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The present study was designed to estimate the zinc (Zn) requirement of Labeo rohita juveniles fed practical diet. Treatments used for the study were consisted of six experimental diets supplemented with graded levels of Zn (0, 21, 42, 63, 84 and 104 mg/kg diet) from Zn gluconate. For each experimental diet, two replicates were allocated, and 18 fish were stocked in each replicate. The feeding trial was lasted for 90 days. Results showed that final weight, absolute weight gain, weight gain% and specific growth rate increased with increasing dietary Zn levels up to 42 mg/kg and started to decrease with further increase in dietary Zn level. Quadratic regression analysis of weight gain% data indicated that L. rohita juveniles required 62.58 mg/kg Zn for normal growth. Maximum Zn absorption was observed in fish fed diet supplemented with 42 mg/kg Zn compared with other dietary treatments. Alkaline Phosphatase (ALP) activity in kidney and spleen of L. rohita juveniles increased with the increase in dietary Zn levels up to 42 and 63 mg/kg, respectively. Conclusively, supplementation of graded levels of dietary Zn-gluconate improved the growth performance and increased the Zn bioavailability and ALP activity up to a certain limit in L. rohita juveniles.

The present research work was conducted to investigate the effects of microbial phytase and citric acid supplementations on nutrient digestibility performance by rohu (Labeo rohita) juveniles fed a sunflower meal (SFM)-based diet. The basal diet was supplemented with two levels of phytase (0 and 1000 FTU/kg) and each level of this phytase-supplemented diet was further supplemented with two levels of citric acid (0% and 2%). Chromic oxide (1%), as an inert marker, was added to the diet to determine nutrient digestibility. Results showed that digestibility of dry matter, crude protein and ether extract was significantly (p < .05) enhanced by citric acid supplementation. Similarly, phytase pretreatment also resulted in improved (p <.05) digestibility of dry matter, crude protein and ether extract. Also, citric acid and phytase supplementation improved (p < .05) the digestibility of P, Na, K, Ca, Mg, Cu, Zn, Mn and Fe. Nevertheless, the addition of both supplements (citric acid and phytase) simultaneously did not produce any interaction for the digestibility of these minerals. Hence, it is concluded that phytase (1000 FTU/kg) and citric acid (2%) supplementation to an SFM meal-based diet improved the nutrient digestibility inL. rohitajuveniles. [ABSTRACT FROM PUBLISHER]

The present feeding trial was conducted to assess the optimal level of phytase supplementation required for maximum nutrient absorption and growth performance ofLabeo rohitafingerlings fed canola meal-based diet. A standard diet having 30.21% protein and an energy value of 4.26 kcalg−1was used as reference diet. The experimental diet having similar protein and caloric density was formulated by using 70% reference diet and 30% of canola meal as test ingredient. This experimental diet was then divided into seven test diets and were supplemented by graded levels (0, 250, 500, 750, 1000, 1250 and 1500 FTU kg−1) of phytase enzyme. Chromic oxide was used in reference and test diets as an inert marker. Results showed that phytase supplementation at 750 FTU kg−1level effectively increased apparent digestibility coefficients of crude protein (64%), crude fat (76%) and gross energy (68%) as compared to reference and other phytase-supplemented diets. The results of present study showed increased growth and feed performance of fingerlings in response to phytase supplementation. Maximum performance was obtained by the fish fed on test diet having 750 FTU kg−1level. It was concluded that 750 FTU kg−1level of phytase supplementation in canola meal-based diet is sufficient for increasing nutrient digestibility and growth performance ofL. rohitafingerlings. [ABSTRACT FROM PUBLISHER]