experiments under natural conditions- randomisation, experimetal units (N)

Question

Hello,

I have question regarding to a research paper. In this reseach paper they test whether the probiotic supplementation to the diet affects the growth performance and immune responses of juvenile trout.

The experiment was conducted using two 500-m3 floating net cages under natural conditions in a commercial trout farm. Each cage was stocked with 30 thousand rainbow trout, in which a randomly collected sub-population of 5% of fish in each cage were individually marked with visible implant tags for growth measurements. For sampling all tagged fish were weighted before the start of the feeding trial (week 0), and then 400 tagged fish were weighted at 2, 4, 6 and 9 weeks after the start of the feeding trial for the calculation of growth per- formance parameters. Tissues were collected from 12 additional fish per treatment at the beginning and at the end of the feeding trial to assess selected non-specific immune parameters in plasma.

According to these study design information could anyone please help me to find answers for 1) is treatment and control ratio 1:1 ?, 2) how about randomisation? if you could mention that randomisation was made for growth performance and immune responses experiements, and finally 3) what is the experiemental unit for growth performance and for immune responses experiment?

I would be really grateful for your reply. Thank you!

Answer 1

1) Yes both the treatment and control nets contained the same number and biotags.

2) The point of randomization is that we don't try and favor or put bias on any one part. Since nothing was told, I would assume that this is a completely randomized trial.

3) Growth performance would be simply weight put on. As for immune response, you would have to check methods and materials, because I'm not an ichthyologist and you didn't have that part listed.