Article

Effects of Dietary Energy: Protein Ratio and Stocking Density on Growth and Survival of the Common Snapping Turtle Chelydra serpentinal1

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Abstract

Although the common snapping turtle Chelydra serpentina is cultured commercially in the United States, little information is available on nutritional and culture requirements. This study was conducted to evaluate the effects of dietary energy: protein ratio and stocking density on survival, growth, feed consumption, feed conversion, liposomatic index, dress-out percentage, and productive protein value of cultured, common snapping turtles. Hatchling turtles were stocked at 29 and 58 animals/m2 and fed one of seven prepared diets. Six diets contained 30, 35, or 40% protein at two digestible energy (DE) levels (7 or 9 kcal DE/g protein); the seventh was a reference diet (66% protein and 5 kcal DE/g protein) formulated to equal or exceed the whole-body essential amino acid composition of wild, common snapping turtles. Turtles stocked at 58/m2 exhibited greater mortality, lower weight gain, higher feed consumption, less-efficient feed conversion, lower liposomatic index, and lower productive protein value than turtles stocked at 29/m2 (P < 0.05). The reference diet produced the greatest weight gain (P < 0.001). The superior performance of turtles fed the reference diet suggests that: 1) the protein (amino acid) content and/or energy: protein ratio of the reference diet was superior to that of the other diets tested; 2) improvements in growth parameters can be made with dietary manipulation; and 3) high levels of plant protein can be used in prepared, snapping turtle diets.

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... The soft-shelled turtle (Pelodiscus sinensis) is a commonly cultured aquatic reptile species in China with a yield of more than 140,000 tons in 2004 (Shen et al., 2006;Zhang, 2005). Despite the fact that the aquaculture of this species is widespread, scientific studies concerning the effects of stocking density on biological characters are limited (Mayeaux et al., 1996). The objective of the present study is to evaluate the effect of stocking density on the energy budget of juvenile P. sinensis. ...
... In the present study, an obvious trend of decreased survivorship of juvenile soft-shelled turtle with elevated stocking density was observed. This agrees with the results of Mayeaux et al. (1996), who reported that common snapping turtles (Chelydra serpentine) stocked at 58 animals/m 2 exhibited greater mortality, lower weight gain, and higher food consumption compared to those stocked at 29 animals/m 2 . Food consumption also reduced with increasing stocking density in the present study, however, conflicting with the above snapping turtle results. ...
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The present work investigates the effect of stocking density on the energy budget of juvenile soft-shelled turtles (Pelodiscus sinensis). Turtles (body weight: 16.22±0.28 g) were stocked at densities of SD1 (8 animals/m 2 , 0.14 kg/m 2), SD2 (48 animals/m 2 , 0.81 kg/m 2) and SD3 (96 animals/m 2 , 1.62 kg/m 2) in aquaria in triplicate for each treatment. The experiment lasted for 35 days. Survival rate, coefficient of size variation, productivity, and apparent digestibility coefficient were not significantly different at the three stocking densities. While there were no significant differences between treatments SD2 and SD3, turtles in group SD1 showed a lower excretion rate and significantly higher food intake and growth rate. Turtles in group SD1 also showed higher crude lipid content and lower crude ash content. No significant differences were found among the treatments in body moisture and crude protein.
... Vitamin D production would not have been a factor in the laboratory study, as the incandescent basking lights used did not provide the appropriate light spectrum required for vitamin D production, and all necessary vitamins were provided in the prepared food. It is also possible that warmer years were correlated with higher protein availability because in snapping turtles, growth rate is positively related to protein content of food (Mayeaux et al., 1996). Unfortunately, we do not have data However, growth may not be detectably slowed until food is severely reduced. ...
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