Screening of potential feed palatants for use in all-plant protein diets for hybrid striped bass Morone chrysops x M. saxatilis.

Previous experience in our lab has shown that all-plant protein diets are poorly accepted by hybrid striped bass.  Poor feed intake reduces animal growth and masks potential production savings that can be garnered through utilization of less expensive feed ingredients to supply essential nutrients.  Feeding stimulants, i.e., palatability enhancers or "palatants"-like amino acids, peptides, crustacean meals, or betaine-are typically used to stimulate intake when some feed formulas are not readily consumed by the animal.  Novel products have recently been introduced as palatants for pet and farm animal diets that have not been tested in several species of commercially grown fish.  The purpose of this study was to screen a variety of practical compounds as potential palatants for developing commercial plant protein diets for hybrid striped bass.

Multiple series of short, 5-day feeding trials with juvenile hybrid striped bass were conducted to assess feed intake of an all-plant diet supplemented with one or more palatants of interest.  Compounds tested included betaine (Bet or trimethylglycine), molasses, liver by-products (Simmons Proteins, Inc.), ProOmega  (BioOregon Protein, Inc.) crawfish oil, shrimp oil, poultry oil, garlic oil, inositol, inosine, , and others .  An all-plant diet formula was manufactured in a new, soft-extruded, "HMF" pellet (patent pending) developed by the USDA/ARS - Trout Grains Project (Bozeman, MT) and served as the carrier matrix for testing the various compounds of interest.  The HMF pellets are capable of being dried, frozen, and then rehydrated when needed, without losing their essential nutrient composition (i.e., low leaching) or their advantageous physical characteristics, e.g., soft, chewy, yet resilient. The HMF pellet matrix allowed us to maintain consistent composition, quality, and uniformity of diets across all test palatants.  Water soluble palatants were added to pellet rehydration water and all test diets were rehydrated to equal  moisture content.  Diets were fed to four replicate tanks twice daily, about 8h apart to apparent satiation without over feeding. Daily feed intake was determined by weighing feed containers assigned to each tank.  To assess palatant effectiveness:  weight gain, daily feed intake, and increased acceptance over time were measured for each test compound during the 5-day feeding trial and compared to tanks of fish fed positive and negative control diets that consisted of an extruded commercial hybrid striped bass diet (Rangen Inc., Angleton, Texas) and the unsupplemented, plant protein "HMF" diet.  Results will be presented at the meeting.