Effects of arachidonic acid (ARA) on reproduction, immunity, and lipid metabolism of Penaeus vannamei broodstocks

Pacific white shrimp (Penaeus vannamei) is a staple in aquaculture due to its rapid growth cycle, adaptability to both freshwater and saltwater, broad temperature tolerance, minimal nutritional needs, and high meat yield. It is recognized the Chinese shrimp (P. chinensis) and black tiger shrimp (P. monodon), as one of the three most important shrimp species for global aquaculture. The industry's sustainable growth hinges on the development of superior feed, breeding of high-quality stocks, and the provision of premium seedlings to enhance the reproductive performance and quality of the Pacific white shrimp's offspring. The research investigates the impact of arachidonic acid (ARA) on the reproduction, immunity, and lipid metabolism of the Pacific white shrimp's broodstock, offering insights for selective breeding and feed formulation. Males at six months of age and unilaterally eyestalk-ablated female shrimps were selected to reflect actual breeding practices. They were randomly assigned to five groups, with females and males reared separately. The groups were fed with different levels of ARA (0.03%, 2.70%, 4.99%, 10.63%) in pelleted feed (designated as Z1-Z4) and a control group with natural feed (clam worms) (designated as Z5). Findings indicate that the weight gain rate (WG) of female shrimps on the pelleted feed was significantly superior to the control. The hepatopancreatic index (HSI) of the broodstock showed an initial increase followed by a decrease with escalating ARA concentrations. At an ARA concentration 4.99%, optimal hepatopancreatic development, peak hatching rate, and superior larval yield and quality were observed, along with heightened expression of genes pivotal to ovarian development (Vtg, VtgR, VASA, and FAMeT2). This ARA level also modulated lipid metabolism in the female hepatopancreas, enhancing the expression of genes associated with lipid processing and transport (PL, SREBP and FATB), thereby influencing the fatty acid profile of fertilized eggs. Notably, it elevated the functional fatty acid DHA content and adjusted the ratios of ∑n-3 and ∑n-6 polyunsaturated fatty acids (PUFA). Due to the antagonistic relationship between reproduction and immunity, this ARA concentration led to a reduction in oxidant stress and non-specific immune responses. In conclusion, different ARA levels in feed significantly influence the growth, reproductive success, immune function, and lipid metabolism of the Pacific white shrimp's broodstock. To prioritize reproductive performance, an ARA content of 4.99% in the broodstock feed is recommended for its positive effects on ovary development and larval production, offering valuable guidance for the ARA application during the breeding phase of the Pacific white shrimp.