Dietary microbial phytase supplementation and utilization of phosphorus, trace minerals and protein by rainbow trout (Oncorhynchus mykiss (Walbaum) fed soybean meal diets.

The effects of heat and enzyme treatments of soybean meal on apparent digestibility of total phosphorus, phytate phosphorus, protein, ash, calcium, magnesium, copper, iron, manganese, strontium and zinc were examined in trout. Absorption of the test nutrients was estimated using yttrium as an non-absorbable indicator. The heat processing treatments (dry roasting, microwaving, steam heating and cooking) has no measurable effect on the apparent absorption of phosphorus or other minerals. Phytase supplementation increased the apparent absorption of crude protein and the various minerals in low-ash diets containing soybean meal, but had little effect on the high-ash diets containing both soybean and fish meal. The apparent digestibility of phosphorus increased with the level of the phytase in the diet. Excretion in the feces of fish fed a low-ash diet containing phytase-treated soybean meal was 0.32grams per kilogram of diet consumed, or a 95-98% reduction compared with phosphorus excreted by fish consuming commercial trout feeds.

Sugiura, S.H. and co-workers. 2001. Dietary microbial phytase supplementation and utilization of phosphorus, trace minerals and protein by rainbow trout (Oncorhynchus mykiss (Walbaum) fed soybean meal diets. Aquaculture Research 32(7):583-592).