A 3 × 2 factorial experiment was designed to evaluate the effect of different ratios of
fish meal (FM): sunflower meal (SFM) with or without exogenous xylanase supplementation
on growth, feed utilization, digestive enzymes activities, apparent digestibility,
intestinal and liver morphology and chemical composition of Nile tilapia,
Oreochromis niloticus. Three isonitrogenous (329.80 g/kg of crude protein) and isoenergetic
(18.46 MJ/kg gross energy) experimental diets were formulated as SFM1
(FM:SFM = 2:1), SFM2 (FM:SFM = 1:1) and SFM3 (FM:SFM = 1:2) based on protein
content. Each diet was supplemented with 0 or 0.5 g/kg of exogenous xylanase and
was fed to triplicate groups of twelve fish (with initial weight, 1.31 ± 0.02 g) for
84 days. After 84 days of feeding period, the highest weight gain, specific growth
rate, protein efficiency, protein productive value and the best feed conversion ratio
were recorded in fish fed either SFM1 or SFM2 supplemented with exogenous xylanase.
Whereas lowest growth performance was recorded in fish fed SFM2 and SFM3
un‐supplemented with xylanase. The highest activities of chymotrypsin, trypsin, lipase,
amylase, alkaline phosphatase and cholecystokinin were observed in fish fed
SFM1 and SFM2 diets supplemented with xylanase. The highest ADCs of dry matter,
protein, lipid and digestible energy were recorded in fish fed SFM1 and SFM2 diets
supplemented with exogenous xylanase. Supplementation of exogenous xylanase
improved muscularis mucosa thickness, height of mucosal folds and enterocytes of
intestinal fish. Addition of exogenous xylanase increased the calcium and phosphorus
retention. Results of this study indicated that the addition of exogenous xylanase
to diet containing high inclusion level of sunflower meal improved growth, digestive
enzymes, nutrient digestibility, histological morphometric of liver and intestine and
nutrient retention. |
