Improving High Soy Feed Formulations Supplemented with Taurine in U.S. Marine Fish Feeds
The Florida pompano is one of several species of jacks that are considered highly prized food fish. They have a flakey texture and a mild flavor. Currently, they are reared in intensive indoor systems and outdoor cages in many areas of the world. Based on ongoing research this species performs well on soy based diets as long as nutritional and palatability needs are met. Previous USB funded projects have systematically evaluated nutrient restrictions that limit the inclusion of soy products in the feed. To date, we have been very successful in increasing the level of soy protein (solvent extracted meal and soy protein concentrate) in practical feed formulations for this species.
Further research efforts have been supported and coordinated with a range of funding agencies to allow leveraging of research dollars. Previous studies have included the use of poultry byproduct meal and meat and bone meals as alternatives to fish meal in soy based diets. This research confirmed methionine and lysine were not deficient in high soy diets (~50% diet) but there was a clear response to taurine. The physiological characterization of deficiencies and the dietary requirement for taurine are currently underway. It is clear taurine is a limiting nutrient, even with supplements for lysine, methionine and taurine (as required), the removal of animal protein and/or fish meal results in depressed growth. This indicates that another nutrient is limiting in high soy diets when animal protein is reduced.
As part of this research we re-evaluated the amino acid profile of recent feed formulations to identify if there is a consistent amino acid or group of amino acids that are reduced. In the most recent diets glycine, valine and histidine were reduced as diets were shifted. These are not typically considered essential but all function as attractants. Consequently, evaluation of these or other possibly limiting amino acids is warranted.
Another way to improve production is through proper feed management. Without proper feed management economic returns from the feed may not be optimized. A preliminary study comparing one feeding to four feedings per day resulted in almost twice the final weight of the fish. This may be due to the feeding habits of pompano which grazes in the surf zone on small bivalves and other animals. Consequently the fish has evolved to have a relatively small stomach and quick digestive systems which may mean multiple feedings are required to obtain best performance. Hence, in order to help commercial producers improve growth rates and have efficient food conversion another component of this work was to evaluate increasing the number of feedings per day to determine if feed intake and growth are affected. The objectives of this study were to: 1) evaluate if amino acids other than lysine, methionine and taurine are limiting in high soy diets with low levels of animal protein; and 2) determine the response of juvenile pompano to increasing numbers of feedings.