Nut-based feed meets trout's protein needs

Young rainbow trout fed nut meal performed as well as those fed fish meal.

Researchers at the U.S. Department of Agriculture have developed a new feed ingredient made from tree nuts that is now available to fish farmers.

In an effort to develop ingredients high enough in protein for use as aquaculture feed, scientists at USDA's Agricultural Research Service (ARS) Small Grains & Potato Germplasm Research Unit in Aberdeen, Ida., worked with Adaptive Bio-Resources LLC to evaluate nuts as an alternative to fish meal.

ARS fish physiologist Rick Barrows examined methods to modify the nutritional composition in order to increase the protein content of a nut mixture made from pistachios and almonds that did not meet consumer standards for color, size and other qualities.

Barrows and his colleagues evaluated the nut mixture in separate studies. They found that young rainbow trout fed nut meal performed as well as those fed fish meal. Trout fed a diet containing 5% fish meal and 49-58% nut meal had survival and growth rates similar to those of trout fed a diet containing 55% fish meal.

The results showed that the nut meal is highly digestible, palatable and supports high growth rates in rainbow trout.

Fish fed the nut diet grew very quickly, according to Barrows. Trout fed nut meal in the study all had weight gains equivalent to trout fed fish meal, except when the nut meal contained only almonds instead of almonds and pistachios.

Read more about this research in the October 2016 issue of "AgResearch" online.

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