Experiments were undertaken to evaluate a sustained release recombinant bovine growth
hormone (rbGH) formulation (Posilac@) in salmon. The investigation was divided into two parts.
The first series of studies was used to establish optimal dosages and clearance rates for the
exogenous protein in size-selected coho salmon, and to examine the effect of rbGH treatment upon
smoltification. The second series of studies attempted to mimic the production setting, where
chinook salmon were randomly selected from a stock of animals, and taken through smoltification
to grow-out. In the first experiment, coho salmon were provided with a single injection of one of
three doses (420, 1260, 4200 pg/g body weight equivalent) of the rbGH preparation (n 2
3O/group), or were injected with a saline solution containing the high dose equivalent of rbGH.
Controls were treated with BSA, given one of three (10, 30 or 100 ~1) placebo carrier
preparations without rbGH, or left untreated. Animals receiving rbGH by sustained-release
expressed highly significant (P < 0.01) growth acceleration over a 20-week period of observation,
when compared with the five control treatments. There were no significant differences in growth