DIETARY PHOSPHORUS REQUIREMENT OF FINGERLING LABEO ROHITA

Mohammad Musharraf* and Mukhtar Ahmad Khan
 
 Fish Nutrition Research Laboratory
 Department of Zoology
 Aligarh Muslim University
 Aligarh 202002, India
 mdmusharraf89@gmail.com

Indian major carp Labeo rohita, commonly known as rohu, is a fish species with demonstrated aquaculture potential. It is the prime fish cultivated in India and other Asian countries mainly as a component of polyculture systems with other indigenous and exotic carp species. It has a good demand and potential in most of the tropical markets because of its good taste and acceptability to prepared feeds. It grows to about 800-1000 g in less than a year. Although some aspects of the nutrient requirements of the Indian major carp L. rohita have been determined in the past, no information is available on dietary mineral requirement of fingerling L. rohita. The present study was, therefore, conducted to determine the dietary phosphorus requirement of fingerling L. rohita.

An eight-week feeding trail was conducted in eighteen 70-L indoor polyvinyl circular troughs (water volume 55 L)  provided with a water flow-through system (1-1.5 L/min) to  quantify the dietary phosphorus requirement of fingerling L. rohita (4.12±0.10 cm; 0.88±0.02 g). Six isonitrogenous and isocaloric purified diets (35 g/100g crude protein; 400 kcal/100g gross energy) with graded levels of phosphorus as 0.37 ( Basal diet without P supplement), 0.47, 0.57, 0.67, 0.77 and 0.87 g P 100 g-1 using calcium biphosphate, sodium phosphate and potassium biphosphate inclusion level at 50%, 25% and 25%, respectively, were formulated.  The experimental diets were hand-fed to triplicate group of fish thrice daily at 09:00, 12:00  and 17:00 hrs to apparent satiation for 8 weeks. Absolute weight gain (AWG), specific growth rate (SGR) and protein efficiency ratio (PER) increased significantly (P < 0.05) with increasing phosphorus level from 0.37 (D1) to 0.67 g (D4) P 100 g-1 and then levelled off (Table1) Dietary phosphorus levels significantly influenced whole-body protein, lipid and ash (P < 0.05). Whole-body, scale and vertebrae phosphorus content showed similar patterns as that obtained for absolute weight gain. The blood chemistry analysis showed that dietary phosphorus significant affected on serum phosphorus and alkaline phosphatase activity. Based on the growth performance, vertebrae and serum phosphorus concentration, optimum dietary phosphorus requirement is recommended to be 0.67 g P 100 g-1 for maximizing growth of fingerling L. rohita.