This study evaluated the combined effects of different dietary starch:protein ratios (SPR) and short cycles of fasting/refeeding (FR) on Nile tilapia juveniles on growth, feed and nutrient use, whole‐body composition and liver health. Three diets with SPR classified as high (S30:P32; 0.96 g:g), intermediate (S25:P36; 0.69 g:g) and low (S21:P39; 0.53 g:g) were fed to fish over 60 days on three feeding regimes: 0FR—fish fed daily (control treatment); 1 FR—fish fasted for one day and refed for three days and 2 FR—fish fasted for two days and refed for three days. Fish (2.25 ± 0.01 g) were allotted to a completely randomized factorial design (3 × 3; n = 3). Fish growth and feed conversion ratio decreased (p < .05) with increasing FR. There was no significant difference in daily feed intake between regular‐fed and fasted tilapia as a consequence of hyperphagia in fasted fish. Protein and energy productive values increased (p < .05) with increasing SPR. The occurrence of hepatic steatosis was similar (p > .05) among daily‐fed fish regardless of SPR but increased (p < .05) with increasing SPR in fasted fish. Regardless of dietary SPR, short cycles of fasting/refeeding do not promote compensatory growth. Therefore, Nile tilapia around 2g should be fed daily with low‐SPR diet.
The objective of this research was to evaluate the effect of increasing levels of associated glutamine and glutamic acid on growth performance and intestinal development of Nile tilapia, Oreochromis niloticus, fingerlings. Five isoproteic (~344.70 g kg −1 crude protein) and isocaloric diets (~3,925 kcal kg −1 gross energy) were developed containing 0, 5, 10, 15, or 20 g kg −1 of associated glutamine and glutamic acid in extruded diets. Fish (n = 2,000, mean body weight of 2.12±0.53 g) were distributed into twenty 1-m 3 floating net cages in an entirely randomized design with five treatments and four replicates, and each replicate comprised one floating net cage with 100 fish. Fish were hand-fed seven days per week, three times a day until apparent satiety for 45 days. There was a quadratic effect on final body weight, body weight gain, daily weight gain, feed conversion ratio, protein retention efficiency, net protein utilization, and intestinal villi height with optimized values for supplementation of associated glutamine and glutamic acid at 10.
This study aimed to evaluate the effects of supplemental phytase with xylanase and β‐glucanase blend on the apparent digestibility coefficient (ADC) of gross energy and nutrients, including amino acids, minerals, and nitrogen (N) and phosphorus (P) balance in Nile tilapia, Oreochromis niloticus. Diets were elaborated either without enzyme supplementation (control) or supplemented with phytase (PHY), xylanase and β‐glucanase (XB) blend or a combination of phytase plus xylanase and β‐glucanase (PHY+XB) blend. Fish (n = 192; 60 ± 3.4 g) were fed with the experimental diets replicated four times. Compared with the control group, fish‐fed with the PHY+XB diet showed a higher ADC of gross energy and nutrients, including amino acids and minerals. Also, compared to control diet, digestible energy, digestible protein and available P contents were higher in fish‐fed diet PHY+XB by 1.63 MJ kg−1, 7.21 and 4.70 g kg−1 diet respectively. Compared to the control group, fish‐fed diet PHY+XB displayed lower total N and P loss of 17.51 and 10.09 g kg−1 of body weight gain (BWG) respectively. The study findings provided new insight into the nutritive value and ecofriendliness/sustainability of diets associated with exogenous enzymes for tilapia culture.
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