Mineral availability from barley low phytic acid grains in rainbow trout (Oncorhynchus mykiss ) diets

Abstract

Phosphorus storage within plant seeds occurs mainly as phytic acid, which has profound implications on the use of seeds as food material. Phytic acid phosphorus is unavailable to non‐ruminants, leaches ionic minerals during digestion, and is excreted at elevated levels as a waste product. This presents a problem in nonruminant livestock production including current efforts to develop renewable grain and legume products for use in fish feeds. The development of lines of several cereal grain species that have reduced seed phytic acid concentration provides a novel approach to dietary and environmental problems associated with seed phytic acid. Utilizing four isogenic strains of barley (one normal for seed phytic acid, and three low phytic acid lines that produce seeds with approximately 50, 70 and 95% reductions in phytic acid) the apparent digestibility of nutrients in formulated diets containing these barleys at a level of 30% was measured using rainbow trout (Oncorhynchus mykiss). Also examined was the apparent availability of several minerals including phytate phosphorus and total phosphorus. Results from these studies corresponded well with the results of other animal studies that evaluated low phytic acid cereal grains. With increasing reductions in seed phytic acid, seed available phosphorus increased and faecal phosphorus was reduced by up to 50%. Calcium availability increased, copper and sulphur decreased, and the other tested minerals demonstrated either increased or decreased availability in a manner uncorrelated to grain phytic acid concentration.

Effects of Four Independent Low‐Phytate Mutations on Barley Agronomic Performance

“…Previous characterizations of the original mutant lines, using seed produced in two different environments, Aberdeen, ID, and Saskatoon, SK, Canada, (Dorsch et al, 2003;Leytem et al, 2004;Overturf et al, 2003;Thacker et al, 2003), showed similar results with respect to the alterations in phosphorus profiles conditioned by these four mutations. Previous characterizations of the original mutant lines, using seed produced in two different environments, Aberdeen, ID, and Saskatoon, SK, Canada, (Dorsch et al, 2003;Leytem et al, 2004;Overturf et al, 2003;Thacker et al, 2003), showed similar results with respect to the alterations in phosphorus profiles conditioned by these four mutations.…”

The effect of postprandial changes in pH along the gastrointestinal tract on the distribution of ions between the solid and fluid phases of chyme in rainbow trout

“…To counteract these effects and increase dietary mineral assimilation, several approaches are being attempted. Low phytic acid grains are being developed, which when fed to rainbow trout increased Ca 2+ availability by 2–4 fold compared with control phytic acid diets (Overturf et al. 2003).…”

Replacing fishmeal and fish oil in industrial aquafeeds for carnivorous fish

“…This increases potential combinations of feedstuffs to include in aquafeeds, as they may complement one another to provide a balanced dietary EAA profile. Breeding new plant varieties with better amino acid (AA) profiles or low phytic acid is also a strategy for improving plant utilization in aquafeeds (Gatlin et al, 2007;Overturf et al, 2003). These recommendations seem, however, very conservative, particularly for lysine, for which the dietary allowance and estimated requirement values are, respectively, 6.2% and 5.0% of dietary protein.…”