Phosphorus requirement of Catla (Catla catla Hamilton) fingerlings based on growth, whole-body phosphorus concentration and non-faecal phosphorus excretion.

摘要

A 120-day feeding trial was conducted to determine the dietary requirement of phosphorus for Indian major carp, catla (Catla catla) fingerlings. Four hundred and eighty fingerlings (mean body weight: 4.23+or-0.87 g) were randomly distributed among eight treatment groups with three replicates each. Eight isonitrogenous and isocaloric semi-purified diets (crude protein: 35% and crude lipid: 8.5%) were formulated with graded levels of phosphorus using KH₂PO₄ (T₁: control, 0.1%; T₂: 0.3%; T₃: 0.5%; T₄: 0.7%; T₅: 0.9%; T₆: 1.1%; T₇: 1.3%; T₈: 1.5%) and fed to the respective groups. Twenty fish were stocked in 150 L plastic tanks and fed to apparent satiation twice a day. Specific growth rate (SGR) significantly (P<0.05) increased with increasing dietary phosphorus concentration from 0.73% to 1.27%, after which there was a slight decline in growth at 1.1% available phosphorus (aP) and remained constant thereafter. The quadratic broken-line model based on growth was Y=317.5-581(0.64-x) (0.64-x); R2=0.73. Moisture and crude protein contents of whole body were similar among all the treatments. However, the ether extract in T₁ group was significantly (P<0.05) higher than all the other treatments. The whole-body phosphorus content increased significantly (P<0.05) with an increase in phosphorus in the diets. The one-slope broken-line model based on whole-body phosphorus concentration was Y=4.07-1.63 (0.71-x); R2=0.48. The one-slope broken-line model for non-faecal phosphorus excretion as inorganic phosphorus (Pi) for 24 h revealed a trend of Y=12.67+73.96 (x-0.6); R2=0.81. Minimum aP requirements based on weight gain (%), whole-body phosphorus content and phosphorus excretion were 0.64%, 0.71% and 0.6%, respectively. Hence, the dietary aP requirement of catla fingerlings ranges from 0.6% to 0.71%.