hepatic lipid content in the olive oil group is higher than that in the other two groups. Compared with rapeseed oil, lard increases the liver levels of arachidonic, palmitic, and myristic acids and decreases the levels of eicosapentaenoic linolenic acid and linoleic acid. Olive oil increases the liver levels of docosatrienoic, arachidonic, oleic, and myristic acids; maltose; and fructose and decreases the levels of eicosapentaenoic, linolenic, and linoleic acids.

CONCLUSION

Olive oil probably causes hepatic lipid deposition in mice, which may enhance hepatic lipid synthesis by activating the starch and sucrose metabolic pathways. By contrast, rapeseed oil shows a significant anti-lipid deposition effect on the liver.

Effects of Dietary Supplementation with Aurantiochytrium sp. on Zebrafish Growth as Determined by Transcriptomics

The marine protist Aurantiochytrium produces several bioactive chemicals, including EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid), and other critical fish fatty acids. It has the potential to improve growth and fatty acid profiles in aquatic taxa. This study evaluated zebrafish growth performance in response to diets containing 1% to 3% Aurantiochytrium sp. crude extract (TE) and single extract for 56 days. Growth performance was best in the 1% TE group, and therefore, this concentration was used for further analyses of the influence of Aurantiochytrium sp. Levels of hepatic lipase, glucose-6-phosphate dehydrogenase, acetyl-CoA oxidase, glutathione peroxidase, and superoxide dismutase increased significantly in response to 1% TE, while malic enzyme activity, carnitine lipid acylase, acetyl-CoA carboxylase, fatty acid synthase, and malondialdehyde levels decreased. These findings suggest that Aurantiochytrium sp. extract can modulate lipase activity, improve lipid synthesis, and decrease oxidative damage caused by lipid peroxidation. Transcriptome analysis revealed 310 genes that were differentially expressed between the 1% TE group and the control group, including 185 up-regulated genes and 125 down-regulated genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathway analyses of the differentially expressed genes revealed that Aurantiochytrium sp. extracts may influence liver metabolism, cell proliferation, motility, and signal transduction in zebrafish.

Nutritional immunomodulation of Atlantic salmon response to Renibacterium salmoninarum bacterin

We investigated the immunomodulatory effect of varying levels of dietary ω6/ω3 fatty acids (FA) on Atlantic salmon (Salmo salar) antibacterial response. Two groups were fed either high-18:3ω3 or high-18:2ω6 FA diets for 8 weeks, and a third group was fed for 4 weeks on the high-18:2ω6 diet followed by 4 weeks on the high-18:3ω3 diet and termed "switched-diet". Following the second 4 weeks of feeding (i.e., at 8 weeks), head kidney tissues from all groups were sampled for FA analysis. Fish were then intraperitoneally injected with either a formalin-killed Renibacterium salmoninarum bacterin (5 × 107 cells mL-1) or phosphate-buffered saline (PBS control), and head kidney tissues for gene expression analysis were sampled at 24 h post-injection. FA analysis showed that the head kidney profile reflected the dietary FA, especially for C18 FAs. The qPCR analyses of twenty-three genes showed that both the high-ω6 and high-ω3 groups had significant bacterin-dependent induction of some transcripts involved in lipid metabolism (ch25ha and lipe), pathogen recognition (clec12b and tlr5), and immune effectors (znrf1 and cish). In contrast, these transcripts did not significantly respond to the bacterin in the "switched-diet" group. Concurrently, biomarkers encoding proteins with putative roles in biotic inflammatory response (tnfrsf6b) and dendritic cell maturation (ccl13) were upregulated, and a chemokine receptor (cxcr1) was downregulated with the bacterin injection regardless of the experimental diets. On the other hand, an inflammatory regulator biomarker, bcl3, was only significantly upregulated in the high-ω3 fed group, and a C-type lectin family member (clec3a) was only significantly downregulated in the switched-diet group with the bacterin injection (compared with diet-matched PBS-injected controls). Transcript fold-change (FC: bacterin/PBS) showed that tlr5 was significantly over 2-fold higher in the high-18:2ω6 diet group compared with other diet groups. FC and FA associations highlighted the role of DGLA (20:3ω6; anti-inflammatory) and/or EPA (20:5ω3; anti-inflammatory) vs. ARA (20:4ω6; pro-inflammatory) as representative of the anti-inflammatory/pro-inflammatory balance between eicosanoid precursors. Also, the correlations revealed associations of FA proportions (% total FA) and FA ratios with several eicosanoid and immune receptor biomarkers (e.g., DGLA/ARA significant positive correlation with pgds, 5loxa, 5loxb, tlr5, and cxcr1). In summary, dietary FA profiles and/or regimens modulated the expression of some immune-relevant genes in Atlantic salmon injected with R. salmoninarum bacterin. The modulation of Atlantic salmon responses to bacterial pathogens and their associated antigens using high-ω6/high-ω3 diets warrants further investigation.

Recent Advances in Fish Nutrition: Insights on the Nutritional Implications of Modern Formulations

Fish nutrition has driven advances in the efficiency, sustainability, and product quality of aquaculture production, facilitating its expansion of aquaculture production [...]

Comprehensive Analysis of Fatty Acid and Oxylipin Patterns in n3-PUFA Supplements

Supplementing long-chain omega-3 polyunsaturated fatty acids (n3-PUFA) improves health. We characterized the pattern of total and non-esterified oxylipins and fatty acids in n3 supplements made of fish, krill, or micro-algae oil by LC-MS. All supplements contained the declared amount of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA); however, their content per capsule and the concentration of other fatty acids varied strongly. Krill oil contained the highest total n3 oxylipin concentration (6000 nmol/g) and the highest degree of oxidation (EPA 0.7%; DHA 1.3%), while micro-algae oil (Schizochytrium sp.) showed the lowest oxidation (<0.09%). These oils contain specifically high amounts of the terminal hydroxylation product of EPA (20-HEPE, 300 nmol/g) and DHA (22-HDHA, 200 nmol/g), which can serve as an authenticity marker for micro-algae oil. Refined micro-algae and fish oil were characterized by NEFA levels of ≤0.1%. Overall, the oxylipin and fatty acid pattern allows gaining new insights into the origin and quality of n3-PUFA oils in supplements.