Evaluation of the nutritional quality of co-products from the nut industry, algae and an invertebrate meal for rainbow trout, Oncorhynchus mykiss.

Authors: Barrows, Frederic; Frost, Jason

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2014
Publication Date: 9/3/2014
Citation: Barrows, F., Frost, J.B. 2014. Evaluation of the nutritional quality of co-products from the nut industry, algae and an invertebrate meal for rainbow trout, Oncorhynchus mykiss. Aquaculture. 434:315-324.

Interpretive Summary: The static supply and increasing demand for fish meal has created a need to evaluate a variety of alternate proteins. Many species of algae are being grown for as a potential source of bio-fuels, and mussel meal is thought to increase feed intake. The tree nut industry is based primarily on whole nuts with production totaling ~1,081,000 tons in California during 2010. A portion of this production is broken or chipped and has low value non-human uses. A method was developed to modify the nutritional profile of this material to fit specifications for aquaculture feeds. Three feeding studies were conducted, and performance of fish in the first study eliminated the algae and muscle meal from the evaluation. As in the first study, the next two studies demonstrated that nut meals are highly palatable, digestible, and able to support high levels of growth whether replacing fish meal or soy protein concentrate in the diet of rainbow trout.

Technical Abstract: The static supply and increasing demand for fish meal has created a need to evaluate a variety of alternate proteins. Many species of algae are being grown for as a potential source of bio-fuels, and mussel meal is thought to increase feed intake. The tree nut industry is based primarily on whole nuts with production totaling ~1,081,000 tons in California during 2010. A portion of this production is broken or chipped and has low value non-human uses. A method was developed to modify the nutritional profile of this material to fit specifications for aquaculture feeds. Evaluation of ingredient included testing with three life stages of rainbow trout. A fry screening study was conducted to determine which ingredients would be evaluated in digestibility and growth studies. First feeding trout fed a diet containing 5% fish meal and 49-58% of the nut meals had survival and growth that was similar to trout fed a diet with 55% fish meal during a six week screening study. The trout fed the algae’s and the mussel meal diets grew slower and were dropped from further evaluation. Both pistachio and almond meals had apparent digestibility coefficients for crude protein, lipid, and amino acids similar to fish meal. Trout with an average initial weight of 20 g/f were fed one of ten experimental diets for 12 weeks. There were two series of diets, where protein from fish meal was either 50% or 100% replaced with each of the nut meals, or the protein from soy protein concentrate (SPC) was replaced with the nut meals. The trout fed the nut meals in the fish meal series all had weight gains equivalent to trout fed the fish meal control (753%) except the trout fed the partial replacement with almond meal (614%). Analysis of the feed showed much lower lipid levels than expected, ~12% versus 18% total crude lipid, which could explain the lower gain. Trout gained between 600 and 900% of their initial weight. When SPC was replaced with the nut meals, growth of the fish fed the SPC was the same as fish fed the nut meals (648%) except for the fish fed the complete replacement with pistachio meal which had a greater gain of 830%. These three studies demonstrate nut meals to be highly palatable, digestible, and able to support high levels of growth whether replacing fish meal or soy protein concentrate.