The US imports approximately 75% of domestically consumed seafood, so increasing seafood
production through aquaculture is critical for reducing this deficit. Expanding aquaculture depends in part on efficient broodstock management, including appropriate broodstock nutrition. Maternal nutrition can affect growth in the next generation through inherited epigenetic modifications like DNA and histone methylations that persist in the offspring. Therefore, identifying broodstock nutritional strategies that exploit these mechanisms and improve offspring growth performance will increase production capacity. Here we combine genetic selection and nutri-epigenetics to improve performance.
Recently, we demonstrated that maternal dietary supplementation with choline and methionine in fillet-yield selected lines results in increase growth performance in offspring beginning at 360 days post hatch. To better understand the interaction between maternal nutrition and genetic selection on offspring performance we focused on the role of maternal choline intake on trout currently used within the industry – disease resistance selected rainbow trout. Since 2005, the National Center for Cool and Cold Water Aquaculture has maintained, within the odd-year NCCCWA breeding program, 5 disease-resistance selected lines: 1) resistance to Flavobacterium psychrophilum (Fp-R), 2) resistance to F. psychrophilum and F. columnaris (Fp/Fc-R), 3) randomly mated controls (Fp-C), 4 and 5) two susceptible lines (Fp-S and Fc-S). For this work, the disease-resistant selected lines were utilized. Our objectives were to 1) identify how choline levels in rainbow trout broodstock diets affect growth and fillet yield in the next generation and 2) characterize how the choline concentration in the rainbow trout egg affects fry performance. Within each objective, treatment effects on the epigenome and transcriptome were analyzed to characterize mechanisms that respond to choline and establish links between epigenetic modifications in the genome and the phenotype of the offspring.
Interestingly, within the disease-resistant selected trout, maternal dietary intake of choline had no effect on offspring growth performance, which disagrees with previous data in fillet-yield selected trout lines maintained by NCCCWA where offspring growth was increased after 360 days post hatch. However, global gene expression (RNAseq) and global methylation (RRBS) analyses demonstrate that maternal dietary choline intake affects key metabolic, stress, and hypoxia-related pathways. These data indicate that stress and hypoxia tolerance are likely performance outcomes positively affected in offspring by maternal choline intake.