Dalsgaard et al. (2012) did an additional studywith rainbowtrout in
which independent diets with high inclusion levels of three different
plant-based feedstuffs (soybean [344 g kg−1], sunflower [246 g kg−1]
and rapeseed [264 g kg−1]) meals were supplemented with three different
enzymes (β-glucanase [67 mg kg−1], xylanase [208 mg kg−1]
and protease [228 mg kg−1]) and apparent nutrient digestibility was
assessed. Enzyme supplementation had onlymoderate effects on apparent
nutrient digestibility in the sunflower and rapeseed experiments,
while β-glucanase and protease improved the apparent digestibility of
all nutrients in the soybean experiment. The effect was more pronounced
for lipids than for other nutrients. β-Glucanase had a positive
effect on energy retention of the fish in the soybean experiment, while
there were no effects on nitrogen retention or fish performance in any
of the three experiments. This was the third study in which no effects
of carbohydrase enzyme supplementation on rainbow trout growth
performance were observed (Farhangi and Carter, 2007; Ogunkoya
et al., 2006); although, in the case of this study, the feeding trial only
lasted 19 days.