Summary
Fish silage was made from ground, whole Pacific whiting by using 2% sulfuric acid and 0.75% propionic acid by weight as the acidulent. After 3, 6, and 20 days, silage was removed, neutralized with calcium hydroxide, and drum-dried. Two additional silage products were made from unneutralized 20-day silage and silage neutralized with sodium hydroxide. Vacuum-dried Pacific whiting meal was used in the control diet. Dry pelleted diets were made using the Abernathy diet formulation s8-1, modified by replacing the fish meal with either drum-dried silage or vacuum-dried Pacific whiting meal.
After 12 weeks, no significant differences were observed in growth or feed conversion between rainbow trout fed either the control diet or diets containing 3- or 6-day-old silage. Growth and feed conversion were significantly affected by feeding diets containing silage that had been allowed to hydrolyze for 20 days. No differences in growth were observed between groups of trout fed diets containing 20-day unneutralized silage, or silage neutralized with calcium hydroxide or sodium hydroxide. Acidification of the control diet significantly affected growth and feed conversion. Neutralization of the acidified control diet with calcium hydroxide restored growth and feed conversion.
