The impact of post-ovulatory ageing on the development of diploid and Atlantic salmon salar

This study is the first to investigate the effects of post-ovulatory ageing (POA) on both diploid and triploid Atlantic salmon (Salmo salar L.). Following ovulation, female broodstock were partially stripped periodically (at 0, 5, 10, 15 and 20 days post-ovulation, DPO), creating five groups of ova with differing durations held in the body cavity. Survival and bone architecture were negatively impacted by increasing POA, irrespective of ploidy, and an increase in individual growth variation was observed, particularly in triploids. Several ovarian fluid and egg quality parameters were screened to determine potential prospective biomarkers that may predict the future success of an egg batch. Ovarian fluid osmolality and egg lipid composition, vitamin E concentration and TBARS emerged as good candidates. Furthermore, significant changes in abundance of 19 proteins involved in cell organisation, metabolism and reproduction were observed at different stages of POA. Also, a suite of genes involved in energy metabolism, apoptosis and cell cycle regulation showed significantly reduced expression in eggs at 20 DPO compared to 0 DPO. The data show that increasing POA negatively impacts egg survival and future growth and increases deformity prevalence. Several potential biomarkers show promise and should be investigated further. Although egg quality appears to remain stable up to 10 DPO, the data suggests that fertilising eggs within 5 DPO would reduce the variation in growth, thus improving future performance potential and further benefitting stock management of both diploid and triploid Atlantic salmon.