Dietary xanthophyll improved growth, antioxidant, pigmentation and meat quality in the southern catfish (Silurus soldatovi meridionalis Chen).

Xanthophyll has multiple physiological functions to improve the quality of farmed animals. The present study aimed to investigate the effects of xanthophyll on the growth performance, antioxidation, immunity, pigmentation and meat quality of southern catfish (Silurus soldatovi meridionalis Chen). Juvenile southern catfish (18.35 ± 0.04 g) were randomly allocated into 24 cages (30 juveniles per cage), and fed diets with different dietary xanthophyll levels (at 14, 42, 80, 108, 126 and 152 mg/kg, dry matter of diet) twice daily for 8 weeks. Results indicated that the diet with 80 mg/kg xanthophyll induced a higher specific growth rate (SGR), feed efficiency ratio and protein productive value. Moreover, the 80 mg/kg xanthophyll diet also increased complement 3, immunoglobulin M (IgM) and lysozyme content more than the other groups. The mRNA expression level of inflammation-related genes and antioxidant enzyme activities further confirmed the effects of 80 mg/kg dietary xanthophyll on improving immune response. The present study also found that the 126 mg/kg xanthophyll diet significantly enhanced the content of total carotenoids and xanthophyll, hydroxyproline, collagen and amino acid in muscle. The diet with 126 mg/kg xanthophylls also induced lower drip loss, thawing loss, centrifugal loss, cooking loss and higher muscle adhesiveness, cohesiveness, springiness, gumminess and chewiness than the other treatments. In conclusion, quadratic regression model analysis based on SGR and IgM revealed that the optimum xanthophyll level in the diet was 86.78 and 84.63 mg/kg, respectively. Moreover, broken line regression analysis based on xanthophyll content in dorsal skin and chewiness in muscle demonstrated that the optimal xanthophyll level was between 89.73 and 108.66 mg/kg in the diet of southern catfish (S. soldatovi meridionalis Chen).

The Loss of focA Gene Increases the Ability of Salmonella Enteritidis to Exit from Macrophages and Boosts Early Extraintestinal Spread for Systemic Infection in a Mouse Model.

Salmonella Enteritidis (SE) can spread from the intestines to cause systemic infection, mainly involving macrophages. Intramacrophage Salmonella exits and reinfects neighboring cells, leading to severe disease. Salmonella genes involved in exiting from macrophages are not well understood or fully identified. A focA::Tn5 mutant was identified by an in vitro assay, with increased ability to exit from macrophages. A defined SEΔfocA mutant and its complemented derivative strain, SEΔfocA::focA, were constructed to confirm this phenotype. Although the lethal ability of focA mutants was similar to that of the parental SE in mice, it was isolated earlier from the liver and spleen than the parental SE. focA mutants induced higher levels of proinflammatory IL-12 and TNF-α compared with the parental SE and SEΔfocA::focA. focA mutants showed higher cytotoxicity and lower formate concentrations than SE and SEΔfocA::focA, whereas there was no change in pyroptosis, apoptosis and flagella formation ability. These current data suggest that the focA gene plays an important role in regulating intramacrophage Salmonella exiting and extraintestinal spread in mice, although the specific mechanism requires further in-depth studies.

Muscle Nutritive Metabolism Changes after Dietary Fishmeal Replaced by Cottonseed Meal in Golden Pompano (Trachinotus ovatus).

Our previous study demonstrated that based on growth performance and feed utilization, cottonseed meal (CSM) could substitute 20% fishmeal (FM) without adverse effect on golden pompano (Trachinotus ovatus). Muscle deposition was also an important indicator to evaluate the efficiency of alternative protein sources. Therefore, the present study was conducted to explore the changes of physiobiochemical and nutrient metabolism in muscle after FM replaced by CSM. Four isonitrogenous and isolipidic experimental diets (42.5% crude protein, 14.0% crude lipid) were formulated to replace 0% (CSM0 diet), 20% (CSM20 diet), 40% (CSM40 diet), and 60% (CSM60 diet) of FM with CSM. Juvenile fish (24.8 ± 0.02 g) were fed each diet for 6 weeks. The results presented, which, compared with the CSM0 diet, CSM20 and CSM40 diets, had no effect on changing the muscle proximate composition and free essential amino acid (EAA) concentration. For glycolipid metabolism, the CSM20 diet did not change the mRNA expression of hexokinase (hk), glucose transport protein 4 (glut4), glucagon-like peptide 1 receptor (glp-1r), while over 20% replacement impaired glucose metabolism. However, CSM20 and CSM40 diets had no effect on altering lipid metabolism. Mechanistically, compared with the CSM0 diet, the CSM20 diet did not change muscle nutritive metabolism through keeping the activities of the nutrient sensing signaling pathways stable. Higher replacement would break this balance and lead to muscle nutritive metabolism disorders. Based on the results, CSM could substitute 20-40% FM without affecting the muscle nutritive deposition. All data supplemented the powerful support for our previous conclusion that CSM could successfully replace 20% FM based on growth performance.