Rainbow trout, a salmonid species has an economic importance worldwide and contributes to the indigenous food security. The present study was conducted in complete randomized design (CRD) to evaluate the dietary inclusion of citric acid with phytase as supplement on growth responses of rainbow trout. There were four treatments of diets with 0.5% citric acid (T1), 1% citric acid (T2), 1.5% citric acid (T3) and 0% control (T4) of citric acid incorporated with 1200FYT phytase as supplement. The treatments were replicated three times. Total harvest weight of fish in T3 (5720.2±105.6g) was significantly higher and different than T2 (4595.9±434.9g), T1 (4589.8±240.2g) and T4 (4567.5±217.3g). The highest daily growth rate was seen in treatment T3 (1.1±0.0) which was significantly different than T2 (0.9±0.0), T1 (0.9±0.0) and T4 (0.8±0.0). The highest specific growth rate was seen in the treatment T3 (0.8±0.01) which was significantly different than T1 (0.7±0.0), T2 (0.7±0.1) and T4 (0.7±0.0). The lowest food conversion ratio was seen in T3 (2.2±0.1) which was significantly different with T2 (2.6±0.1), T1 (2.7±0.1) and T4 (2.8±0.1). Similarly, the highest protein efficiency ratio was seen in treatment T3 (1.0±0.1) which was not significantly different with T2 (0.8±0.0) and T1 (0.8±0.1) but was significantly different than T4 (0.7±0.0). No significant changes were observed in water temperature, dissolve oxygen and pH under different treatments. The present findings demonstrated that dietary inclusion of citric acid with phytase as supplement enhance growth by reducing the pH in the gut which increases the phytate hydrolysis, kills the pathogens, decreases the rate of gastric emptying, improves mineralization and nutrient absorption.

An 8-week experiment was conducted to study the effect of added Natuphos® 5000 phytase in corn–soybean meal-based diets on laying hens fed different levels of crude protein (CP) (14 and 17%). Two levels of phytase enzyme were used: 0 and 600 Phytase Units (FTU)/kg feed. The experiment used 144 Hisex Brown laying hens in a 2 × 2 factorial design. Four treatments and three replicates per treatment with 12 hens per replicate were used. Egg production was recorded daily while egg weight was assessed on 13th and 14th day of each two-week period to calculate total egg mass. Total excreta were collected and approximately 10% of the amount was used for analysis after drying in a forced draft oven. The results showed no significant effect of added phytase on excreta Calcium (Ca) content, but significantly lower Magnesium (Mg) content was observed with phytase (3.54, 2.48, 3.13 and 2.75 % for hens fed 14% CP no phytase, 14% CP + phytase, 17% CP no phytase, and 17% CP + phytase, respectively). Added phytase also significantly decreased Mg excretion measured as grams/kg of egg mass (21.43, 12.47, 16.76 and 14.75 g/kg egg mass for hens of respective dietary treatments. Phytase had a strong effect on Zink (Zn) levels with 438.96, 369.17, 434.38 and 374.58 mg Zn/kg dry excreta of hens. Similar results were observed with Cu. Added phytase significantly reduced the excreta content and the excretion of Cu. The results of this experiment indicate that adding 600 FTU to laying hen diets containing 14% CP decreases the excretion of Mg, Zn and Cu without any adverse effects on the egg mass produced of laying hens.