Endurance tests in “The Flume”
To test the influence of feed on cardiovascular capacity and simultaneously examine the role of phospholipids, four test diets were used.
- Two contained high levels of EPA and DHA, and two had low levels.
- One of the levels contained krill oil – a source of fatty acids – and the other fish oil.
- The feed was administered over a period of 8 weeks before samples were taken and measurement of cardiac performance was made in "The Flume".
Both groups receiving feed containing EPA and DHA from phospholipids (PLL and PLH) had thicker heart walls than those in the groups who received fish oil-based feed. This was despite the fact that both diets contained identical levels of EPA and DHA.
The group that had low levels of EPA and DHA (PLL) also had thicker heart walls than the group that had received high levels of EPA and DHA in the form of fish oil (TGH).
A thicker heart wall can be crucial to the robustness of the fish in circumstances where the heart is under stress for various reasons.
The illustration shows where measurements of the heart wall were carried out. Photo: Anthony P. Farrell
The table shows the distances (in body lengths) that the fish swam in “The Flume” before they were exhausted. The fish had been fed on low levels of EPA + DHA from fish oil or krill meal.
There was a tendency for the krill group to swim further before becoming exhausted.