Wallace JL, Murray F & Little DC (2016) Effects of b-xylanase and 6-phytase on digestibility, trace mineral utilisation and growth in juvenile red tilapia, Oreochromis niloticus (Linnaeus, 1758) x O. mossambicus (Peters, 1852), fed declining fishmeal diets. Journal of Applied Ichthyology, 32 (3), pp. 471-479. https://doi.org/10.1111/jai.13055
In response to the global sustainability drive to lower fishmeal (FM) inclusion in aquatic feeds, exogenous enzymes can improve nutrient digestibility in monogastric plant-based diets. A 80-day experiment was conducted to evaluate the combined effects of xylanase and phytase on digestibility, trace mineral utilisation and growth in juvenile red tilapia, Oreochromis niloticus x O.mossambicus, (48.8 g±13.9;μ ± STD) fed declining FM diets. Basal diets were formulated to contain 0, 3 and 5% FM with and without xylanase (0.385 g kg−1) and phytase (0.075 g kg−1), forming six treatments. Each treatment was randomly assigned to four replicates, 20 fish tank−1; mean water temperature 28.98 ± 0.73°C. Although the size of the effects was modest, growth performances (feed intake, FCR, growth rate) decreased with lower FM levels (P<0.05) but improved with enzyme supplementation. Enzyme supplementation increased P digestibility and trace mineral uptake (P<0.05), but no effects were seen on protein digestibility and N retention. Nevertheless, tilapia fed the enzyme-supplemented 3% FM and control 5% FM diets performed comparably (P<0.05). This potentially justifies a 2% FM reduction for tilapia diets using exogenous xylanase and phytase without significant effects on digestibility, trace mineral utilisation and growth.
Journal of Applied Ichthyology: Volume 32, Issue 3