Abstract
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%.
Highlights
Mollusks rely on calcium for the growth of their shell and are highly dependent on calcium availability for survival. Harrison et al (1970) already reported the reduced growth rate, survival, and reproductive output of snails in low calcium environments
Chaitanawisuti et al (2010) indicated that the calcium needs of species belonging to Gastropoda class are higher than others
The results indicated that the daily weight gain and specific growth rate were highest in the Ca5 treatment (0.22 g/day and 2.17 %/day, respectively), and lowest in Ca9 (0.18 g/day and 2.02 %/day, respectively)
Summary
Mollusks rely on calcium for the growth of their shell and are highly dependent on calcium availability for survival. Harrison et al (1970) already reported the reduced growth rate, survival, and reproductive output of snails in low calcium environments. Harrison et al (1970) already reported the reduced growth rate, survival, and reproductive output of snails in low calcium environments. The growth and survival of species belonging to Gastropoda are affected when calcium levels decrease or come from a different origin (Oluokun et al, 2005; Egonmwan, 2008; Kouassi, 2008; Badmos et al, 2016; Binh et al, 2017). An experiment was developed to test different kinds of processed food diets and determine the appropriate calcium content to improve efficiency of the black apple snail grow-out period, while saving costs and reducing the impact on the water quality in the culture environment
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