Currently there is a lack of information on the most efficient grow out diets for juvenile white sturgeon from 1 year to 3-5 years, when sexing can occur. Most studies have focused on sturgeon below 1 year and over 7 years of age. During growout, producers maintain excess fish inventories and feed at high rates to maintain rapid growth. A majority of the feed costs incurred by producers occur in this growout period before sexing. Identifying the optimal diet for growout could allow for a significant reduction in feed costs for producers in the Western U.S. The study objective was to determine which of the experimental diets provided a 90% optimum response in terms of growth parameters.
A 20-week feed trial was conducted using 1.5-year-old juvenile white sturgeon, with a mean weight of 1105 ± 11.57 g. 14 fish were randomly assigned to each of the 24 400L tanks used. The flow rates were 3.0 L min-1, water temperature was 16 OC, and a natural photoperiod was maintained to mimic commercial culture conditions in the Hagerman Valley. The sturgeon were fed at 0.7% of their body weight per day. At the onset of the study and at weeks 8, 14, and 20 the sturgeon from each tank were bulk weighed. Utilizing a simplex mixture design model with a constrained region, 14 experimental diets were formulated. The constrained region was defined using the known requirements of macronutrients for white sturgeon. The macronutrients in the diets ranged from 45-65%, 10-30%, 13.67-37.84% for fishmeal, fish oil, and wheat starch, respectively on a dry matter basis.
The data gathered suggested that the ideal diet with an optimum response of 90% would have a blend ratio of 0.6559 FM, 0.1884 FO, and 0.1556 WS. With this ratio the predicted SGR, DGI, and TGC are 0.33 %/day, 1.25 g1/3/day, and 0.07 g1/3/degree day, respectively. The FCR is predicted to be approximately 1.62 while the mean weight gain is expected to be 37.73%. This predicted blend will have an approximate survival rate of 96.62%.