Pelleted Dry Rations for Trout Propagation in Michigan Hatcheries

Abstract

Diets of pelleted animal and vegetable meals were compared with dry-meal and chopped raw-meat diets as food of rainbow and brook trout. Evaluation was made by bimonthly measurement of weight and length, daily mortality, and physiological changes. Pelleted dry-meal diets were not accepted immediately as food by rainbow and brook trout. This was evidenced by a loss of weight during the first two weeks of feeding pelleted food. Lost weight was regained after four weeks of feeding. All dry-meal ingredients pelleted in the combinations used were acceptable as trout food when supplemented with raw beef liver at least one day every three weeks. Dry diets resulted in no reduction of growth rates when fed at one-half to five-eighths the amounts recommended for raw-meat mixtures. A diet containing brewers yeast produced a greater gain in weight of rainbow trout than an otherwise identical diet containing torula yeast. Also, it was found that a pelleted diet was superior to a raw beef liver diet. The adoption of dry pelleted diets as standard rations by all state fish hatcheries in Michigan increased trout production in pounds by 60 percent and reduced fish food expenditures by 40 percent.