Analysis of the optimum krill oil supplementation strategy for ovarian high-quality development in the female Redclaw crayfish, Cherax quadricarinatus

Krill oil, as a high-quality source of phospholipids, has been shown to positively influence the gonadal development of aquatic animals. Five isonitrogenous and isolipidic diets with krill oil (KO) supplementation at 0 % (Ctrl), 1 %, 2 %, 3 %, and 4 % were formulated. A 10-week nutritional enhancement trial was conducted to assess the effects on ovarian development in female Cherax quadricarinatus broodstock. The result indicated that linear and quadratic increase of hepatosomatic index and gonadosomatic index by increasing KO level, and reached the peaks at 3 %. Female crayfish fed the diet with 3 % KO significantly enhanced antioxidative capacity, steroid hormone synthesis, as well as vitellogenin synthesis and transport. Based on ovarian histology and vitellogenin analysis, the results indicated that dietary 3 % KO supplementation accelerated yolk granule deposition and promoted oocyte maturation. Additionally, 3 % KO supplementation promoted lipid deposition and mobilization efficiency of triglyceride between hepatopancreas to the ovary. From serum metabolomics, a large number of phosphatidylcholine and phosphatidylethanolamine with different fatty acids were detected, which indicated vital role in ovarian maturation. The metabolism of glycerophospholipids, glycine, serine, threonine, and arachidonic acid was significantly upregulated in the 3 % KO group. Notably, the relative contents of prostaglandin E2, prostaglandin B2, and prostaglandin A2 were significantly increased. Prostaglandins are closely related to hormone secretion, yolk deposition, lipid metabolism, and antioxidant capacity, showing particularly strong correlations with estradiol, progesterone, molt-inhibiting hormone, gonad-inhibiting hormone, and ovarian vitellogenin receptor. In conclusion, adding 2.82–3.20 % krill oil to the feed promotes the healthy development of female C. quadricarinatus ovaries. This study highlights the potential of krill oil as a high-quality phospholipid source for optimizing broodstock nutrition and enhancing reproductive performance in crustacean aquaculture. • Krill oil is a high-quality source of phospholipids and optimizes broodstock diets. • Krill oil enhances lipid deposition, mobilization, antioxidant capacity, and steroidogenesis. • Krill oil (2.82 %-3.20 %) significantly enhances ovarian maturation in C. quadricarinatus .