Abstract:

Ten different plant protein and/or starch sources were studied in a 5-week experiment with triplicate groups of 0.7-kg Atlantic
salmon in seawater, pre-adapted to a diet with fish meal, faba beans, sunflower cake, and wheat gluten as sources of protein and
starch. The experimental ingredients were corn gluten, defatted soybean, defatted sunflower, dehulled lupin, defatted double-low
rapeseed, whole field pea, whole and dehulled faba bean, whole wheat and naked oat, tested one at a time (14–24% inclusion). The
diets were balanced by addition of pure wheat starch and/or pure cellulose, to obtain equal macro nutrient compositions. The
control diet consisted of fish meal, wheat starch, cellulose and fish oil. The results showed reduced faecal dry matter content in fish
fed the soybean diet and to a lesser extent in those fed the sunflower, lupin and rapeseed diets. Diets containing lupin and rapeseed
resulted in a moderate increase in the viscosity of the digesta, while diets with wheat and oat increased viscosity of digesta more.
Apparent digestibility of lipid decreased linearly with increasing dietary cellulose level. A significant reduction in the digestibility
of crude protein was seen for the soybean, sunflower, rapeseed and oat diets, reflecting reduced digestibilities of most amino acids.
The salmon fed the corn gluten, lupin, pea, bean and wheat diets had protein digestibilities comparable to the control group. The
digestibility of phosphorus was highest for salmon fed the rapeseed diet and lowest for fish fed the oat diet. Faecal excretion of
sodium was highly elevated for salmon fed the soybean diet, and moderately elevated for fish fed the corn gluten and sunflower
diets. Faecal excretion of zinc was elevated in the fish fed the oat diet. None of these observations were significantly related to the
dietary concentration of phytic acid. A histological examination of the stomach, mid- and distal intestine of all groups showed no
other irregularities than enteritis in the distal intestine of salmon fed soybean meal. The present study demonstrated a potential for
several plant ingredients, such as field pea and faba bean, partly replacing high-quality fish meal in diets for Atlantic salmon, based
on nutrient digestibilities and absence of pathologies in the stomach and intestine