Dietary Vitamin A Improved the Flesh Quality of Grass Carp (Ctenopharyngodon idella) in Relation to the Enhanced Antioxidant Capacity through Nrf2/Keap 1a Signaling Pathway

Fish is an important animal-source food for humans. However, the oxidative stress-induced by intensive aquaculture usually causes deterioration of fish meat quality. The nutritional way has been considered to be a useful method for improving fish flesh quality. This study using the same growth experiment as our previous study was conducted to investigate whether vitamin A could improve flesh quality by enhancing antioxidative ability via Nrf2/Keap1 signaling in fish muscle. Six diets with different levels of vitamin A were fed to grass carp (Ctenopharyngodon idella) (262.02 ± 0.45 g) for 10 weeks. Dietary vitamin A significantly improved flesh sensory appeal and nutritional value, as evident by higher pH24h value, water-holding capacity, shear force, contents of protein, lipid, four indispensable amino acids (lysine, methionine, threonine, and arginine) and total polyunsaturated fatty acid in the muscle. Furthermore, dietary vitamin A reduced oxidative damage, as evident by decreased levels of muscle reactive oxygen species, malondialdehyde, and protein carbonyl, enhanced activities of antioxidative enzyme (catalase, copper/zinc superoxide dismutase (CuZnSOD), MnSOD, glutathione peroxidase, and glutathione reductase), as well as increased content of glutathione, which was probably in relation to the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. These findings demonstrated that dietary vitamin A improved flesh quality probably by enhancing antioxidant ability through Nrf2/Keap 1a signaling in fish.

Grass Carp (Ctenopharyngodon idella) KAT8 Inhibits IFN 1 Response Through Acetylating IRF3/IRF7

Post-translational modifications (PTMs), such as phosphorylation and ubiquitination, etc., have been reported to modulate the activities of IRF3 and IRF7. In this study, we found an acetyltransferase KAT8 in grass carp (CiKAT8, MW286472) that acetylated IRF3/IRF7 and then resulted in inhibition of IFN 1 response. CiKAT8 expression was up-regulated in the cells under poly I:C, B-DNA or Z-DNA stimulation as well as GCRV(strain 873) or SVCV infection. The acetyltransferase domain (MYST domain) of KAT8 promoted the acetylation of IRF3 and IRF7 through the direct interaction with them. So, the domain is essential for KAT8 function. Expectedly, KAT8 without MYST domain (KAT8-△264-487) was granularly aggregated in the nucleus and failed to down-regulate IFN 1 expression. Subcellular localization analysis showed that KAT8 protein was evenly distributed in the nucleus. In addition, we found that KAT8 inhibited the recruitment of IRF3 and IRF7 to ISRE response element. Taken together, our findings revealed that grass carp KAT8 blocked the activities of IRF3 and IRF7 by acetylating them, resulting in a low affinity interaction of ISRE response element with IRF3 and IRF7, and then inhibiting nucleic acids-induced innate immune response.

First Record of Pseudocapillaria tomentosa (Dujardin, 1845) Moravec, 1987 in Cultured Grass Carp in Basrah Province, Iraq

A total of 110 specimens of cultured grass carp Ctenopharyngodon idella (Pisces: Cyprinidae) were collected from three different fish pond stations in Basrah province, during the period from March till July 2007. Postmortem parasitological examinations indicated infection of the grass carp with the nematode Pseudocapillaria tomentosa and this infection occurred only in Faddak fish ponds during all months of investigation. The maximum incidence of infection was 26.6% in April, while the maximum intensity of infection was 8.5 in June. The present finding of this nematodes represents its first record in Iraqi fishes.

Effects of Water Temperature on Growth Criteria of Fingerlings of Grass Carp, Ctenopharyngodon idella (Valenciennes, 1884)

The current experiment was conducted in the Fish Laboratory of Aquaculture Unit, College of Agriculture, University of Basrah from 28th January to 19th April 2021. Growth criteria of grass carp Ctenopharyngodon idella were investigated using four water temperatures (15, 20, 25 and 30 oC). Grass carp fingerlings (4.92 g) were brought from earthen ponds of the Aquaculture Unit in Al-Hartha Station for Agricultural Researches, North Basrah. The results indicated that the highest final weight (7.96 g) was reached by fishes at 15 0C, while the lowest final weight (7.22 g) was at 30 0C. Weight increments for fishes were 3.02, 2.97, 2.76 and 2.22 g for water temperatures of 15, 20, 25 and 30 0C, respectively. Fishes had the highest daily growth rate (0.0425 g/day) at 15 0C and the lowest (0.0312 g/day) at 30 0C. Fishes at 20 0C had the best feed conversion rate of 4.03, while fishes at 30 0C had the worst feed conversion rate of 5.29. It can be concluded that the best growth criteria were obtained from fishes at 15 0C and 20 0C, while the worst was observed at 30 0C.

Comparison of Some Biological Parameters between Young Grass Carp, Ctenopharyngodon idella (Valenciennes, 1884) fed on Artificial Diet and Alfalfa inEarthen Ponds at Basrah, Iraq

The current study aims to compare the relationships of some biological parameters of young grass carp, Ctenopharyngodon idella (Valenciennes, 1844) fed on artificial diet and alfalfa in earthen ponds. These parameters included length-weight relationship, relative length and weight of the alimentary canal, condition factor and survival rate. Results of lengthweight relationship showed that no significant differences (P>0.05) were recorded for the t-test for the ideal value of 3 for fishes fed on artificial diet or alfalfa plant. The condition factor of young grass carp fed on artificial diet ranged between 0.021 to 1.074, while for fishes fed on alfalfa plant was 0.023 to 1.270 for allometric and Fulton’s condition factor, respectively. Also, there was no significant difference (P>0.05) for fishes fed on both diets in all biological parameters, the relative length of the alimentary canal for fishes fed on artificial diet (1.65) and on alfalfa plant (1.69), while the relative weight of the alimentary canal were 0.0285 and 0.0218 for fishes fed on both diets, respectively. Results also showed that the Zihler coefficient were 7.43 and 7.62, respectively. The survival rate was 100% for both treatments.