Effects of β‐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 |
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| Authors: | J L Wallace F J Murray D C Little |
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| Affiliation: | Institute of Aquaculture, University of Stirling, Scotland, UK |
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| Abstract: | 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. |
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