Joyce E. Milley

Effects of dietary cholesterol on astaxanthin transport in plasma of Atlantic salmon (Salmo salar)

The effect of dietary cholesterol on astaxanthin (Ax) absorption and transport in the plasma of Atlantic salmon was investigated. Under controlled conditions, three experimental diets, non-pigmented diet (NPD), NPD with 40 mg Ax kg(-1), and NPD with 40 mg Ax kg(-1) and 2% cholesterol, were fed to juvenile salmon reared in sea water. After 12 weeks, blood was collected and plasma separated for analysis of plasma Ax and cholesterol content. In addition, plasma samples from each group of fish were fractionated into lipoproteins using a sucrose density gradient and ultracentrifugation. The apolipoprotein components of VLDL, LDL and HDL from each sample fraction were separated using SDS-PAGE. The addition of 2% cholesterol to the Ax-containing diet significantly increased the concentration of Ax and cholesterol in fish plasma. The protein-rich fraction was found to be the major carrier of Ax in salmon plasma. Cholesterol supplementation significantly increased Ax in plasma and VLDL as well as increasing plasma cholesterol. The VLDL fraction showed the most significant change in fish fed diet supplemented with cholesterol resulting in higher levels of Ax in this lipoprotein. The results clearly show that dietary cholesterol had a significant effect on the Ax transport process in the blood.

Effect of hormone implantation on cryopreservation of Atlantic halibut (Hippoglossus hippoglossus L.) sperm

Hormone implantation is widely applied in halibut (Hippoglossus hippoglossus L.) aquaculture to extend the sperm production season of broodstock males. The ability to combine this technique with cryopreservation would increase sperm availability, thereby improving reproduction success and facilitating gene management. In this paper, the cryopreservation ability of sperm from hormone-treated males was examined at three times post-implantation and compared with that of sperm from males that were not hormone-treated. All sperm samples were cryopreserved using the same method. The effectiveness of these techniques was assessed by examining the fertilization rate and motility of thawed sperm. The spermotocrit and concentration of fresh sperm samples were measured to reveal the effect of hormone implantation on sperm characteristics. The reported results indicate that hormone implantation did not affect cryopreservation efficiency. The fertilization rate resulting from thawed sperm of hormone-treated males showed no significant difference from that of untreated males or from fresh sperm. A significant positive relationship was demonstrated between the spermatocrit and concentration of sperm; and a significant decrease of spermatocrit was found in sperm collected from hormone-treated males 14days post-implantation. No significant linear relationship between spermotocrit and fertilization rate of thawed sperm was shown.