Received: Feb 13, 2019 / Published: Aug 30, 2019
The present study was conducted to evaluate the effects of different dietary calcium levels on the growth and survival rate of black apple snails (Pila polita) in the grow-out period. There were 3 replicates for each treatment and the snails were fed with five calcium levels (% dry matter) in diet as follows: 1% (Ca1), 3% (Ca3), 5% (Ca5), 7% (Ca7), and 9% (Ca9). Two-month-old juveniles with an average initial body weight of 2.13g, shell height of 21.71mm, and shell width of 16.35mm were reared in tarpaulin tanks (1 × 1 × 1m; 40cm water depth) at the density of 100 individuals per tank. After 4 months of the rearing period, the average body weight, shell height, and shell width of the snails reached the highest values in the Ca5 treatment (28.43 g, 54.97 mm, and 40.09mm, respectively) and these values were significantly different compared to the remaining calcium contents (Ca1, Ca3, Ca7, and Ca9). The survival rate of the snails in Ca3 (75.7%) was higher than in Ca1 and Ca7 (74.7%), Ca5 (73.7%), and Ca9 (71.7%). However, the survival rate was not significantly different among the treatments. Snails in Ca5 obtained the highest productivity (2.88 kg m-2) and this value was significantly different from Ca1 (2.55 kg m-2) and Ca9 (2.35 kg m-2). The results of this study showed that the growth rate and productivity of black apple snails were highest when they consumed a diet containing 5% calcium. The optimum requirement of calcium for the black apple snails in the grow-out period was 4.51%.
